Affiah Ekectrical Graphics

CHAPTER ONESKETCHING, DRAFTINGAND DRAWINGS.

1.1 Sketching

1.1.1 Technical Sketching

1.1.2 Sketching Materials

Many freehand sketches may be made to develop some of the detailsto arrive at some basic dimensions before a project is started and layout made.These sketches are useful in developing various ideas. Ideas originate in the mind,and to be useful they must be communicated to others. Many engineering ideasare far expressed in the form of a free Rand pencil sketches. Sketches show thefeatures of the device, serve as an aid in-performing related calculations. Inengineering drawing parlance sketches are either.i. Any freehand drawing regardless of the amount of detail shown (i.e.

complete drawings are sketches if draw without any instruments), andii. Any rough, quick, unfinished drawing i.e. a right edge and compass could be

used to show quickly and roughly the principal parts of a device. Generally,sketching refer to freehand drawing.

When a new project is being started an engineering meeting is usually held toresolve the various problems that arise, one of the best means of presenting newideas and approaches at such a meeting is through the use of technical sketches.The preliminary sketching of details to determine some ideas. Such sketches helpto establish tentative component placement and check calculations. They areuseful as layouts for the sketch or connection diagrams and the graph or charts, asa means of familiarizing persons handling specific details with the project as awhole. These sketches may be drawn in orthographic, isometric or projections,either in rough forms or sketched to a definite scale. Sketches are used temporarilyuntil regular drawing can be prepared; they should include title, date, draftsman'sinitials or name, job order number and similar information.

Material required for sketching are paper medium, soft pencil and eraser. A sketchpad or plane paper can be used, graph or cross-section paper is helpful in drawingstraight lines and approximating circles arcs and angles. Aclip pad is convenient

An image, drawn freehand, without the use of a straightedge or any othermechanical instrument, is a freehand sketch. Such sketches, though drawnquickly, effectively convey significant information if drawn with attention toproportion and accuracy. Freehand sketches are useful because they may beused to communicate ideas or designs to a coworker, your boss, or a client quicklyand simply.

1

to retain the sketch sheets and to provide sheets of paper and to provide a workingsurface. Transparent paper can be used to make prints of the sketches, so thatoriginal may be kept for reference and filing. Graph paper with non-producing linesis useful when it's desirable to have copies. A sketch with inside and out sidecalipers will help to maintain measurement.

It is important to obtain complete informationfor sketching purposes. For example, if a manufactured item is being examined,the name plate data, such as manufacturer's name and address the catalog andtype numbers, terminal markings, and colour coding of removable connectionsshould all be recorded. If an item is a part of the equipment, such details as over alldimensions, special tolerance and clearances should be noted; failure to record allthe required details can result in unnecessary details, especially if there is somedistance between the drafting room and the equipment being produced ormeasured. Considerable time and effort can be saved by obtaining all availabledata before starting a sketch for example the details of commercial componentscan be quickly formed in catalogue thus eliminating the need to take actualmeasurement. If complete identification of such component is provided, the sketchmay be simplified (or found unnecessary). The application of a sketch willdetermine the amount of detail required. If it conveys change in the information,dimensional notation can be reduced to minimum sometimes multi-view. TheSketch is advisable to bring out all cases as auxiliary views that may be required toillustrate positioning, dimensioning or a pictorial view to supplement the sketch.

1.1.3 Sketching ProcedureAlthough freehand sketches are drawn quickly, with only a pencil and paper, thisdoes not mean that the sketches are done carelessly. All lines should be clearlyvisible and the sketch easy to interpret. Freehand sketching requires simpleequipment: a pencil and some paper .

Graphite pencils are often used for sketching and drafting. There are a number ofgrades of graphite pencils available. The grade of the pencil indicates thehardness of the pencil. The grades range from 9H, the hardest pencil, to the verysoft EE. A 2H (hard) pencil works well for construction drawing while a 2B (soft,plus) may be useful for sketching and shading. When choosing a pencil, be sure toselect one that is hard enough to avoid smearing but not so hard that it will causegrooves in the paper even when used with normal pressure. If you wish to use onlyone pencil, a medium hard H will work well; you may make dark or light lines bysimply varying the pressure you use as you draw. This is also a good choice if youfind that drawings made with other grades of pencils tend to smear.

Pencils

2

Mechanical pencils, also known as lead holders, are popular with drafters. Suchpencils hold lengths of lead, allowing the drafter to have any length of the leadexposed. These pencil leads may be shaped, if desired, by rubbing the lead on afine sandpaper pad or file, just as for a wooden pencil lead.

Soft vinyl type erasers are recommended if you need to remove light pencilmarkings from your drawing. To avoid marring the finish of the paper, erasecarefully, along the direction of your work.

Plain paper is useful for most sketching. However, graph paper may makeaccurate sketching easier, especially if you are relatively new to sketching. Graphpaper is useful to maintain proportions when sketching. Avariety of graph paper isavailable. The most common type of graph paper is made of squares; however,special graph paper for particular kinds of drawings, such as isometric drawings, isalso available. If you find that the lines on graph paper "get in the way", you maywish to sketch on the back of the graph paper. Another option is dot paper, whichuses dots instead of lines. Below are links to different types of graph paper.

Erasers

Paper

1.2. DimensionsAnd NotesIn developing industrial drawing practice, it has been found that the most effectivemeans of communicating ideas and instructions is a combination of graphicalelements (lines and points) Numbers (dimensions and quantities), and words(materials and finishes). The graphical portion of the drawing provides the shapedescription; numbers in the form of dimensions and angles provide the sizedescription and lettered notes provide all other necessary information. Discussionon what should be included and here it should be presented must be based on ananalysis of the requirements of the user of the drawings. Some dimensionsindicate sizes, lengths, angles, location etc. The given dimensions must be thosenecessary to make the part and not those necessary to make the drawing.Information regarding the material to be used, the finish to be achieved and the fitto be provided between mating parts is included in the form of neatly lettered notes.Spinal instructions to the pattern maker, the machinist or the assembler may beincluded. The location, size, spacing, and even the form of the letters in the notesare carefully selected to provide a maximum legibility.

3

1. 3. DraftingAnd Design1.3.1 ProcedureThe drafting man must consider the existing shop facilities in case of fabricationand possibilities of lowering cost in design and drawing details are needed inspecification provision. He is also concerned with the products maintenance andrepairs. The constantly expanding nature of electrical/electronic drafting anddesign in which one is called to solve any problem makes the field interesting andprofitable one. Through the acquisition of techniques experience and knowledge,the draft man is likely to develop into a well trained capable designer. Thedraftsmen must begin by having information about basic drawing types; thedrawing may be classified into several categories and may further be sub-dividedinto other categories as will be discussed in the next section. These drawings are toprovide complete manufacturing details to the construction of equipment or of itsprototype. He must be able to prepare the various drawings in accordance with thegovernment and industry standards. To become an experiencedelectrical/electronic draftsman or designer and to perform work of this nature, hetmust have the idea of material and components with a knowledge ofelectrical/electronic theory. He is expected to be neat and very patient and able tovisualize any proposed construction or layout. He must have the ability to solveproblem during the course of his work. He should maintain an open attitude wordsnew development. The draftsman converts engineering ideas to workableproducts through the preparation of sketches, drawing and parts list. He isexpected to provide information pertaining to the purchase on raw material,components and hardware. He also acts as a link between engineers andtechnologist. His clear and understandable reading of paper's and information isrequired. His knowledge of components material and engineering terminologycomes to plays as he translates this information into various standardized type asgraphic symbols.

The same basic drawing instruments and materials are required inelectrical/electronics drafting work. As well as some specialized instruments andaccessories.

When an extensive ink work such as inking schematics or other drawings, a newtype of technical fountain pen such as radiographic save time and effort. The penhas several interchange points section for drawing various width, and can be usedwith French curves or templates as well as conventional straight line work.

1.3.2 Drafting Tools

Special Ink Instruments

4

Drawing Papers

1.3.3 Basic ComputerAided Drafting (CAD)

There are many or several drawing papers available. The selection of papersdepends on the importance and the ultimate use of the drawing. Using a poorquality material a frequently used to produce a complete assembly diagram willonly result in the drawing it again. Engineering drawing should be on transparentpaper, so that copies may be easily reproduced. Drawing papers should alsopossess stability, variation in temperature and humidity should be suitable forwriting by a pencil, pen as well as for typing and micro filming. There are fourmaterials available for drawings. They are (1) Bond paper (2) Vallon paper (3) Clothpaper (4) Polyester film paper.1.The Bond Paper: It is tracing paper less expressive but it lacks durability andtransparency. The only type that is suitable for pencil and ink work.2. Vallon Paper: Vallon is a rag paper that is been used to give greater transparency.3. Cloth Paper: It a coated liner, it resists better than the vallon paper and very goodfor micro filming purpose. Some grade are and made for either pencil or ink workand they are moisture resistant.Polyester film: This film is durable and is suitable for both pencil and ink and hastransparent resistance. It is also available for general drafting work and for printedand layout where extreme stability is required clear sharp line can be obtained witheither ordinary or special pencil.

The process of preparing engineering drawings on a computer is known ascomputer-aided drafting (CAD), and it is the most significant development to occurrecently in this field. It has revolutionized the way we prepare drawings. Thedrafting part of a project is often a bottleneck because it takes so much time.Drafter’s spend approximately two-thirds of their time “laying lead.” But on CAD,You can make design changes faster, resulting in a quicker turn-around time. CADalso can relieve you from many tedious chores such as redrawing. Once you havemade a drawing you can store it on a disk. You may then call it up at any time andchange it quickly and easily. It may not be practical to handle all of the draftingworkload on a CAD system. While you can do most design and drafting work morequickly on CAD, you still need to use traditional methods for others. For example,you can design certain electronics and construction projects more quickly on adrafting table. A CAD system by itself cannot create; it is only an additional andmore efficient tool. You must use the system to make the drawing; therefore, youmust have a good background in design and drafting. In manual drawing, you musthave the skill to draw lines and letters and use equipment such as drafting tablesand machines, and drawing aids such as compasses, protractors, triangles,

5

parallel edges, scales, and templates. In CAD, however, you don’t need thoseitems. A cathode-ray tube, a central processing unit, a digitizer, and a plotterreplace them.

Generating Drawings On CADACAD computer contains a drafting program that is a set of detailed instructions forthe computer. When you bring up the program, the screen displays each function orinstruction you must follow to make a drawing. The CAD programs available to youcontain all of the symbols used in mechanical, electrical, or architectural drawing.You will use the keyboard and/or mouse to call up the drafting symbols you need asyou need them. Examples are characters, grid patterns, and types of lines. Whenyou get the symbols you want on the screen, you will order the computer to size,rotate, enlarge, or reduce them, and position them on the screen to produce theimage you want. You probably will then order the computer to print the final productand store it for later use.

Engineering drawings show the relations between points, tines, surfaces,projections, holes etc, such drawing are useful and practical. Is a graphicallanguage that has been developed to record ideas and to transmit instructions.Drawings are used to tell how something looks, its nature (what it is like), how it isconstructed, assembled, connected up (assembled) taken apart. Just like a report,in each case the user determines the form, and requirements of the reader must bekept in mind. Drawings must always satisfy the requirements of the used henceaccepted convention must be used as much as possible with complete details.Companies and Government agencies make or prepare standard drawing toillustrate and list the details of such items commonly used in the electronicequipment, applications as hard-wares (nuts, screens and bolts) and components(capacitor, resistor, inductor) etc. In the military standard field these drawings areknown as MS.

Drawings may be classified into several categories andmay further be sub-divided into other categories; Pictorial, Mechanical, Outline,Instillation, Working/Shop, Assembly and exploded, Diagrammatic, Maintenance,Multi view, Construction and Electrical/Electronic drawings

A photograph provides a two dimensional picture of a three-dimensional object byintroducing a type of distortion (perspective).

1.4 The Graphical Language - Engineering Drawing

1.4.1 Types Of Drawings.

Pictorial Drawing

6

A picture represents the projection of the object into a single plane. When used byengineers, it indicates what the object looks like. The object can either be shown asit appears or will appear to the eye. Also, an aerial photograph results in mapswhich provides the best picture of what the view is really like.

When severalparts are joined together they form a unit known as such assembly, the drawingrepresenting such a unit is known sub assembly drawing. There is no sharp line ofdimension between such assembly and assembly drawing, assembly drawinggenerally show more part or may include one or more sub assembly that shows alarger unit.

An out line drawing is a simplified fashion of a detail drawing or of a sub assemblydrawing shows only the essential and the overall dimension such drawings arefrequently in trade technical publications to illustrate the shapes dimension andother characteristics of the part.

Some electronic items or equipment may required an installation drawing to showmounting details, over all dimensions wiring connection, and other information.This data may be required to install service or adjust the equipment, as well as toshow its relative location to other equipment.

Shop drawings are drawings and related data used to show some portion of thework prepared by the construction contractor, manufacturer, distributor, or supplier.Product data, such as brochures, illustrations, standard schedules, performancecharts, and other information, are furnished by the contractor or the manufacturerto show a material, product, or system for some portion of the work. EngineeringAids are sometimes required to draft shop drawings for minor shop and fieldprojects. These drawings may include shop items, such as doors, cabinets, andsmall portable buildings (prefabricated berthing quarters and modifications of

Mechanical DrawingThe complexity of electronic equipment determine the number of mechanicaldrawing needed to show the details of various parts components and assemblies ofthis parts and components. Regardless of whether the equipment complex orsimple. It design begins with the preparation of lay out drawing to show thepositioning of several major units that compose the equipment. After the layoutdrawing projection has been established. It is necessary to prepare detail drawingof each part using the layout drawing as a guard. The detail drawing shows theconstructional dimensions, finish and material to each part, if several part haveminor difference they may be shown on the same details drawing with thedifference indicated by dash number added to the drawing member.

Outline Drawings

Installation Drawings

Working (shop) Drawings

7

existing structures), or they may come from portions of design drawings,specifications, or freehand sketches given by the design engineer. Working from ashop drawing is much like working from other working drawings. You convert theideas you get from your interpretation of the lines and symbols into the productrepresented by the drawing.

inside another, but the drawing must be rapt as simple as possible to avoidconfusing the assembler. Sometimes, an exploded (blown-out) drawing is used tohelp the person who is not. trained to read engineering drawing. The pasts areusually numbered in the order that they are handled by the assembler.

The installation assembly and diagrammatic drawing have special applications inpiping and wiring. The piping drawing maybe semi pictorial, showing the contoursof pumps, piping, values etc or it may be a single-line diagram with units indicatedsymbolically. This type of drawing is used in exaction or installation, and the onlydimensions shown will be those needed for locating the individual components orfor showing over-all sizes. Electrical circuits are always shown diagrammaticallywith conventional symbols for resistors, motors, contactor, etc, such a SchematicDiagram is designed for clarity and in attempt is made to indicated location or size.In chemical engineering, flow diagrams used for layouts are examples ofdiagrammatic drawings.

Whenever a complex device is manufactured, specs instruction sheets must beprepared to guide the concerned with its operation and maintenance. Theseinstructions range in length from a few lines on a care to several large volumes. Inexplaining the operation and maintenance procedures, clear drawings are highlyeffective. In general, maintenance drawings are similar to institution assembles,

This is made to indicate how the various pasts go together in the complete unit. Itmay shone just the external features of the component pasts the mean of sectionviews, indicate internal features. It is frequently used by the design engineerindicate hone a device works and the functions of the components. It carries certaindimensions. Novel features are usually shown in great detail but standard parts willbe indicated by symbols only. In the drawings used for guiding the assembly ofcomplex units, only the information needed to show the relationship of parts isshown. The individual parts are not dimensioned, but clearances and distancesbetween centers are given. Section views are used to indicate how one part fits

Assembly and Exploded Drawing

Diagrammatic Drawings

Maintenance Drawings

8

however, special details are shown to guide the repairmen. Part are designated bycatalogue number to facilitate ordering, but dimensions and materials are notshown. Details are given on the adjustments which compensate for wear, and theclearances required for proper operation are indicated.

This is a combination of various views: front, back, top, bottom and sides giving anaccurate representation of an object to be shown in two dimensional paper. Theyshow hone accurately and object can be constructed Orthographic meansdrawings on the basis of points and lines projected at right angles to planes ofprojection Dotted lines are used to indicate hidden details.

Aconstruction drawing is any drawing that furnishes the information required by thecraftsmen to rough in equipment or erect a structure. The termsand are sometimes used interchangeably. Informationpresented in a set of working drawings, along with the specifications, should becomplete so the craftsman who uses them will require no further information.Working drawings show the size, quantity, location, and relationship of the buildingparts. Generally, working drawings may be divided into three main categories:architectural, mechanical, and electrical. Regardless of the category, workingdrawings serve several functions:(I). They provide a basis for making material, labor, and equipment estimatesbefore construction starts.(ii). They give instructions for construction, showing the sixes and location of thevarious parts. They provide a means of coordination between the different ratings.(iii). They complement the specifications; one source of information is incompletewithout the other when drawings are used for construction work.

Architectural drawings consist of all the drawings thatdescribe the structural members of the building and their relationship to each other.This includes foundation plans, floor plans, framing plans, elevations, sections,details, schedules, and bills of materials.

Aplan is actually a part of the architectural drawing that represents a view ofthe project from above. Two types of plans will be discussed here: plot plans andfloor plans.

A site plan includes not only the project but also the surrounding area.The project may be represented only by an outline, such as the one on the plotplan in figure 1.1. The north arrow symbol, used for orientation of the drawing, is

Multi View Or Orthographic Drawing

Construction Drawings

working drawingsconstruction drawings

Architectural Drawings:

Plans:

Site Plans:

9

shown. close coordination between the construction engineer/technician, theEngineering Aids, Equipment Operators, and Builders translates to the overallsuccess of the project. By looking over the plot plan, you will know what to do toprepare for the job.

Mechanical drawings include all drawings and notes thathave something to do with the water supply, sewage, drainage, heating andventilating, refrigeration, air conditioning, and gas supply systems. It may alsoinclude other drawings that are necessary to present the system properly inrelation to the other portions of the project.

Mechanical Drawings

prop

osed

bui

ldin

g

gate

EX

IS

TI

NG

RO

AD

Figure 1.1. Site plan showing proposed building.

10

These drawing show electrical inter-connection between the various componentsin an assembly or equipment or between the equipment units. Such drawing mayalso gain some of the mechanical features of the exact connection points and toclarify the operation of such components. In addition to the construction drawingsdiscussed above, you will be working with other types of electrical drawings ordiagrams. These drawings show the arrangement and relationship of parts.Electrical/Electronic diagrams are usually used to show how the parts of one ormore pieces of equipment are wired together. There are several types of thesediagrams. They are similar, yet different in some way. The short description of eachthat follows should enable you to recognize their differences.

: This shows the terminal to terminal wiring within the equipment.The control panel or other electronic assembly. Unlike the schematic diagram, theelectronic or the mechanical component are represented by their physical shaperather than by graphic symbol and are shown in their relative on their control panel,equipment assembly connection are shown point to point to that they represent theactual wire by were wiring of the equipment A wiring diagram is a detailed diagramof each circuit installation showing all of the wiring, connectors, terminal boards,and electrical or electronic components of the circuit. It also identifies the wires bywire numbers or color coding. Wiring diagrams are necessary to troubleshoot andrepair electrical or electronic circuits. The wiring diagram is almost a picturedrawing. It shows the wiring between components and the relative position of thecomponents. Figure 1.2 shows a wiring diagram of a motor, components areshown much as they would appear in a picture. The lines representing wires aremarked with numbers or letter-number combinations. Lines L1, L2, and L3 areincoming power leads. The diagram shows which terminals these power leads areconnected to in the motor starter. Leads connected to terminals T1, T2, and T3 arethe motor leads. The numbers without letters mark the control terminals of thestarter. Wiring diagrams are often used along with a list of repair parts. Wiringdiagrams may be of some help in troubleshooting circuit problems.

Electrical/Electronic Diagrams

Wiring Diagram

11

Figure 1.2. wiring diagram of a motor

12

The numbers without letters mark the control terminals of the starter. Wiringdiagrams are often used along with a list of repair parts. Wiring diagrams may be ofsome help in troubleshooting circuit problems.Also of importance is the connectionand terminal diagrams;

Figure 1.3 Connection Diagram

The in figure 1.3 shows all the internal and externalconnections. The circuitry can be traced more easily than on the wiring diagram.The components are still shown in their relative positions. This diagram can be usedto help you connect all the wiring and trace any part of the circuit. The connectiondiagram is a valuable troubleshooting tool. This type of diagram is often found

connection diagram

L3 L1 L2

STOP

START

OVERLOADRELAY

RESET

T2T 1

T3

MOTOR

M

OL2

13

inside the access cover of a piece of equipment. The is usefulwhen connecting wires to terminal boards, relays, switches, and other componentsof a circuit.An illustration is shown in figure 1.4.

The schematic is a diagram that represents the elements ofa system using abstract, graphic symbols rather than realistic pictures.Aschematicusually omits all details that are not relevant to the information the schematic isintended to convey, and may add unrealistic elements that aid comprehension. Forexample, a subway map intended for riders may represent a subway station with adot; the dot doesn't resemble the actual station at all but gives the viewerinformation without unnecessary visual clutter. A schematic diagram of a chemicalprocess uses symbols to represent the vessels, piping, valves, pumps, and otherequipment of the system, emphasizing their interconnection paths and

terminal diagram

Schematic Diagram:

Figure 1.4. Terminal diagrams.

B20D

B20E

B23D

B23E

B36B

B36C

B31A

B31B

B31C

B21A

B21A

TB1

TYPICAL TERMINAL

BOARD DIAGRAM

A

TYPICAL RELAY

TERMINAL DIAGRAM

B

5 4 3 2 1

BLK

GREEN

YELLOW

WHITE

RED

14

suppressing physical details. In an electronic circuit diagram, the layout of thesymbols may not resemble the layout in the physical circuit. In the schematicdiagram, the symbolic elements are arranged to be more easily interpreted by theviewer.A diagram combines some of the abstraction of a purelyschematic diagram with other elements displayed as realistically as possible, forvarious reasons. It is a compromise between a purely abstract diagram and anexclusively realistic representation.

Figure 1.6 One-line diagram of a motor control circuit.

1.5by a schematic diagram, the same motor control system shown in figures 1.1 - 1.3.This diagram is laid out in a way that makes the operation of the components easyto understand. This type of schematic diagram with the components laid out in aline is sometimes called a one-line or single-line diagram. Most schematicdiagrams are more complicated than this one. The more complicated ones can bebroken down into one-line diagrams, circuit by circuit. You can draw (or freehandsketch) your own one-line diagram by tracing only one circuit, component bycomponent, through a multi circuit schematic, using the symbols in figure 1.5. Yourown freehand sketches can help you understand other types of diagrams as well asthe schematic. You may vary these sketches to suit your needs. You may draw a

semi-schematic

The schematic or elementary diagram in figure 1.6 is a drawing that shows theelectrical connections and functions of a specific circuit arrangement. It facilitatestracing the circuit and its functions without regard to the physical size, shape, orrelative position of the component device or parts. The schematic diagram, like theconnection diagram, makes use of symbols instead of pictures. Figure shows,

L1M

0L STOP START

2

0LM

L1 STOP M

3

L3

L3

2

CIRCUIT “S”

CIRCUIT “M”

15

one-line diagram, using symbols, from a wiring diagram, an isometric diagram, or aconnection diagram, as long as all the necessary details are there for you to convertto lines and symbols.

Schematic diagrams are used extensively inrepair manuals to help users understand the interconnections of parts, and toprovide graphical instruction to assist in taking apart and rebuilding mechanicalassemblies. Many automotive and motorcycle repair manuals devote a significantnumber of pages to schematic diagram

A flow diagram or chart shows the sequence of operations orstages for a computer program or an industrial process. The name may have beenderived from various plans for the flow of water. The name of each operation orstage in a flow diagram is contained in a box or block, to simulate a process or areaof operation. The blocks are usually rectangular and are connected with singlelines to indicate the sequence of operation in a flow chart usually progresses fromthe top of the sheet to the bottom. Figure 1.7 shows a flowchart for the steps in themanufacture of an electronic chassis. It begins with the raw sheet steel and endswith the plated chassis to a storage area. The plating department block and everyother block may be further broken down into a departmental flowchart. The blocksshould all be drawing to the same dimensions. The block containing the mostlettering usually determines the size of all the blocks in a diagram. The flow lines

Schematic Diagram

Schematics in repair manuals:

Flow Diagrams:

Layout Principles:The following principles should be followed as closely as possible for layout ofschematic diagrams.1. Normal signal flow should be from left to right and from top to bottom.2. Large multistage diagrams may be laid out in layers; signal flow should be fromleft to right (or top to bottom).3. It is customary to begin with a rough sketch of diagram observing normal signalflow.4. Transistor and tube symbols should be aligned horizontally.5. When several similar components in (Resistors, coils, capacitors, etc) areconnected to a common bus they also should be aligned horizontally.6. When components are connected a parallel, the centers of the componentsymbols should be aligned horizontally.7. Uniform density of all graphic symbols is desirable, do not crows symbols in onearea while permitting large open areas to exist on a drawing.8. Letter and number all components to ensure that all are included in the finaldrawing in their proper location and connection in the schematic.

16

Figure 1.7. Chassis fabrication flowchart

Figure 1.8. Computer Flow Diagram

SHEET STEEL

PUNCH PRESS

DEGREASER

PLATING

INSPECTION

STORAGE

INPUT CONTROL OUTPUT

LOGIC

ARITHMETIC

MEMORY

17

are drawn with arrows to indicate the direction of flow between operation block.The arrows are usually drawn at the input side of the blocks but may also becentered on a flow line. The flow lines should not be staggered but must follow eachother vertically unless the chart is drawn to illustrate multiple flow paths. Whenmore than one flow line emerges from the side of a block, the lines should bespaced symmetrically.

Thisrepresents the component groups of component, or the units of the equipment in aseries of block or rectangle. It reduces the complex circuit in each stage ofequipment to single block form. The blocks should all be drawn to the samedimensions e.g. TV and Radio/Electronic watch block diagram shown in figure1.10a. A very simple single-line block diagram of a tuned radio frequency TRFreceiver. By Convention, the input or signal is drawn at the left side of the diagram.The Signal progresses through amplification and detection horizontally to the rightor output side of the diagram.

A logic block is defined by giving the output condition forevery possible combination of input conditions. Such input-output characteristicsare tabulated in a truth table. Note that the name of a logic block refers to the input-output characteristics. For example, the AND logic gate does not have a I outputuntil both A and B input lines are at a 1 level similarly, the OR logic gate has a 1output when a 1 level signal or pulse is applied to either theAor B inputs. The

Block Diagrams: These diagrams of electrical systems show major units of thesystem in block form. They are used with text material to present a generaldescription of the system and its functions. Block diagrams describe the functionaloperation of an electronics system in the same way they do in electrical systems. Inaddition, some electronics block diagrams provide information useful introubleshooting, which will be discussed later Block diagrams that break down thesimplified diagram into enough detail to show a fairly detailed picture of functionaloperation, but do not include wave forms, test points, and so on, are usually calledfunctional block diagrams. Graphic electrical and electronic symbols are frequentlyused in functional and detailed block diagrams of electronic systems to present abetter picture of how the system functions The distinction between flow diagramsand block diagrams is vague since common usage dictates the name given thediagram by a particular industry. In electronics a left-to-right convention exists, andthese system drawings are normally called block diagrams. The simplest electricalblack diagram or single-line diagram is intended to describe the basic functions of acircuit or output system. It usually does not include the detailed information andindividual parts identification of the schematic diagram as shown in figure 1.9.

.

.

Note:

Digital Logic Diagrams:

18

Figure 1.9. Block diagram of automotive starter and ignition systems.

basic shape of the inverter block in is a triangle. The triangle symbols indicate thatit is an amplifier. The digital logic designer builds a computer or control circuit bystarting with a few types of simple, basic circuits, called logic blocks. Many blocksare interconnected to perform the various computer functions. Although thenumerical input data to a computer are decimal numbers, the logic operationswithin the computer are performed in the binary member system. The binarynumber system uses only two digits, 0 and I. However, the tiny circle (or bobble) at

VOLTAGE

REGULATORDISTRIBUTOR

BATT STARTER ALT IGNSW

IGN

COIL

1

2

3

4

5

5

SPARK

PLUGS�

19

(a).

(b).

Radio/electronic watch block diagram. (b)

Circuit Diagram: A circuit diagram also known as an electrical diagram,elementary diagram, or electronic schematic is a simplified conventional graphicalrepresentation of an electrical circuit. A pictorial circuit diagram uses simpleimages of components, while a schematic diagram show the connections betweenthe devices, including power and signal connections.Arrangement of the

Figure 1.10.(a) single-line block diagramof a tuned radio frequency TRF receive.

the output symbolizes that the amplified output is inverted or reversed in polarity.For this reason, sometimes an inverter logic gate is called a NOT gate. One side ofthe triangle is always drawn vertically and is considered the input side of the black.Note that in the NAND logic gate symbol ( ), the output of an AND gate is invertedby the small bubble at the output. The acronym NAND means not-AND.

ο

Radio

frequency

employersDetector

Audio

frequency

amplifier

Antenna

Quart

Crystal BatteryDecoder

Network

oscillatorFrequency

DividerWareshaper

DigitalReadout

20

components interconnections on the diagram does not correspond to theirphysical locations in the finished device. Unlike a block diagram or layout diagram,a circuit diagram shows the actual wire connections being used. The diagram doesnot show the physical arrangement of components. A diagram does not show thephysical arrangement of components. A drawing with wires meant to depict whatthe physical arrangement of components they connect is called “artwork” or“layout” or physical “design.” Circuit diagrams are used for circuit design,construction of PCB layout and maintenance of electrical/electronic equipment.

Printed Circuit Drawing:

1.4.2 Electrical/ electronic Industry

one-line diagram

The printed at drawing is usually the art work required tolay out the printed circuit board which serves the function of mounting and interconnection by the various group that use such equipment e.g. laboratories.Industrial drawing use a different approach in circuit graphic symbols than thoseused in military and commercial electronic drawing. Commercial electronicsdrawing may depict electronic air craft equipment that has its own specificrequirement.

In the electrical industry, a schematic diagram is often used to describe the designof equipment. Schematic diagrams are often used for the maintenance and repairof electronic and electro-mechanical systems. Original schematics were done byhand, using standardized templates or pre-printed adhesive symbols, but todayElectrical CAD software is often used. More recently, with the progress of computertechnology, other representations were introduced and specialized computerlanguages were developed. Since with the explosive growth of the complexity ofelectronic circuits, traditional schematics are becoming less practical. Schematicsfor electronic circuits are prepared by designers using EDA (Electronic DesignAutomation) tools called schematic capture tools or schematic entry tools. Inelectric power systems design, a schematic drawing called a isfrequently used to represent substations, distribution systems or even wholeelectrical power grids. These diagrams simplify and compress the details thatwould be repeated on each phase of a three-phase system, showing only oneelement instead of three. Electrical diagrams for switchgear often have commondevice functions designate by standard function numbers.

When these symbols are seen in a manual, be alert to the potential for personalinjury. Follow the recommended precautions and safe operating practices included

1.5. Wiring Diagram & Schematic SafetyAlert Symbols.

21

with the alert symbols. Safety notices in any manual provide important information.Read and be familiar with these instructions before attempting installation,operation, or maintenance. Failure to observe these precautions could result inserious bodily injury, damage to the equipment, or operational difficulty. The safety-alert symbols are:

ANSI Z535 encourages the use of safety symbols that communicate a comparablemessage to the worded message on the sign or label. The safety symbol whenselected properly, should identify:

* The hazard* Identify a means of avoiding the hazard* Or identify the consequences of not avoiding the hazard.

The safety symbol should clarify or reinforce the worded message on the label.When safety symbols are being used they should be as simple as possible andshould contain only essential details. They should be easy to learn and torecognize.There are four types of safety symbols described inANSI Z535.5 2007.

* HazardAlerting* MandatoryAction

Warning Alerts users to potential physical danger or harm. Failure tofollow warning notices could result in personal injury or death.

Caution Directs attention to general precautions, which if not followed,could result in personal injury and/or equipment damage.

Note Highlights information critical to your understanding or use of theproduct.

!

22

* Prohibition* Information

When using safety symbols to comply with ANSI, the symbol can be black on awhite background, other colors may be used, like safety red for fire related symbols,green for emergency equipment, etc. To comply with both ANSI Z535.4 and ISO3864 Standards simultaneously, then, the following applies, ISO 3864 2002standards require that all of the safety symbols used on international product safetylabels be within a surround shape, yellow equilateral triangle with black innerborder for hazard alerting symbols, blue circle for mandatory actions, and red circlewith 45° degree slash for prohibition symbols. ANSI Z535.4 2007 does not requiredthe use of a yellow equilateral triangle or the mandatory surround shape but, it doesrecognize it and permits their use.

Area of the safety sign that contains the signal word. For personalinjury hazards, the signal word panel must contain the safety alert symbol. A signalword is selected according to the risk of harm presented by the hazardous situationthat the safety message addresses. That is, signal word selection is based on therisk posed if the safety message is not followed. This is the word that calls attentionto the safety sign and designates a degree or level of hazard seriousness. Thesignal words for product safety labels are: " ", " ", " "and " ". See figure 1.11.

A symbol which indicates a potential personal injury hazard.It is composed of an equilateral triangle surrounding an exclamation mark. Thesafety alert symbol shall not be used to alert persons to property-damage-onlyaccidents see figure 1.12..

Signal Word:

DANGER WARNING CAUTIONNOTICE

Safety Alert Symbol:

Figure1.11. Signal Word

DANGER!DANGER! WARNING! WARNING!

!CAUTION! NOTICECAUTION CAUTION

23

Figure 1.12. SafetyAlert Symbols

For use with DANGER signal word: white triangle, red exclamation mark and redback ground.

For use with WARNING signal word: black triangle with orange exclamation mark.

For use with CAUTION signal word: black triangle with yellow exclamation mark.

For use with DANGER, WARNING or CAUTION signal words: yellow background,black border and black exclamation mark.

For use with DANGER, WARNING or CAUTION signal words: yellow background,black border and black exclamation mark with a yellow border around the blackborder.

Warning:

Caution:

Danger, Warning, Caution Black border:

Danger, Warning, Caution Yellow border :

Safety Symbol:Safety symbols are graphic representations chosen to clearly convey a specificalerting message. The conveyed message of a safety symbol is to describe thetype of hazard, potential consequences of the hazard, or evasive/avoidanceactions to be taken. When used, the Safety Symbol shall be compatible with theword message. See figure 1.13.

24

Figure 1.13 Safety symbols

ISO allows the use of symbol only labels and/or safety symbolswith supplementary text labels. When a product safety label contains a singlesymbol, the layout of the product safety label should use one of the surroundshapes below. The surround shape and color is determined by the type of safetysymbol: HazardAlerting, Prohibition, MandatoryAction or Information

Surround Shape:

Figure 1.x Surround shapes

There are 2 basic types of safety symbols for use on safety signs, labels and tags:hazard alerting and hazard avoidance.HazardAlerting Symbols:Awell developed hazard description pictorial should

ANSI Z535

Safety Symbols

ISO 3864-2

Safety Symbols

Hazrdd Identification Prohibition Mandatory Action Information:Safety Condition

Information:Fire Safety

25

clearly identify the hazard and portray the potential consequences of a failure tofollow instructions. See figure 1.14.

HazardAlerting SymbolsFigure 1.14

Hazard Avoidance Symbols: Should clearly identify the actions necessary to avoidinteraction of persons with the hazard. See figure 1.15.

Figure 1.15 Hazard avoidance symbols.

26

2.0. ElectricalAnd Electronic Schematic Symbols.

2.1. Wires and connections.

.

CHAPTER TWOBASIC ELECTRICALAND ELECTRONICSCHEMATIC SYMBOLS AND REGULATORYAGENCIES.

Circuit symbols are used in circuit diagrams which show how a circuit is connectedtogether. The actual layout of the components is usually quite different from thecircuit diagram. To build a circuit you need a different diagram showing the layout ofthe parts on strip-board or printed circuit board. In order to understand thefunctioning of an electrical or electronic circuit, you must be able to "read" theschematic diagram of that circuit. A schematic diagram is the road map of thecircuit. In order to get from one point to another, you must be able to follow theappropriate route and understand the meanings of the various symbols foundalong the way. Symbols are used to indicate conductors, resistors, switches,motors, transistors, and other electrical and electronic parts. Components in acircuit schematic are generally represented by such a symbol and/or a letterdesignator.

Figure 2.1 wires and crossing conductors

( a) Wires

( b) Wires joined

( c ) Wires not joined

27

Basic to any schematic diagram is the use of straight lines to indicate conductors.The conductor is the "roadway" of the circuit map. The conductors interconnect thecomponents of the circuit. Conductors often cross paths with one another in thecircuit. This may occur with or without their making electrical contact. Figure 2.1illustrates the typical methods for wires and crossing conductors within a schematicdiagram.2.1a: To pass current very easily from one part of a circuit to another.2.1b: A 'blob' should be drawn where wires are connected (joined), but it issometimes omitted. Wires connected at 'crossroads' should be staggered slightlyto form two T-junctions, as shown on the right.2.1c: In complex diagrams it is often necessary to draw wires crossing even thoughthey are not connected. I prefer the 'bridge' symbol shown on the right because thesimple crossing on the left may be misread as a join where you have forgotten toadd a 'blob'!There are many types of conductors used in electrical and electronic circuits. Theymay range from the thin layers of metal foil used in printed-circuit boards to heavycables used in power transmission. Cables generally consist of two or moreconductors, usually in the same insulation jacket.Aspecial type of conductor foundin many electronic applications is the shielded wire or coaxial cable. Here, theconductor is surrounded by a metallic shield to protect against interference fromadjacent electrical influence. The shielding on the cable may or may not begrounded. Figure 2.2 shows some common symbols for shielded conductors.

Figure 2.2. Shielded Conductors

UngroundedGrounded

28

2.2. Basic Components: There are literally hundreds of different types ofelectrical and electronic components in use today. However, three components arewidely used in a wide variety of applications. These three components are found inmost circuit schematics of any complexity. The three components are (a) resistors;(b) capacitors; and (c) inductors.Resistors. Resistors are unquestionably the most commonly used circuitcomponents. They are found in almost every electrical and electronic schematicdiagram. Resistors are appropriately named in that they are designed to "resist" theflow of electrical current. Resistors are typically shown in schematics by the symbolillustrated in figure 2.3. In addition to the symbol, the resistor is generally labeled bythe letter "R" followed by a number, e.g., R1, R2, etc. The resistance value,measured in ohms, may also be indicated. If the resistance is not indicated, youcan determine it by observing the color coding used on most resistors.

(d) Variable Resistor(Preset)

(a) Fixed Resistor

( b) Variable Resistor(Rheostat)

( c) Variable Resistor(Potentiometer)

29

Figure 2.3a: A resistor (fixed resistor) restricts the flow of current, for example tolimit the current passing through an LED. A resistor is used with a capacitor in atiming circuit. Some publications still use the old resistor symbol:

Figure 2.3b: This type of variable resistor with 2 contacts (a rheostat) is usuallyused to control current. Examples include: adjusting lamp brightness, adjustingmotor speed, and adjusting the rate of flow of charge into a capacitor in a timingcircuit.Figure 2.3c: This type of variable resistor with 3 contacts (a potentiometer) isusually used to control voltage. It can be used like this as a transducer convertingposition (angle of the control spindle) to an electrical signal.Figure 2.3d: This type of variable resistor (a preset) is operated with a smallscrewdriver or similar tool. It is designed to be set when the circuit is made and thenleft without further adjustment. Presets are cheaper than normal variable resistorsso they are often used in projects to reduce the cost.

Resistor color codes.How to read Resistor Color Codes:The 4-band code is used for marking low precision resistors with 5%, 10% and 20%tolerances. Identifying the value will become easy with a little practice, as there areonly a few simple rules to remember:1. The first two bands represent the most significant digits of the resistance value.Colors are assigned to all the numbers between 0 and 9, and the color bandsbasically translate the numbers into a visible code. Black is 0, brown is 1, red is 2and so on (see the color code table below). So, for example, if a resistor has brownand red as the first two bands, the most significant digits will be 1 and 2 (12).2. The third band indicates the multiplier telling you the power of ten to which thetwo significant digits must be multiplied (or how many zeros to add), using the sameassigned value for each color as in the previous step. For example, if this band isred (2), you will multiply it by 10² = 100 (or add 2 zeros). So, for the resistor we usedin the previous example, the value would be: 12 x 100 = 1200? (1.2k?).Note: If the multiplier band is gold or silver, the decimal point is moved to the left byone or two places (divided by 10 or 100).3. The tolerance band (the deviation from the specified value) is next, usuallyspaced away from the others, or it's a little bit wider. A color is assigned to eachtolerance: gold is 5%, silver is 10%. 20% resistors have only 3 color bands - thetolerance band is missing.

30

The standard resistor color code table:Color 1st digit 2nd digit 3rd digit* Multiplier Tolerance T e m p .

Black 0 0 0 ×100Brown 1 1 1 ×101 ±1% (F) 1%Red 2 2 2 ×102 ±2% (G) 0.1%Orange 3 3 3 ×103 0.01%Yellow 4 4 4 ×104 0.001%Green 5 5 5 ×105 ±0.5% (D)Blue 6 6 6 ×106 ±0.25%©Violet 7 7 7 ×107 ±0.1% (B)Gray 8 8 8 ×108 ±0.05% (A)White 9 9 9 ×109Gold ×0.1 ±5% (J)Silver ×0.01 ±10% (K)None ±20% (M)

* 3rd digit - only for 5-band resistorsSo, for a 560 ohm, 5% resistor the color stripes will be green, blue, brown and gold.Green and blue are the first significant digits (56); brown is the multiplier (101 = 10)and gold is the tolerance (5%). 56 x 10 = 560?.If the 3rd band would be red instead of brown, the multiplier would be (102 = 100)instead of 10 and the resistor value would be 56 x 100 = 5600 ohms = 5.6 k ohms.If the multiplier band is gold or silver, then the decimal point is moved to the left oneor two places (divided by 10 or 100). For example, a resistor with green, blue, silverand gold rings has a value of 56 x 0.01 = 0.56?.

The 5 band code is used for marking high quality, precision resistors with 2%, 1% orlower tolerances. The rules are similar to the previous system; the only difference isthe number of digit bands. The first 3 bands will represent the value, the 4th bandwill be the multiplier and the 5th stripe will give us the tolerance.

A few resistors have an additional band - often giving beginners a bit of trouble -indicating either the reliability or the temperature coefficient. The reliability bandspecifies the failure rate per 1000 hours (assuming that a full wattage being appliedto the resistor). This stripe is found primarily on 4-band resistors made for militaryapplications and seldom used in commercial electronics.

The 5-band code

Optional band

31

The temperature coefficient is more commonly marked, especially on quality 5-band resistors, as it starts to become an important factor for precision components.For a resistor with temperature coefficient of 200 ppm, for example, a change intemperature of 50°C causes a value change of 1%. The most common values forthis band are presented in the color chart above.

Examples:

Green, blue, red, with silver tolerance band: 56 x 100 = 5.6 k with a tolerance of10%Brown, black, orange, gold tolerance band: 10 x 1000 = 10000 ohms (or 10K ),with a tolerance of 5%Red, red, brown, silver tolerance band: 22 x 10 = 220 ohms (220 ohms), with atolerance of 10%More 4 band resistor color code examples: E12 and E24 series.

Blue, brown, white, brown, red tolerance band: 619 x 10 = 6190 ohms (6.19K ),with a tolerance of 2%Red, red, brown, black, with a brown tolerance band: 221 x 1 = 221 ohms, with atolerance of 1%Brown, black, black, red, with a brown tolerance band: 100 x 100 = 10000 ohms(10.0K ), with a tolerance of 1%.

Resistors are available in standard values such as 1K, 2.2K, 4.7K, and so on. Thetwo most common standards are the E12 and E24. You will notice that in the E12series each succeeding value falls within +/- 10% of the previous value. The E24range includes all of the E12 values, plus a further 12 to enable the selection of moreprecise resistances.The E6 (20%) range is a subset of the E12 (10%) range and the E12 range is asubset of the E24 (5%) range. Similarly, the E48 (2%) range is a subset of the E96(1%) range and the E96 range is a subset of the E192 (0.5% or less) range. Note,that the E24 range is technically also a subset of the E48 range, however, becauseof the different number of digits used for representation and rounding errors, thecorresponding values in the two series do not match.E6 series: (20% tolerance)10, 15, 22, 33, 47, 68E12 series: (10% tolerance) - examples...10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82

Four band code:

Five band code:

Standard EIADecade Resistor Values

Ω

Ω

Ω

Ω

32

E24 series: (5% tolerance) - examples...10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82,91E48 series: (2% tolerance) - examples...100, 105, 110, 115, 121, 127, 133, 140, 147, 154, 162, 169, 178, 187, 196, 205,215, 226, 237, 249, 261, 274, 287, 301, 316, 332, 348, 365, 383, 402, 422, 442,464, 487, 511, 536, 562, 590, 619, 649, 681, 715, 750, 787, 825, 866, 909, 953E96 series: (1% tolerance)100, 102, 105, 107, 110, 113, 115, 118, 121, 124, 127, 130, 133, 137, 140, 143, 147,150, 154, 158, 162, 165, 169, 174, 178, 182, 187, 191, 196, 200, 205, 210, 215,221, 226, 232, 237, 243, 249, 255, 261, 267, 274, 280, 287, 294, 301, 309, 316,324, 332, 340, 348, 357, 365, 374, 383, 392, 402, 412, 422, 432, 442, 453, 464,475, 487, 491, 511, 523, 536, 549, 562, 576, 590, 604, 619, 634, 649, 665, 681,698, 715, 732, 750, 768, 787, 806, 825, 845, 866, 887, 909, 931, 959, 976

The resistance value could be stamped or painted on the body of the through-holeresistor, no? Yes, but the numbers would be quite small and difficult to read. Also,the markings would easily rub off or become smeared with time. Old, clear-markedresistors were less confusing for the beginners, but - for example - if such a resistoris mounted with the marked side down, you cannot read its value unless you take itout of the circuit. The resistor color code might seem a bit confusing and ratherinconvenient at first, but most electronics hobbyists and technicians are surprisedwhen they realize how quickly they've memorized the color chart without the use ofmnemonics or other silly shortcuts. The color code is quite intuitive, and after a brieffamiliarization period, it's quite easy to use, it will become almost a second nature.

Examples:

Yellow, violet, black -- 47 ohm 20%Orange, orange, brown --> 330 ohm 20%Brown, black, red --1k 20%

Green, blue, red, gold -- 5.6kohm 5%Red, yellow, orange, gold -- 24kohm 5%Blue, gray, yellow, silver -- 680k 10%More 4 band resistor color code examples: E12 and E24 series.

Red, yellow, orange, black, brown -- 243 ohms, 1% precision 5-band resistorYellow, violet, gold, gold, yellow -- 4.7 ohms, 5% - this resistor is calculated with the

3 bands:

4 bands:

5 bands:

33

4-band rule (the yellow band is ignored).Orange, black, black, brown, brown -- 3.00 k ohms, 1% - note: this is a non-standard1% (E96) resistor, but some manufacturers make every value from the E24 serieswith 1% tolerance!More: 5 band E48 (2%) series resistor color code examples.

Red, red, brown, brown, brown, red -- 2.21k, 1% 50ppm/°CWhite, black, white, brown, red, red -- 9.09k, 2% 50ppm/°C-If you are using the online resistor color code calculator do not enter the last band(red in the two examples above).

6 bands:

Capacitors: Capacitors are the most common components found in schematicdiagrams. Capacitors are capable of storing electrical charges. They have theability to block direct current (DC) while passing alternating current (AC). Thestandard symbols used to represent fixed capacitors are shown in figure 2.4. Inaddition to the symbol, a capacitor is generally labeled with the letter "C." The valueof the capacitor may also be indicated. The basic unit of capacitance is the farad;but most practical capacitors will be rated in microfarads ( F) or picofarad (PF). Aswith resistors, if the value is not given, determine it by observing the color codingfound on many types of capacitors. Figure 2.5 is a table indicating the use of colorcoding for some capacitors.

Figure 2.4. Capacitor types.

μ

(d) Trimmer Capacitor

(a) Fixed Capacitor (b) Capacitor, polarized

( c) Variable Capacitor

34

Figure 2.4:(a). A capacitor stores electric charge. A capacitor is used with a resistor in a timingcircuit. It can also be used as a filter, to block DC signals but passAC signals.

(b).Acapacitor stores electric charge. This type must be connected the correct wayround. A capacitor is used with a resistor in a timing circuit. It can also be used as afilter, to block DC signals but passAC signals.

( c).Avariable capacitor is used in a radio tuner.

(d). This type of variable capacitor (a trimmer) is operated with a small screwdriveror similar tool. It is designed to be set when the circuit is made and then left withoutfurther adjustment.

Capacitor Number Code

102472J

Capacitor Colour Code

brown, black, orange

wide red, yellow

Real capacitor values (the E3 and E6 series)

Anumber code is often used on small capacitors where printing is difficult:the 1st number is the 1st digit,the 2nd number is the 2nd digit,the 3rd number is the number of zeros to give the capacitance in pF.Ignore any letters - they just indicate tolerance and voltage rating.

For example: means 1000pF = 1nF (not 102pF!)For example: means 4700pF = 4.7nF (J means 5% tolerance).

A colour code was used on polyester capacitors for many years. It is now obsolete,but of course there are many still around. The colours should be read like theresistor code, the top three colour bands giving the value in pF. Ignore the 4th band(tolerance) and 5th band (voltage rating).For example:

Note that there are no gaps between the colour bands, so 2 identical bands actuallyappear as a wide band.

For example:

Whyis this? Imagine that you decided to make capacitors every 10 F giving 10, 20, 30,40, 50 and so on. That seems fine, but what happens when you reach 1000?

means 10000pF = 10nF = 0.01μF.

means 220nF = 0.22μF.

You may have noticed that capacitors are not available with every possible value,for example 22μF and 47μF are readily available, but 25μF and 50μF are not!

μ

35

Figure 2.5. Capacitor color code.

It would be pointless to make 1000, 1010, 1020, 1030 and so on because for thesevalues 10 is a very small difference, too small to be noticeable in most circuits andcapacitors cannot be made with that accuracy. To produce a sensible range ofcapacitor values you need to increase the size of the 'step' as the value increases.The standard capacitor values are based on this idea and they form a series whichfollows the same pattern for every multiple of ten.

150, 220, 330, 470, 680, 1000 etc. Notice how this is the E3 serieswith an extra value in the gaps. The E3 series is the one most frequently used forcapacitors because many types cannot be made with very accurate values.

While not used as extensively as resistors and capacitors, inductors (or coils) arestill a common basic componentof many electrical and electronic circuits. Aninductor has the property of opposing a change in the existing current.

Inductors:

The E3 series 10, 22, 47,

The E6 series 10, 15, 22, 33, 47, 68,

(3 values for each multiple of ten) ... then it continues 100,220, 470, 1000, 2200, 4700, 10000 etc. Notice how the step size increases as thevalue increases (values roughly double each time).

(6 values for each multiple of ten) ... then itcontinues 100,

CAPACITANCE

COLOR 1ST DIGIT 2ND DIGIT MULTIPLIERTOLERANCE(PERCENT)

VOLTAGE RATING

1ST DIGIT 2ND DIGIT

BLACK 0 0 1 �20 0 0

BROWN 1 I 10 1 1

RED 2 2 100 2 2

ORANGE 3 3 1,000 3 3�30

YELLOW 4 4 10,000 5 5�40

GREEN 5 5 100, 000 4 4�5

BLUE 6 6 1,000. 000 6 6

VIOLET 7 7 7 7

GRAY 8 8 8 8

WHITE 9 9 9 9�10

36

The standard symbol for an inductor is shown in figure 1-9. Inductors are generallylabeled with the letter "L" and are rated in henrys, the basic unit of inductance. Inmost practical applications, the actual rating will be given in millihenrys ormicrohenrys.

Figure 1-9.Air Core Inductor.

A coil of wire which creates a magnetic field when current passes through it. It mayhave an iron core inside the coil. It can be used as a transducer converting electricalenergy to mechanical energy by pulling on something.

Every electrical circuit must have a source of electrical power. Some electricaland/or electronic devices have an internal power source, but most rely on someexternal source to supply the power necessary to operate them. When the powersource is external to the particular schematic diagram being examined, generallyonly the connectors bringing in the power are identified and labeled with theappropriate originating source. However, when the source of the power for a givencircuit is internal to the schematic, it must be identified and represented by theappropriate schematic symbol. Most electrical and electronic equipment isoperated by "plugging" it into an external power source, or by some installed powersource (usually a battery).As previously stated, external power sources are usuallyidentified on a schematic diagram by their point of entry into the circuit.

Another common source of power for electrically powered equipment is thegenerator. Simply put, generators convert mechanical energy to electrical energy.Depending on the design and construction of the generator, the output may be setto meet the needs of the equipment supplied. Generators may be designed toprovide either AC or DC power. AC generators are often referred to as alternators.Figure 2.7 shows the standard symbols used to represent generators or alternatorsin schematics.

Power Sources:

Generators:

Inductor(Coil, Solenoid)

37

Figure 2.6. Power supplies.Figure 2.6:(a). Supplies electrical energy. The larger terminal (on the left) is positive (+). A singlecell is often called a battery, but strictly a battery is two or more cells joined together.(b). Supplies electrical energy. A battery is more than one cell. The larger terminal(on the left) is positive (+).(c ). Supplies electrical energy. DC = Direct Current, always flowing in one direction.(d). Supplies electrical energy. AC = Alternating Current, continually changingdirection.(e).Asafety device which will 'blow' (melt) if the current flowing through it exceeds aspecified value.

(e) Fuse

(a) Cell (b) Battery

( c) DC supply (d) AC supply

�

38

Figure 2.8. Generators.

Although transformers are not a true power source, they are often the source of thevoltages used in a given circuit. Typically, an external power source is applied to atransformer, which converts the input power to the voltage(s) necessary to operatethe circuit supplied. Transformers are a special application of inductors, thus thesimilarity in the schematic symbol used. Figure 1-13 illustrates several types oftransformers used in a variety of circuits.

Like transformers, power supplies are not a true power source. They generally takean input from an external, power source and convert that source to usable voltages t

Transformers:

Power Supplies.

Figure 2.9. Transformer

G Gen

Generator (general)

GGenerator, direct - current

� �Generator, alternating - current

G

39

o operate the circuits they supply. Typically, a power supply will convert anAC inputinto one or more DC outputs. Most power supplies consist of four basic sections: atransformer; a rectifier; a filter; and a regulator Power supplies may be designed to

produce one or several different output voltages. Depending on the complexity ofthe circuit demand, power supplies may be fairly simple or they may be quiteextensive. Often the power supply for a circuit will require a separate schematicdiagram to illustrate the components and functional operation of the power supply.

Many electrical and electronic circuits include controls and indicators to assist theoperator in the use and repair of the equipment. These controls may consist ofdevices such as switches, relays, fuses, plugs and jacks, test points, andindicators. These operator aids are normally represented in the circuit schematicdiagram to illustrate their effect on the circuit operation.

give the operator control over the operation of the equipment. Bypositioning the switch, the operator directs the operation of the circuit by routing thedirection of electrical signals within the circuit. Switches may be simple, such as anon/off switch, or they may be complex, being of multi position/multifunction design.They may be designed to be momentary action, to latch in a given position, make-before-break, or to perform any number of specific functions. While the possibledesigns for switches are almost limitless, figure 2.9 illustrates several commonlyused switch symbols. In addition to the symbol, switches are normally labeled withthe letter "S." A special type of switch is the circuit breaker. Circuit breakersnormally act as on/off switches as well as providing over voltage/overcurrentprotection to the circuit.

rather than being controlled manually by the operator, a relay is operatedelectrically by energizing a coil to realign the contacts of the relay and re-route theelectrical signals. Relays may be indicated in schematics only by their coil and itsenergizing source, only by the contacts used by the particular circuit, or by both.Contacts are normally shown in the position with the relay de-energized, unlessotherwise indicated.

Plugs and jacks are generally used to connect the equipment to some externaldevice, or to interconnect circuits and components within the equipment. Plugs andjacks may be single conductor or multiconductor. They may be permanent orremovable, shielded or unshielded. Jacks and plugs often provide a convenientmeans to check or test critical signals. This provides an extremely useful function introubleshooting. Where it is impossible or impractical to check a signal at a jack or

.

Controls:

Switches and Relays.Switches

Relays

Plugs, Jacks, and Test Points:

40

Figure 2.9. Switches and relays.

(g) Relay

(a) Push Switch(push-to-make)

(b) Push-to-Break Switch

( c) On-Off Switch(SPST)

(d) 2-way Switch(SPDT)

(e) Dual On-Off Switch(DPST)

(f) Reversing Switch(DPDT)

NO

COM

NO

41

Figure 2.9:(a). A push switch allows current to flow only when the button is pressed.This is the switch used to operate a doorbell.(b). This type of push switch is normally closed (on), it is open (off) only whenthe button is pressed.(c ). SPST = Single Pole, Single Throw.An on-off switch allows current to flowonly when it is in the closed (on) position.(d). SPDT = Single Pole, Double Throw. A 2-way changeover switch directsthe flow of current to one of two routes according to its position. Some SPDTswitches have a central off position and are described as 'on-off-on'.(e). DPST = Double Pole, Single Throw. A dual on-off switch which is oftenused to switch mains electricity because it can isolate both the live andneutral connections.(f). DPDT = Double Pole, Double Throw. This switch can be wired up as areversing switch for a motor. Some DPDT switches have a central offposition.(g). An electrically operated switch, for example a 9V battery circuitconnected to the coil can switch a 230V AC mains circuit. NO = NormallyOpen, COM = Common, NC = Normally Closed.

plug, circuits are often designed to provide test points. These test points may beinternal to the circuit or tapped off and provided at an external point. Figure 2.10illustrates some typical symbols used for jacks, plugs, and test points. Jacks arelabeled with the letter "J"; plugs with the letter "P"; and test points with the letters"TP." With multiconductor plugs and jacks, the individual conductors are generallyidentified by pin or pin socket numbers.

Figure 2.10. Test points and Connections.

COMMON

CONNECTIONS CONTACTS

FEM. MALE

MULTIPLE.

MOVABLE

COAXIALRECEPTACLE

COAXIAL PLUG

FEMALE MALE

MULTIPLE.FIXED

230 V

117 V

CONNECTORS

TP

TP

TESTPOINTS

42

Indicators: Indicators are generally placed in electrical or electronic circuits toprovide the operator a status of some function of the equipment. The indicator maybe audible, visual, or both. Audible indicators may consist of a horn, buzzer,speaker, or other noise producing device. Most often these devices are used asalarms or warnings. Visual indicators are typically some type of a light, dial, ormeter. Visual indicators may provide a warning or present some type of status. Seefigure 2.11.

Figure 2.11. Indicators

Light Indicators.

AW P

V

G

Audible Indicators.

Dials and meters

43

Solid State Devices: Solid-state devices may be represented symbolically by thesymbols shown in figure 2.12 and 2.13. Solid-State Devices. Solid-state devices(sometimes referred to as semiconductors) have, to a large extent, replacedvacuum tubes in the design of most modern electronic equipment. Solid-statedevices are generally made of silicon or germanium that is "doped" with impuritiesto provide the desired conductivity.

They may be doped to produce either p-type material (positive) or n-type material(negative). These semiconductors are used in the place of vacuum tubes due tothese advantages: they are smaller, take less power to operate, usually cost less,and are more rugged.

(d) Zener Diode

(a) Diode(b) Light Emitting Diode

(LED)

( c ) Photodiode

Figure 2.12. Diodes

Figure 2.13. Transistors.

(a) Transistor NPN (b) Transistor PNP ( C) Phototransistor

44

The most common of these solid-state devices is the transistor. While there arenumerous variations, most transistors are either pnp transistors or npn transistors.Figure 2.13a and b shows the symbol for a npn and a pnp transistor. The key torecognizing a npn or pnp is the direction of the arrow on the emitter. On the pnptransistor symbol, the arrow points inward; on the npn, the arrow points outward.Another solid-state component the diode is consists of one piece of p-typematerial and one piece of n-type material formed together to create a p-n junction.This p-n junction has the property to pass current in only one direction. Diodes arealso designed in a number of variations to meet special applications. Figure 2.12shows the schematic symbol for some commonly used diode applications.Transistors and diodes may be constructed in a variety of designs to meet theneeds of special applications. some of the more common special purpose solid-state symbols are shown in figure 2.14. The symbols shown are as follows:(i) Silicon-controlled rectifier (SCR).(ii) Silicon-controlled switch (SCS).(iii) Triac.(iv) Field-effect transistor (FET).(v) Unijunction transistor (UJT).

Figure 2.14. Special applications devices.

(a) SCR (b) SCS. © Triac.

(d) FET. (e) UJT.

45

Transistor Codes

European (Pro-Electron) coding letters.

Transistor types are coded either by the US MIL specifi cation or by the European (Pro-Electron) lettering system. The US system starts with 2N followed by a code number;the 2N portion identifi es the device as a transistor (1N indicates a diode). The fulldescription can be found only if you can identify the manufacturer by looking up thecode number. The European system, used for all types of semiconductors, uses two orthree letters followed by a number. The letters indicate the type of device, with thenumbers indicating how recent the design is. Table 8.1 shows the meanings of theletters.

The first letter indicates the semiconductor material used:A GermaniumB SiliconC Gallium arsenide and similar compoundsD Indium antimonide and similar compoundsR Cadmium sulphide and similar compounds

The second letter indicates the application of the device:A Detector diode, high speed diode, mixer diodeB Variable capacitance (varicap) diodeC AF (not power) transistorD AF power transistorE Tunnel diodeF RF (not power) transistorG MiscellaneousL RF power transistorN PhotocouplerP Radiation detector (photodiode, phototransistor, etc.)Q Radiation generatorR Control and switching device (such as a thyristor)S Switching transistor, low powerT Control and switching device (such as a triac)U Switching transistor, high powerX Multiplier diode (varactor or step diode)Y Rectifi er, booster or effi ciency diodeZ Voltage reference (Zener), regulator or transient suppressor diode.

The figures or letters following indicate the design.Athree-figure serial number is usedfor ‘consumer types’, used in domestic radio, television, tape-recorders, audio, etc.A

46

serial consisting of a letter (Z Y, X, W, etc.) followed by two figures means a device forprofessional use (transmission, etc.). The European system is much more informative,because you can tell the type of device immediately from the code. The 1N, 2N systemtells you only whether the device is a diode or a transistor. AF: audio frequency; RF:radio frequency.

2SA PNP transistor2SB PNP Darlington2SC NPN transistor2SD NPN Darlington2SJ P-channel MOSFET or JFET2SK N-channel MOSFET or JFET3SK Dual-gate N-channel FETs

Japanese transistor coding

Logic Gates:

Logic gates process signals which represent true (1, high, +Vs, on) or false (0, low,0V, off). There are two sets of symbols: traditional and IEC (InternationalElectrotechnical Commission). There are two primary types of digital gates, withseveral variations; AND Gates: The AND gate is a digital circuit designed toproduce a high level output when all input levels are high. If any of the input levels islow, the output of the gate will be low. OR Gates: The OR gate is designed toproduce a high level output when any one of the input levels is a high level. Toprovide variations to the two basic gates, inverters are used at either the input or theoutput of the gate. The inverter is used to change the logic level of the input oroutput from a high to a low, or from a low to a high. When the inverter is used with thebasic gate, only the small circle of the inverter symbol is used in the schematicdiagram. An AND gate with an inverter at its output result in a NAND gate whereasan inverter at the output of an OR gate will produce a NOR gate. See figure 2.15 fordetails.

47

Gate

Type

Traditional

SymbolIEC Symbol Function of Gate

NOT

A NOT gat e can only have one

input. The 'o' on the output means

'not'. The output of a NOT gate is

the inverse (opposite) of its input, so

the output is true when the input is

false. A NOT gate is also called an

inverter.

ANDAn AND gate can have two or more

inputs. The output of a n AND gate

is true when all its inputs are true.

NAND

A NAND gate can have two or more

inputs. The 'o' on the output means

'not' showing that it is

a Not AND gate. The output of a

NAND gate is true unless all its

inputs are true.

OR

An OR gate can have two or more

inputs. The output of an OR gate is

true when at least one of its inputs is

true.

NOR

A NOR gate can have two or more

inputs. The 'o' on the output means

'not' showing that it is

a Not OR gate. The output of a

NOR gate is true when none of its

inputs are true.

EX-OR

An EX -OR gate can only have two

inputs. The output of an EX -OR

gate is true when its inputs are

different (one true, one false).

EX-

NOR

An EX -NOR gate can only have two

inputs. The 'o' on the output means

'not' showing that it is a Not EX -

OR gate. The output of an EX -NOR

gate is true when its inputs are the

same (both true or both false).

Figure 2.15. Two input logic gates Types.

1=

&

&

�1

�1

�1

�1

48

2.3. Other Symbols:

Grounds:

Figure 2.16. Ground Connections.

Chassis

Antennas:

Motors:

Many other symbols exist and may be found on schematic diagrams. It would beimpractical to attempt to illustrate them all.

The circuit return or completion is normally accomplished through theuse of grounds. Grounds are usually of two types:(1) Earth ground is a direct conducting connection to the earth or some structure.The symbol used to represent earth ground is shown in figure 2.16.

ground is a conducting connection to the chassis or frame of theequipment or circuit. The chassis ground may not be at the same potential as theearth ground. The symbol for a chassis ground is shown in figure 2.16b.A third symbol may be used to indicate a ground connection when all identicallyannotated return connections are at the same potential. The symbol for thesecommon-ground connections is shown in figure2.16c

Many electronic devices require the use of an antenna to receive inputsignals. The types of antennas used vary greatly, based on the function of theequipment. Figure 2.17 illustrates some of the common symbols used for antennas.

Many electrical or electronic circuits are affected by drive motors. Motorsare the electrical opposite of generators, theys convert electrical energy tomechanical energy. Like generators, motors may be either AC or DC. Figure 2.18shows the symbols for motors.

( c) Common(a) Earth (b) Chasis

49

Figure 2.17. Antenna Symbols.

50

Figure 2.20. Motor Types.

( c) A.C Motor(a) General (b) D.C Motor

M M M�

51

2.4. RegulatoryAgencies and Organizations.The national electrical code:

National fire protection association:

The NEC establishes regulations for the installation of electrical conductors,equipment, raceways, and signaling and communications systems. The codecovers public and private premises including homes, buildings and structures,mobile homes, recreational vehicles, and floating buildings. Installation locationsinclude yards, parking lots, carnivals, and industrial substations. The NEC alsosets standards for the installation of conductors and equipment that connect toelectricity supplies, and installations used by electrical utilities such as officebuildings, garages, warehouses, machine shops, recreational buildings, and otherstructures that are not an integral part of generating plants, substations, or controlcenters. Below are the definitions of key NEC terms;• ARTICLE – a segment of the Code focused on a specific topic. Artides arenumbered and divided by Sections numbered as subsets. Example: Article 100,Section 100.1• CODE – An extensive compilation of provisions covering broad subject matter orthat is suitable for adoption into law independently of other codes and standards.• FPN – Abbreviation for Fine-Print Note which supplements an Article’s rules.FPNs are not requirements and are for information purposes only.• MANDITORY – A provision of the NEC that must be followed by law. Mandatoryrules are marked by the word “shall.”• STANDARD –Adocument that contains only mandatory provisions which use thework “shall” to indicate requirements and that is in a form generally suitable formandatory reference by another standard or code, or that is for adoption into law.Nonmandatory provisions are located in the appendix, footnotes, or fine-print noteand are not considered a part of the requirements of a standard.

The NEC is only one of several standardized safety volumes published by theNFPA. The NFPA is a U.S. organization developed to create and maintainminimum standards and requirements for fire prevention, fire suppression,training, and other life-safety codes.All types of subjects are covered from buildingcodes, emergency response methods, and investigations, to personal protectiveequipment (PPE) for both electrical tradesmen and firefighters. Publications arenumbered for identificationand include the following:NFPA70—National Electrical CodeNFPA70B—Recommended Practice for Electrical Equipment MaintenanceNFPA70E—Standard for Electrical Safety in the Workplace

52

NFPA72—National FireAlarm CodeNFPA79—Restriction ofAccess to Hazardous EnergyNFPA 101—Life Safety Code NFPA 704—Standard System for the Identification ofthe Hazards of Materials for Emergency ResponseNFPA853—Standard for the Installation of Stationary Fuel Cell Power SystemsNFPA921—Guide for Fire and Explosion InvestigationsFees received from these technical manuals and other material finance the NFPA.The NFPA was originally formed in 1896 by a group of insurance representativeswho thought it prudent to establish standards for the emerging market of firesprinkler systems. Within a year, the NFPA's focus broadened to the developmentof regulations for fire protection in another fast-growing technology—buildingelectrical systems. From there it developed codes for all aspects of building designand construction.

The IEEE, administers the National Electrical Safety Code (NESC) that sets theground rules for practical safety codes for people involved in the installation,operation, or maintenance of electric supply and communication lines andequipment. At first glance, this might seem like a duplication of material covered inthe NEC; however, each code covers uniquely different aspects of electricalinstallations. While the NEC is focused on hazards arising from the use of electricityin buildings and structures, the NESC is designed to bring consistency and safetyto the design, construction, operation, and use of electric supply andcommunication installations. Excluded from the standards covered by the NESCare installations in mines, ships, railway rolling equipment, aircraft, automotiveequipment, and utilization wiring.From 1973 to 1993, the NESC was revised every 3 years. Beginning with the 2002edition, the NESC began issuing updated publications every 5 years, with the nextscheduled revision due in 2012. The NESC is made up of subcommittees that areresponsible for the content of the NESC. Subcommittee section assignments areas follows:Subcommittee 1—Coordination (Sections 1, 2, and 3; coordination betweentechnical subcommittees)Subcommittee 2—Grounding Methods (Section 9)Subcommittee 3—Electric Supply Stations (Sections 10-19)Subcommittee 4—Overhead Lines—Clearances (Sections 20-23)Subcommittee 5—Overhead Lines—Strength and Loading (Sections 24-27)Subcommittee 7—Underground Lines (Sections 30-39)Subcommittee 8—Work Rules (Sections 40-43)

National electrical safety code:

53

As with the NEC, the NESC is written as a voluntary standard. However, someeditions and some parts of the code have been adopted, with and without changes,by somel authorities.

The ANSI is a nonprofit organization that oversees the development of voluntarystandards for products, services, processes, systems, and personnel in the UnitedStates. The organization also coordinates U.S. standards with internationalstandards so that American products can be used worldwide. For example,standards make sure that people who own cameras can find the film they need forthem anywhere around the globe. The ANSI mission is to enhance the globalcompetitiveness of U.S. business and the U.S. quality of life by promoting andfacilitating conformity and voluntary consensus standards and maintaining theirintegrity. ANSI accredits standards that ensure consistency among thecharacteristics and performance of products, that people use the same definitionsand terms regarding materials, and that products are tested the same way. ANSIalso accredits organizations that certify products or personnel in accordance withrequirements that are defined in international standards.The institute is like the umbrella that covers thousands of guidelines that directlyimpact businesses in almost every sector. Everything from construction equipment,to dairy standards, to energy distribution, and electrical materials is affected. ANSIis also actively engaged in accrediting programs that assess conformance tostandards, including globally recognized programs such as the ISO 9000 QualityManagement and ISO 14,000 Environmental Systems. Accreditation by ANSIsignifies that a procedure meets the Institute's essential requirements foropenness, balance, consensus, and due process safeguards. For this reason,American National Standards are referred to as “open” standards

The Occupational Safety and Health Administration (OSHA) is a United StatesDepartment of Labor agency. Unlike other organizations such as NESC or ANSI,OSHA is not publically run, but is comprised of private company representatives.OSHA's statutory authority extends to non governmental workplaces where thereare employees. The mission of OSHA is to prevent work-related injuries, illnesses,and deaths by issuing and enforcing standards for workplace safety and health,providing training, outreach, and education, establishing partnerships, andencouraging continual improvement in workplace safety and health. This meansthis agency oversees regulations that affect both employers and employees. TheOccupational Safety and HealthAdministration publishes regulations by which

American national standards institute :

Occupational SafetyAnd HealthAssociation (OSHA):

54

safety in the workplace are measured.

The International Electrotechnical Commission (IEC) is a worldwide organizationfor standardization comprising all national electrotechnical committees (IECNationalCommittees). The object of IEC is to promote international co-operation onall questions concerning standardization in the electrical and electronic fields. Tothis end and in addition to other activities, IEC publishes International Standards,Technical Specifications, Technical Reports, Publicly Available Specifications(PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparationis entrusted to technical committees; any IEC National Committee interested in thesubject dealt with may participate in this preparatory work. International,governmental and non-governmental organizations liaising with the IEC alsoparticipate in this preparation. IEC collaborates closely with the InternationalOrganization for Standardization (ISO) in accordance with conditions determinedby agreement between the two organizations.Examples of these codes is as follows;IEC 60027(all parts) --------------------------Letter symbols to be used in electrical technology.IEC 60617------------------------ Graphical symbols for diagrams.IEC 61175---- 1993------------- Designations for signals and connections.IEC 81714-2-- 1998------------ Design of graphical symbols for use in thetechnical documentation of products -Part 2:Specification for graphical symbols in a computer-sensible form including graphical symbols fora reference library.extracted from the codes published as a compilation in ISO Standards Handbook,Quantities and units.

material on which data can be recorded and from which data can be retrieved.[ISO/IEC 2382-1]

fixed and structured amount of information intended for human perception that canbe managed and interchanged as a unit between users and systems.NOTES:1. The term document is not restricted to its meaning in a legal sense.

The International Electrotechnical Commission (IEC):

Basic terms:data medium

document

55

2.Adocument can be designated in accordance with the type of information and theform of presentation, for example overview diagram, connection table, functionchart.3. A document may appear in a static manner on paper and microform ordynamically on (video) display devices. [ISO/IEC 8613-1]

information, represented graphically in accordance with agreed rules and usually toscale.

collection of documents related to a given subject[IEC 62023,]

collection of data organized according to a conceptual structure describing thecharacteristics of the data and the relationships among their corresponding entities,supporting one or more application areas.[ISO/IEC 2382-1]

active link from a point in a document to another point in the same document or inanother document.1.Ahyperlink is only available in documents presented on video screens.2. The hyperlink implies that a user can activate the link in order to get to the otherpoint.

identifier of a specific object with respect to the system of which the object is aconstituent, based on one or more aspects of that system.[IEC 61346-1]

reference designation assigned with respect to the object of which the specificobject is a direct constituent.[IEC 61346-1]

set of reference designations of which at least one unambiguously identifies theobject of interest.[IEC 61346-1]

graphical representation depicting the shape, size, etc. of a physical part orassembly drawing showing a horizontal view, section or cut

2)

drawing (technical)

documentation

database

hyperlink

reference designation

single-level reference designation

reference designation set

pictorial form

diagram

56

graphical representation depicting, by the use of graphical symbols and outlineswith inscriptions, the relations among the objects of a system or of a productincluding the interconnections

2)graphical presentation of an installation with respect to its surrounding topography

2)graphical presentation describing the behavior of a system, for example therelations between two or more variable quantities, operations or statespresentation form using columns and rows.

map

chart, graph

Reference designationsAreference designation is a combination of letters and numbers used to identify thevarious parts and components on electronic drawings, diagrams, parts lists, and soon. For objects having a reference designation or a reference designation set inaccordance with IEC 61346-1, at least one unambiguous reference designationshall be shown at every representation of the object. The reference designationshall be readable from the bottom edge of the page and should be located above orto the left of the object representation, see IEC 81714-2 for further details. Areference designation shall be presented on a single line. The referencedesignation set may be presented on a single line or on successive lines; if thereference designations are presented on successive lines each referencedesignation shall start on a new line; If more than one reference designation ispresented on the same line, and if not clearly separated for example as in a table,the character SOLIDUS ( / ) shall be used as the separator sign between thedifferent reference designations; The order of the presented referencedesignations in a reference designation set has no significant meaning.

57

CHAPTER THREE

Electrical symbols used on an architectural plan show the location and type ofelectrical device required. The National Electrical Codes describes outlet as a pointon a wiring system where current is taken to supply utilization equipment. Areceptacle outlet is “an outlet where one more receptacles are installed,” figure 3.1.A lighting outlet is “an outlet intended for it direct connection of a lamp holder, alighting fixture, or a pendant cord terminating in a lam holder,” figure 3.2. A toggleswitch is not an outlet. The term outlet is used broadly by electrician to includenoncurrent-consuming switches an similar control devices in a wiring system whenestimating the cost of the installation. Each type o outlet is represented on the plansas a symbol. The NEC defines a device as “a unit of an electrical system which isintended to carry but no utilize electric energy.’The outlets an shown by the symbolsfrom a floor plan in figure 3.3.

ELECTRICAL SYMBOLSAND OUTLETS

3.1. Introduction

always allow at least 6 inches offree conductor at all outlets andjunctions so as to be able to workeasily with the wiring devices to beinstalled.

the 6 inches is measured fromfront edge of box

Figure 3.1 Receptacle outlet

58

A study of residential electrical plans shows that many different electrical symbols areused to represent the electrical devices and equipment used in the building. Designersand electrical engineers use standard symbols wherever possible but many plans maycontain symbols that are not found in the standards; when such nonstandard andunlisted symbols are used, we must refer to the for the interpretation of thesesymbols.

legend

figure 3.2 lamp holder

figure 3.3 fig. Use of electrical symbols and notation on floor plans.

whiteblack

S3

S3

59

3.2. Graphic Electrical Wiring SymbolsDrafting PracticesApplicable to Graphic Electrical Wiring Symbols.A.

B.

C.

D.

E.

1.2.

3.

4.

5.

6.

Electrical layouts should be drawn to an appropriate scale or figure dimensionsnoted. They should be made on drawing sheets separate from the architectural orstructural drawings or on the drawing sheets for mechanical or other facilities.Clearness of drawings is often reduced when all different electric systems to beinstalled in the same building area are laid out on the same drawing sheet. Clearness isfurther reduced when an extremely small drawing scale is used. Under thesecircumstances, each or certain of the different systems should be laid out on separatedrawing sheets. For example, it may be better to show signal system outlets andcircuits on drawings separate from the lighting and power branch circuit wiring.

Outlet and equipment locations with respect to the building should be shown asaccurately as possible on the electrical drawing sheets to reduce reference toarchitectural drawings. Where extremely accurate final location of outlets andequipment is required, figure dimensions should be noted on the drawings. Circuit andfeeder run lines should be so drawn as to show their installed location in relation to thebuilding insofar as it is practical to do so. The number and size of conductors in the runsshould be identified by notation when the circuit-run symbol doesn’t identify them.

All branch circuits, control circuits, and signal system circuits should be laid out incomplete detail on the electrical drawings, including identification of the number, size,and type of all conductors.

Electric wiring required in conjunction with such mechanical facilities as heating,ventilating and air-conditioning equipment, machinery, and processing equipmentshould be included in detail in the electrical layout insofar as possible when itsinstallation will be required under the electrical contract. This is desirable to makereference to mechanical drawings unnecessary and to avoid confusion as toresponsibility for the installation of the work.

A complete electrical layout should include at least the following on one or moredrawings:

Floor plan layout to scale of all outlet and equipment locations and wiring runs.A complete schedule of all of the symbols used with appropriate description of the

requirements.Riser diagram showing the physical relationship of the service, feeder and major

power runs, units substations, isolated power transformers, switchboards, panelboards, pull boxes, terminal cabinets, and other systems and equipment.

Where necessary for clearness, a single line diagram showing the electricalrelationship of the component items and sections of the wiring system.

Where necessary to provide adequate information elevations, sections and details ofequipment and special installations and details of special lighting fixtures and devices.

Sections of the building or elevation of the structure showing floor-to-floor, outlet, and

60

equipment heights, relation to the established grade, general type of buildingconstruction, etc. Where practical, suspended ceiling heights indicated by figuredimensions on either the electrical floor plan layout drawings or on the electricalbuilding section or elevation drawings.

Where necessary to provide adequate information, plot plan to scale, showing therelation of the building or structure to other buildings or structures, service poles,service manholes, exterior area lighting, exterior wiring runs, etc.

In the case of exterior wiring systems for street and highway lighting, area drawingsshowing the complete system.

Any changes to the electrical layout should be clearly identified on the drawingswhen such changes are made after the original drawings have been completed andidentified on the drawing by a revision symbol.

7.

8.

9.

61

3.3. A list of lighting outlet symbols.

1.1 Surface or pendant incandescentmercury vapor or similar lamp fixture

1.2 Recessed incandescent mercuryvapor or similar lamp fixture

1.3 Surface or pendant individualfluorescent fixture

1.4 Recessed individual fluorescentfixture

1.5 Surface or pendantcontinuous-row fluorescent fixture

1.7 Bare-lamp fluorescent strip**

1.6 Recessed continuous-row fluorescentfixture*

Ceiling Wall

R R

R

R

62

*In the case of combination continuous-row fluorescent and incandescentspotlights, use combinations of the above standard symbols.**In the case of continuous-row, bare-lamp fluorescent strip above an area-widediffusing means, show each fixture run, using the standard symbol; indicate area ofdiffusing means and type by light shading and/or drawing notation.

1.12 Outlet controlled by low-voltageswitching when relay is installed inoutlet box

1.8 Surface or pendant exit light

1.9 Recessed exit light

1.10 Blanked outlet

1.11 Junction box

(continued)

X X

XR XR

B B

J J

L L

63

Receptacle Outlets: Symbols for Receptacle Outlets.

Ungrounded Grounding

2.1 Single receptacle outlet.

2.2 Duplex receptacle outlet.

2.3 Triplex receptacle outlet.

2.4 Quadruplex receptacle outlet.

2.5 Duplex receptacle outlet—splitwired.

2.6 Triplex receptacle outlet—splitwired.

2.7 Single special-purposereceptacle outlet.*

2.8 Duplex special-purposereceptacle outlet.*

2.9 Range outlet.

2.10. Special-purpose connection or provisionfor connection. Use subscript letters to indicatefunction (DW - dishwasher, CD- cloths dryer, etc.

G

G

G

G

G

G

G

G

RG

GDW

* *

* *

DW

R

64

(continued)

*Use numeral or letter either within the symbol or as a subscript alongside thesymbol in the drawing list of symbols to indicate type of receptacle or usage.

Ungrounded Grounding

2.11 Clock hanger receptacle.

2.12 Fan hanger receptacle

2.13 Floor single receptacle outlet.

2.14 Floor duplex-receptacle outlet

2.15 Floor special-purpose outlet.*

2.16 Floor telephone outlet—public.

2.17 Floor telephone outlet—private.

F CG

C FG

G

G

G

* *

65

Switch Outlets: Symbols for Switch Outlets

S 3.1 Single-pole switch

S 3.2 Double-pole switch

S 3.3 Three-way switch

S 3.4 Four-way switch

S 3.5 Key-operated switch

S 3.6 Switch and pilot lamp

S 3.7 Switch for low-voltage switching system

S 3.8 Master switch for low-voltage switching system

S 3.9 Door switch

S 3.10 Time switch

S 3.11 Circuit breaker switch

S 3.12 Momentary contact switch or pushbutton for other thansignaling

2

3

4

K

P

L

LM

D

T

CB

MC

3.13 Switch and single receptacle

3.14 Switch and double receptacle

3.15 Ceiling pull switch

S

S

S

66

Circuiting:Wiring method identification by notation on drawing or in specificationSymbols for Circuiting

Note: Use heavy-weight line to identify service and feeders. Indicate empty conduitby notation CO (conduit only). Unless indicated otherwise, the wire size of thecircuit is the minimum size required by the specification. Identify different functionsof wiring system, e.g., signaling system, by notation or other means.

4.1 Wiring concealed in ceiling or wall.

4.2 Wiring concealed in floor.

4.3 Wiring exposed

4.4 Branch circuit home run to panel board.Number of arrows indicates number ofcircuits. (A numeral at each arrow may beused to identify circuit number.)Note: Anycircuit without further identificationindicates two-wire circuit. For a greaternumber of wires, indicate with cross lines.4 . 5

4.6 Wiring turned down.

W i r i n g t u r n e d u p

3 wires

4 wires

2 1

67

Symbols for Panel boards, Switchboards, and Related Equipment:

5.1 Flush-mounted panel board and cabinet.*

5.2 Surface-mounted panel board and cabinet.*

5.3 Switchboard, power control center, unitsubstations* - should be drawn to scale.

5.4 Flush-mounted terminal cabinet.*(In small-scale drawings the TC may beindicated alongside the symbol.)

5.5 Surface-mounted terminal cabinet.*(In small-scale drawings the TC may beindicated alongside the symbol.)

5.6 Pull box. (Identify in relation to wiring sectionand sizes.)

5.7 Motor or other power controller.*

5.8 Externally operated disconnection switch.*

5.9 Combination controller and disconnectionmeans.*

*Identify by notation or schedule.

TC

TC

68

Signaling System Outlets: Residential OccupanciesPresented here are signaling system symbols for use in identifying standardizedresidential-type signal system items on residential drawings where a descriptivesymbol list is not included on the drawing. When other signal system items are to beidentified, use the basic symbols presented here for such items together with adescriptive symbol list.

Signaling System Symbols for Residential Occupancies.

6.1 Pushbutton

6.2 Buzzer

6.3 Bell

6.4 Combination bell-buzzer

6.5 Chime

6.6 Annunciator

6.7 Electric door opener

CH

D

69

6.8 Maid’s signal plug

6.9 Interconnection box

6.10 Bell-ringing transformer

6.11 Outside telephone

6.12 Interconnecting telephone

6.13 Radio outlet

6.14 Television outlet

BT

R

TV

M

70

Bus Ducts and WirewaysSymbols for Bus Ducts and Wireways

Electric Distribution or Lighting System, Underground:Symbols for Underground Electric Distribution or Lighting System

7.1 Trolley duct*

7.2 Bus way (service, feeder, or plug-in)*

7.3 Cable trough ladder or channel*

7.4 Wire way*

8.1 Manhole.*

8.2 Transformer manhole or vault.*

8.3 Transformer pad.*

T T T

B B B

C C C

W W W

M

TP

TM

71

(Continues)

Electric Distribution or Lighting System Aerial:Symbols for Electric Distribution or Lighting System Aerial.

8.4 Hand hole.

8.5 Underground direct burial cable. (Indicate type,size and number of conductors by notation or schedule.)

8.6 Underground duct line. (Indicate type, size, andnumber of ducts by cross-section identification of eachrun by notation or schedule. Indicate type, size, andnumber of conductors by notation or schedule.)

8 . 7 S t r e e t l i g h t s t a n d a r d f e e d f r o munderground circuit.*

9.1 Pole*

9.2 Street light and bracket*

9.3 Transformer*

9.4 Primary circuit*

9.5 Secondary circuit*

9.6 Down guy

H

72

(Continues)

*Identify by notation or schedule.

Symbols for Arrester, Lightning Arrester Gap

Arrester, Lightning Arrester (Electric Surge, etc.) Gap:

9.7 Head guy

9.8 Sidewalk guy

9.9 Service weather head*

10.2 Carbon block. Block, telephone protector.The sides of the rectangle are to beapproximately in the ratio of 1 to 2 and thespace between rectangles shal l beapproximately equal to the width of a rectangle

10.1 General.

10.3 Electrolytic or aluminum cell. This symbol isnot composed of arrowheads.

10.4 Horn gap.

10.5 Protective gap. These triangles shan’t befilled.

73

(Continues)

Meter Instrument:Symbols for Meter Instruments.A Ammeter IECAH Ampere-hourCMA Contact-making (or -breaking) ammeterCMC Contact-making (or -breaking) clockCMV Contact-making (or -breaking) voltmeterCRO Oscilloscope or cathode-ray oscillographDB DB (decibel) meter

10.5 Protective gap. These trianglesshan’t be filled.

10.6 Sphere gap.

10.7 Valve or film element.

10.8 Multi-gap, general.

10.9 Application: gap plus valve plusground, 2 pole.

74

(continued)DBM DBM (decibels referred to 1 milliwatt) meterDM Demand meterDTR Demand-totalizing relayF Frequency meterG GalvanometerGD Ground detectorI IndicatingINT Integrating_Aor UA MicroammeterMA MilliammeterNM Noise meterOHM OhmmeterOP Oil pressureOSCG Oscillograph stringPH PhasemeterPI Position indicatorPF Power factorRD Recording demand meterREC RecordingRF Reaction factorSY SynchroscopeTLM TelemeterT Temperature meterTHC Thermal converterTT Total timeV VoltmeterVA Volt-ammeterVAR VarmeterVARH Varhour meterVI Volume indicator; meter, audio levelVU Standard volume indicator; meter, audio levelW WattmeterWH Watthour meter

75

Remote Control Stations for Motors or Other Equipment:Symbols for Remote Control Stations for Motors or Other Equipment.

11.1 Pushbutton station

11.2 Float switch—mechanical

11.3 Limit switch—mechanical

11.4 Pneumatic switch — mechanical

11.5 Electric eye—beam source

11.6 Electric eye—relay

11.7 Thermostat

F

L

P

T

76

CHAPTER FOURPRINTS AND DRAWINGS.

4.1 Introduction to Print Reading

The Title Block

FirstArea of the Title Block

SecondArea of the Title Block

The ability to read and understand information contained on drawings is essentialto perform most engineering-related jobs. Engineering drawings are means ofcommunicating detailed and accurate information on how to fabricate, assemble,troubleshoot, repair, and operate a piece of equipment or a system. To understandhow to "read" a drawing it is necessary to be familiar with the standard conventions,rules, and basic symbols used on the various types of drawings. A genericengineering drawing can be divided into the following five major areas or parts.1. Title block2. Grid system3. Revision block4. Notes and legends5. Engineering drawing (graphic portion)

The title block of a drawing, usually located on the bottom or lower right handcorner, contains all the information necessary to identify the drawing and to verifyits validity.Atitle block is divided into several areas as illustrated by Figure 1.

The first area of the title block contains the drawing title, the drawing number, andlists the location, the site, or the vendor. The drawing title and the drawing numberare used for identification and filing purposes. Usually the number is unique to thedrawing and is comprised of a code that contains information about the drawingsuch as the site, system, and type of drawing. The drawing number may alsocontain information such as the sheet number, if the drawing is part of a series, or itmay contain the revision level. Drawings are usually filed by their drawing numberbecause the drawing title may be common to several prints or series of prints.

The second area of the title block contains the signatures and approval dates,which provide information as to when and by whom the component/system wasdesigned and when and by whom the drawing was drafted and verified for finalapproval. This information can be invaluable in locating further data on thesystem/component design or operation. These names can also help in theresolution of a discrepancy between the drawing and another source ofinformation.

ELECTRICAL

77

ThirdArea of the Title Block

Drawing Scale:

1" = 1"

3/8" = 1'

1/2" = 1'

Grid System:

The third area of the title block is the reference block. The reference block lists otherdrawings that are related to the system/component, or it can list all the otherdrawings that are cross-referenced on the drawing, depending on the site's orvendor's conventions. The reference block can be extremely helpful in tracingdown additional information on the system or component.

Drawings can be classified as either with scale or those not drawnto scale. Drawings without a scale usually are intended to present only functionalinformation about the component or system. Drawings with scale allow the figuresto be rendered accurately and precisely, it also allow components and systems thatare too large to be drawn full size to be drawn in a more convenient and easy to readsize. A very small component can be scaled up, or enlarged, so that its details canbe seen when drawn on paper. Scale drawings usually present the informationused to fabricate or construct a component or system. If a drawing is drawn toscale, it can be used to obtain information such as physical dimensions, tolerances,and materials that allows the fabrication or construction of the component orsystem. The scale of a drawing is usually presented as a ratio and is read asillustrated in the following examples:

Read as 1 inch (on the drawing) equals 1 inch (on the actual component orsystem). This can also be stated as FULL SIZE in the scale block of the drawing.The measured distance on the drawing is the actual distance or size of thecomponent.

Read as 3/8 inch (on the drawing) equals 1 foot (on the actual componentor system). This is called 3/8 scale. For example, if a component part measures 6/8inch on the drawing, the actual component measures 2 feet.

Read as 1/2 inch (on the drawing) equals 1 foot (on the actual componentor system). This is called 1/2 scale. For example, if a component part measures 1-1/2 inches on the drawing the actual component measures 3 feet.

To help locate a specific point on a referenced print, most drawings,especially Piping and Instrument Drawings (P&ID) and electrical schematicdrawings, have a grid system. The grid can consist of letters, numbers, or both thatrun horizontally and vertically around the drawing. Like a city map, the drawing isdivided into smaller blocks, each having a unique two letter or number identifier. Forexample, when a pipe is continued from one drawing to another, not only is thesecond drawing referenced on the first drawing, but so are the grid coordinateslocating the continued pipe. Therefore the search for the pipe contained in the blockis much easier than searching the whole drawing.

78

Revision Block: When a drawing is first issued, it is called revision zero, and therevision block is empty. As each revision is made to the drawing, an entry is placedin the revision block. This entry will provide the revision number, a title or summaryof the revision, and the date of the revision. The revision number may also appearat the end of the drawing number or in its own separate block. As the component orsystem is modified, and the drawing is updated to reflect the changes, the revisionnumber is increased by one, and the revision number in the revision block ischanged to indicate the new revision number.

There are two methods of indicating where a revision has changed in adrawing, the first is the cloud method where each change is enclosed by a hand-drawn cloud shape and the second method involves placing a circle (or triangle orother shape) with the revision number next to each effected portion of the drawing.The cloud method indicates changes from the most recent revision only, whereasthe second method indicates all revisions to the drawing because all of the previousrevision circles remain on the drawing.

Drawings are comprised of symbols and lines that representcomponents or systems. Although a majority of the symbols and lines are self-explanatory or standard a few unique symbols and conventions must be explainedfor each drawing. The notes and legends section of a drawing lists and explains anyspecial symbols and conventions used on the drawing. Also listed in the notessection is any information the designer or draftsman felt was necessary to correctlyuse or understand the drawing. Because of the importance of understanding all ofthe symbols and conventions used on a drawing, the notes and legend sectionmust be reviewed before reading a drawing.

The five engineering drawing categories are:P&IDsElectrical single lines and schematicsElectronic diagrams and schematicsLogic diagrams and printsFabrication, construction, and architectural drawings

are usually designed to present functional information about a system orcomponent. Examples are piping layout, flowpaths, pumps, valves, instruments,signal modifiers, and controllers,

Changes :

Notes and Legend:

4.2 Types of Drawings and Drawing Formats.

P&IDs

P&IDs do not have a drawing scale and presentonly the relationship or sequence between components

79

These drawings only present information on how a system functions, not the actualphysical relationships. Because P&IDs provide the most concise format for how asystem should function, they are used extensively in the operation, repair, andmodification of the plant. One of the main purposes of a P&ID is to providef u n c t i o n a li n f o r m a t i o n a b o u t h o w i n s t r u m e n t a t i o n i n a s y s t e m o rp iece of equipment in ter faces wi th the system or p iece ofequipment.

are designed to present functionalinformation about the electrical design of a system or component. Examples oftypical single lines drawings that are related to the system/component, or it can listall the other drawings motor start circuits, and breaker circuits are site or buildingpower distribution, system power distribution, and motor control centers. Electricalschematics provide a more detailed level of information about an electrical systemor component than the single lines. Electrical schematic drawings presentinformation such as the individual relays, relay contacts, fuses, motors, lights, andinstrument sensors. Examples of typical schematics are valve actuating circuit

are designed to present information aboutthe individual components (resistors, transistors, and capacitors) used in a circuit.These drawings are usually used by circuit designers and electronics repairpersonnel.

can be used to depict several types of information.The most common use is to provide a simplified functional representation of anelectrical circuit, For example, it is easier and faster to figure out how a valvefunctions and responds to various inputs signals by representing a valve circuitusing logic symbols, than by using the electrical schematic with its complex relaysand contacts. These drawings do not replace schematics, but they are easier touse for certain applications.

are designed to presentthe detailed information required to construct or fabricate a part, system, orstructure. These three types of drawings differ only in their application as opposedto any real differences in the drawings themselves and are usually drawn to scale..Fabrication drawings are usually found in machine shops and provide thenecessary detailed information for a craftsman to fabricate a part. Constructiondrawings, commonly referred to as "blueprint" drawings, present the detailed

Electrical single lines and schematics

Electronic diagrams and schematics

Logic diagrams and prints

Fabrication, construction, and architectural drawings

80

information required to assemble a structure on site. Architectural drawingspresent information about the conceptual design of the building or structure.Examples are house plans, building elevations (outside view of each side of astructure), equipment installation drawings, foundation drawings, and equipmentassembly drawings.

P&IDs, fabrication, construction, and architectural drawings can be presentedusing one of several different formats. Each format provides specific informationabout a component or system. The standard formats are single line, pictorial ordouble line, and cutaway.

represents all piping, regardless of size, as single linecommonly used in P&IDs .All system equipment is represented by simple standardsymbols. single lines allow the system's equipment and instrumentationrelationships to be clearly understood by the reader.

present the same type information as a singleline, but the equipment is represented as if it had been photographed. This format israrely used since it requires much more effort to produce than a single line drawingand does not present any more information as to how the system functions. Used inadvertising and training materials.

are a special application of pictorial drawings that are commonin the engineering field , an assembly drawing is a pictorial view of the object with allthe components shown as they go together. This type pictorial is usually found invendor manuals and is used for parts identification and general information relativeto the assembly of the component

is another special type of pictorial drawing. In a cutaway, as thename implies, the component or system has a portion cut away to reveal theinternal parts of the component or system. Figure 15 is an illustration of a cutaway.This type of drawing is extremely helpful in the maintenance and training areaswhere the way internal parts are assembled is important.

To read and interpret electrical prints, you need to recognize the graphic symbolsfor electrical diagrams and the electrical wiring equipment symbols as shown in

Symbols for Electrical and Electronic Diagrams and Electrical Wiring

4.3 Drawing Format

The single line format

Pictorial or double line formats

Assembly drawing

Cutaway drawing

4.4 Electrical WiringAnd Schematic Diagram Reading

Graphic

81

Equipment Symbols. In addition, you must also be familiar with the system ofnumbering electrical units and marking electrical cables as described in thefollowing paragraphs. , you need to understand the symbolsfor various electronic components. It's also helpful to know how to analyze thecircuits to determine their function. Schematics often assign labels to parts basedon their type and arbitrary ordering on the schematic. For example, R stands forresistor; on a schematic with numerous resistors, it might show the first resistor onthe left-hand side of the schematic labeled as R1.

To read a schematic

To read a wiring diagram

4.5 How to Read Electrical Diagrams

, youneed to understand the types of packages available for different parts. For large-scale wiring diagrams, such as those for a house, the resources on installingelectrical components provide symbols. For wiring diagrams for a small circuit,such as the one found in a cell phone, a parts list provides the information needed tolook up each component's packaging on its manufacturer's website. In some cases,the schematic symbol and the wiring diagram symbol are the same. Many wiringdiagrams also have a key that provides important information such as wire gaugeand colors. Wiring diagrams for circuits use the same labels as the schematic.Using the same example as above, the wiring diagram includes R1 from theschematic but, instead of being on the far left, it is depicted in the middle, which is itsactual location on the circuit board.

Electrical diagrams range from the very simple to the very complicated, but they allare based on the same elementary principles. To learn how to read them, it isnecessary to have a basic understanding of the parts used in circuits, including theirsymbols, what they are used for, and how they are placed inside a circuit.1. Identify the most common symbols for electrical components. Resistors,capacitors, inductors, transistors, op-amps and diodes all have different symbols.Wires are represented as straight lines. They are treated as perfect conductors, soare considered to have zero resistance.2. Study the rules that are used to wire these components together. These arefound in basic physics and electronics texts. They may also be found on the back ofthe component packages and on some data sheets.For example, the rules for connecting resistors are different from those ofcapacitors or inductors. An extremely important rule for components is that theymay be wired in series or parallel. Points connected by the same wire are at thesame potential and are electrically equivalent.3. Memorize the symbols for voltage sources. A voltage source, such as a powersupply or battery, may be symbolized in more than one way on a diagram. A directcurrent may come from a power supply or battery, while an alternating current

82

comes from a power supply. A voltage source is polarized, which means that theway it is placed into a diagram is important. The anode is the + (plus) or positiveside, and the cathode is the -- (minus) or negative side. The negative side is alsoreferred to as the ground.4. Recognize the difference between polarized and non-polarized components.Like voltage sources, some components are also polarized. The way they areplaced into the circuit with respect to the voltage source is important, while othersare independent of their circuit direction. Some capacitors are polarized, whileresistors are not.5. Identify the outlets. Outlets usually are small, unshaded circles,with one line leading from the circle to the wall. If there are two lines, it indicatesmultiple outlets. Three lines mean an appliance outlet for larger items like dryer andranges. 5. Learn the most common fundamental circuit combinations. These arecertain electrical components that are always wired the same way using the sameparts. Their role is to form mini-circuits that are used to perform certain tasks for alarger circuit. They may be viewed as building blocks. Examples of such are voltagedividers, diode clamping circuits and filters. Once you have mastered the basicanalog circuits, you may proceed to logic circuits.

Residential electrical diagrams vary according to what the diagram is for and who iscompiling the information. These kinds of diagrams are helpful in aidinghomeowners in not only wiring their own home but locating the existing wires withinthe completed structure. Diagrams that are in color, not just black and white, may bemore helpful the novice reader however everyone should be aware that thesymbols used on their diagram may be different from others for currently there is no"official code" regarding the use of symbols on blueprints or schematics forresidential drawings.Instructions:1. Obtain a key or reference chart for use when identifying the wiring symbols. Mostwiring diagrams will have one included on the printout. If one is not included,libraries usually have a good selection of reference material regarding electricalsymbols. Some dictionaries, such as Webster's, have the symbols included in theback.2.Acquire a copy of the wiring diagram for your home. If it is being built, or is a newerhome, try getting one from the contractor or architect. For older homes, the localcode enforcement office may have a copy in larger municipalities however for someprojects the diagram may not be available except through the previous homeowneror builder.3. Locate the main panel on the diagram. This panel is where the main power line

4.6 How to Read a Residential Wiring Diagram

83

enters the residence and is typically indicated by a diagonally striped or shadedrectangle shape located on/in a wall in a utility room, garage or basement. On somedrawings, there may be an angled line extending from the panel icon as to indicatean open door.4. Recognize the switches. Switch symbols usually resemble an "S," with or withouta single or multiple lines running vertically through it; however it may have a smallnumber beside it in lieu of the lines. The number, or number of lines, usuallyindicates the type of switch that will be installed along with how many. A letter "S"beside the outlet means it is "switched" and can be turned off and on with a switch. Ifthere is a number next to the circle, it means there will be more than one outletinstalled. Special purpose outlets will have a triangle inside the circle. And flooroutlets are indicated by a dot inside a circle.6. Find the fixtures. Fixtures are things such as lights, fans, exhaust vents overstoves, etc. Lights are usually drawn as a circle with four lines extending out fromthe sides. Recessed lights may have a square shape around them. Vanity, track,and bar lights may be a series of small circles attached to a rectangle. Spotlightsmay be two side-by-side triangles. Fluorescent lights are usually a long rectangleshape.7. Identify the special symbols. Special symbols indicate things such asthermostats (a circle with a "T"), smoke detectors (a circle with an "SD"), phones (alone triangle with line to wall), doorbells (a square with a circle within), andtelevisions (a rectangle with the letter "TV"). Ceiling fans look like small, four-bladed fans. And electrified exhaust vents or vents are usually square with an "X"shape inside.

Circuit wiring diagrams are important tools in electronics. They are representationsof circuits, and so allow users to replicate them without needing models or having tobe physically present. Their form makes it an easy way to transmit importantinformation.Circuit wiring diagrams are different from schematics in that they emphasizepictures instead of symbols. They show the positions of the wires, and how thedevices are physically arranged next to each other. They are useful introubleshooting circuits that don't work properly. To learn to read circuit wiringdiagrams, it is necessary to learn some basic rules.

1. Memorize the colors most often used to distinguish the role of wires in circuits.The hot wires are normally colored red and black. Red is connected to the positiveside of a voltage source, while black is connected to the negative side. Green or

4.7 How to Read Circuit Wiring Diagrams

84

bare wire usually means neutral, which means it is connected to a point on a devicethat carries no current. There may be additional wires as well, and some diagramsmay use colors different from the ones stated. These will be clearly indicated.2. Study the different types of switches, including their purpose and operation.Switches are one of the most common types of devices shown in wiring diagrams.Popular ones include light dimmers, and three-way or four-way switches. Three-way switches let the user control electricity from two areas, such as controlling onelamp from two different floors. Four-way switches can control electricity from threeareas.3. Examine the different types of outlets, which are another very popular subject forwiring diagrams. Outlets for household use are usually made for 110 to 120 volts,and have ground connections. Dryers and other large household appliances mayrequire 240-volt outlets.4. Recognize the symbols and drawings used most often in circuit wiring diagrams.Colored lines are used to represent wires and their various roles. Lamps aresymbolized using light bulbs. Outlets and switches have drawings that clearly looklike them, though some may be shown as merely boxes or rectangles.

A wiring diagram or schematic visually represents the way that a circuit isconstructed. A typical automotive wiring diagram represents a single system ofyour vehicle. For instance a wiring diagram for your vehicle might represent theinterior lighting system. When you are having electrical issues with your car, it is auseful skill to know how to read these diagrams. Remember that the diagrams arenot literal drawings of the locations of electrical parts, but symbolize the parts andconnectionsInstructions:1. Obtain a sample wiring diagram representing a system of a vehicle. Try factoryrepair manuals, website, or your vehicle's owner's manual as a source for adiagram.2. Learn the symbols for the basic components on a wiring diagram; these are theswitch, resistor, ground point, and battery. Remember the standard variations thatexist for the battery (variable battery) symbol and the ground (case ground) symbol.3. Memorize what the advanced component symbols look like and what the labelsnear them stand for. They might be used to designate component positive andnegative terminals, component pin numbers, or component electrical or circuitvalues. Obtain a guide with a full listing of symbols if you come across a schematicwith something that is not labeled.

4.8 How to Read Car Wiring Diagrams

85

4. Learn how the wires and connections are drawn. Remember a dot symbolizesthat two wires are connected, while a wire with no dot symbolizes wires that crossphysically but are not connected. Note that the notations like "BRN/WHT" or "LTGRN" denote the colors of the wires themselves.

Automotive wiring has been standardized over the decades, and most cars willhave "color-coded" wiring for lighting, radio, ignition, and secondary systems. Thiscolor coding makes it easier for the layman to quickly repair most automobile wiringissues. You can learn to understand the wiring diagrams by following some basicprinciples.Understanding colors:1. Locate the source of the electrical problem, such as a damaged relay. Find thelocation of the issue shown in the diagram. The repair manual will providetroubleshooting steps to determine which electrical component is damaged ormalfunctioning.2.After locating the faulty part on the diagram, usually by labels or shape, the colorsof wire on the page should exactly match the wire colors in the vehicle. This willassist in tracing the wire back to it's power source, or on to the next electrical circuit.Symbols on the diagram could vary, but typically follow electrician standards.3. In rare cases, the diagram could be in black and white, or printed without colors.This is when the "path", or lines on the schematic become important. Sometimes,there may even be very small text next to each line, designating what color it is. Thiscan appear as "DRK GRN" for dark green, or "YEL/BLK" for a yellow wire with a thinblack stripe.Modern automotive wiring diagrams use electronics symbols to depict the differentcomponents in the vehicle. Each circuit has its own diagram, and the placement ofeach component in the diagram bears no resemblance to the location of thatcomponent in the vehicle. Despite their complexity, it is possible to read automotivewiring diagrams with a basic knowledge of electronics symbols.Instructions:1. Choose one circuit in your vehicle to examine. Typical circuits include the alarmcontrol, airbag, engine control, heater, horn, instrument panel, lighting, ignition,power windows, starter, transmission and windshield wipers.2. Examine the wires on the diagram indicated by straight lines on the diagram,referenced by the color of the wire in the vehicle or printed in that color. Where wirescross on the diagram, a dot represents a connection. Where there are no dots, thisrepresents wires that are not physically connected.3. Note the colors of the wires on the diagram. If the diagram is printed in color, the

4.9 How to ReadAutomotive Wiring

86

lines are usually the same color as the wire. For black and white diagrams, thecolor will appear in small print beneath the wire. A red wire is usually a 12-volt hotwire.Ablack wire is typically a ground wire.4. Identify the power supply on the diagram, generally placed at the top of the

diagram. A battery power cell would be represented by two wires with a spacebetween them, with two vertical lines terminating at each wire line. The tall verticalline is positive, and the small vertical line is negative. A direct current supply isillustrated by two wires and a space between them, with a "+" over the end of onewire and a "-" over the end of the other wire.5. Trace the wire on the diagram until you find the fuse. A fuse is depicted as a linefor the wire running through a long rectangle.6. Trace the wire from the fuse to the functioning device on the circuit. A motor isdepicted as an "M" inside a circle. An indicator light, such as a turn signal indicatoron the dashboard, is shown as an "X" inside a circle.7. Refer to the detailed notes that go with the wiring diagram of the circuit you arereading. This will give you a full understanding of the circuit and help you comparewhat you see on the diagram with what you see in the circuits of the vehicle.8. Compare the wiring diagram to the wires and electrical components on yourvehicle.

Here are some examples to deepen the readers understanding of print reading:Examples:

1. ReadingAWiring Diagram ForAppliance Repair

A wiring diagram is a drawing of the electrical circuit of whatever it is you areworking on. Often when working on appliances, it is necessary to read thesediagrams when there is an electrical problem with the appliance you are workingon. Knowing how to read a wiring diagram can save you from buying parts you don'tneed. Every appliance comes with a diagram hidden on it somewhere such asunder the bottom, in the control panel behind the storage drawer or taped to theback. It will be somewhere you will not find it unless you were looking for it. IIf youhave an electrical device that will not work, look at the diagram and find the device.Everything between the two main lines that the light is on can affect the light. Alsoyou should know that the main lines are marked L1, L2 and N. If a diagram has justL1 and N then the circuit is 110V, if the diagram has L1 and L2 then it is a 240 circuitand if it has L1, L2 and N it is a 110-220V circuit. Below is a picture of a few simpleladder-wiring diagrams to help in the explanation.

87

Figure 4.1. 110V Light Circuit

looking at figure 4.1 you should see that both lights run all the time because thereisn't a switch to control them or a fuse. Also note that both lights run off of 110Vbecause they are connected between the Land the N.

Figure 4.2. 110V Light Circuit With SwitchAnd Fuse

Light

Light

L n

Light

Switch

Fuse

L N

88

Figure 4.2 is a 110-220V circuit controlled by a switch; one of the lights is switchedcontrolled while the other is directly connected to the supply.Looking at figure 4.3, there is a light that runs off of 110V and is controlled by aswitch. There is a heater that runs off of 220V and is controlled by a switch and athermostat. There is a fuse that turns both the heater and the light off if it is blown.

Figure 4.3. 110 - 220V Circuit

Figure 4.4 is a simple dryer wiring diagram that shows examples of most of whatyou will see on many other wiring diagrams. Lets break it down and explain eachcomponent of the dryer and how it is controlled.The Motor: The motor is the most complicated part of this diagram. Notice that themotor coils are connected to an internal motor switch, which is only closed if themotor is running. This is why there is a start switch; the start switch temporarybypasses the motor switch to allow the motor to run. Once the motor starts, you nolonger need the start switch because the motor switch takes over so the start switchis only closed when you are pressing on it. There is also a timer switch and a doorswitch that have got to be closed in order for the motor to run. So when the timer ison, the door is closed and the start switch is pressed, the motor will start. It runs offof 110V.The heater:A timer switch, two thermostats and the motor switch control the heater.The motor switch will only close if the motor is running. One of the thermostats is forturning the heater on and off during normal operation. The other thermostat is forsafety and will turn the heater off if it overheats. The timer switch is on when thetimer is on and calling for heat. It runs off of 220V.

LightSwitchFuse

HeaterSwitch Thermostat

L1 N L1

89

Figure 4.4. Simple Dryer Circuit

someone comes and turns it on. This means that the timer turns off when it gets to apoint. It runs off of 110V.

The light: The light is on when the door is open so that you can see inside the drum.It runs off of 110V.The safety switch: The safety switch is a switch that cuts the entire dryer off if itoverheats.

Note that this is not an actual dryer wiring diagram, it is just a sample drawn to helpyou understand wiring diagrams.

The first thing that should be done upon receiving a set of plans for a building is toreview them, scanning each one to get an overview of the building. The electricalsystem, the air-conditioning and heating system, and the plumbing system for abuilding are very closely related. Design technicians and installation techniciansmust coordinate the systems of all trade areas to have a well-designed and smoothinstallation on the job. On larger buildings, the electrical plans usually contain plansfor lighting, power distribution (showing receptacles and special connections),

The timer: The timer motor runs until the timer switch turns it off and it stays off until

4.10 Reading and Interpreting Electrical Plans.

Safety Thermostat

Timer SwitchTimer Motor

Start Switch

Timer Switch

Timer Switch

Light

Door Switch

Thermostat ThermostatHeater

Motor Switches

Motor

L1 L2N

90

panel schedules, and other schedules and details pertaining to the electricalsystem.

The lighting plan and the power distribution plan are consolidated on the same floorplan an illustration shown in figure 4.5. Lighting fixtures are shown with rectanglesfor fluorescent fixtures and circles for other types of fixtures. Each lighting fixture isidentified by a letter of the alphabet. These letters are shown on the lighting fixtureschedule on the plan. The power distribution is not shown on the plan. Theelectrical receptacles use the standard symbol. The hash marks on the circuit linesindicate the number of conductors (wires) required. All of the circuits are indexed(numbered), and these numbers indicate the number of the circuit breaker in thedistribution panel. A schedule for any Panel is always shown on the plan with eachcircuit numbered. The service to the panel is shown with a separate detail. Themain circuit breaker is located inside the Panel. The exact location of the wiringand conduit is left to the installing technician. On each wire are hash marksindicating how many wires are required with the circuit. The arrowhead at the end ofa wiring symbol indicates that the conduit should to be extended to the panel. Thesmall number that is sometime located at the arrowhead gives the number of thecircuit breaker to which the wiring is to be connected. Additional information that isalways rendered in the plan includes, A lighting fixture schedule on the plandescribing the lighting fixtures that are to be used is always rendered on the planalso. Each fixture shown on the floor plan has a letter that corresponds to the fixtureschedule. A symbol schedule identifies the symbols used on the plan. The powerriser diagram is also shown in the lower right-hand corner. A general note is alsoshown on the plan giving instructions to the contractor.A note at the top right corner of the plan restricts the use of the plans. Electrical

work shown on the site plan can be the first sheet of the electrical section. Theelectrical section also includes the following:

—shows electrical equipment (panel boards,switches, electrical outlets, etc.) required for the basement, located in the crawlspace, or located under a slab on grade.

—show the electrical equipment required for each floor, includingreceptacles, lighting fixtures, and necessary electrical connections to equipmentfurnished by other contractors.

—electrical wiring, equipment, and electrical connections to equipmenton the roof are shown on the electrical roof plan.

—these are detailed drawings showing how theelectrical equipment is installed. Special instructions and information are relayed to

Reading The Electrical Plans

Foundation/Basement Plan

Floor Plans

Roof Plan

Elevations, Sections, and Details

91

Figure 4.5. Electrical Plan.

LEGEND

CEILING MOUNTED FIXTURE

RECESSED FIXTURE

WALL MOUNTED FIXTURE

WALL MOUNTED FIXTURE WITHPULLCHAIN

DUPLEX OUTLET

DUPLEX OUTLET (220)

EXHAUST FAN

FLUORESCENT FIXTURE

ELECTRICAL PANEL

SWITCH

3 WAY SWITCH

PANEL

220

S

S3

92

the electrical worker through these drawings.—contains schedules for the electrical devices, including the

following:A. Lighting fixture scheduleB. Panel board scheduleC. Conduit and raceway schedule

Interpreting plans is an important part of the electrical trade. Floor plans can beused to show the location of electrical installations. It is important that information iscorrectly understood to enable the planning, construction and alteration ofelectrical installations.

Calculating Dimensions:The understanding of plans is necessary to establish the exact positions ofelectrical installations. Positions of electrical installations are dictated by roomdimensions, the location of appliances and the wiring rules. Positions aredetermined by allowing for, the dimensions of appliances and fittings.Dimensions:From figure 4.5,The room Length 3 meters (300 cm)The shower base 90 cmThe wash basin unit 90 cmDistance of wash basin unit from western wall xcm = Unknown

= Room Length - ( Wash Basin Unit + Shower base)x = 300 - (90 + 90)x = 120 cm

Most plans are drawn to a scale. For ease of representation, large dimensionsare converted to smaller metric units. The principle of ratio is used to indicatethe scaleFor example;1:10001:1001: 50On a plan 1:100 might mean that 1 cm is equivalent to 100 cm (1 meter).On a map 1:10 might mean that 1 mm is equivalent to 10 kilometers.

Schedule Plan

4.11 Interpreting Plans

Scale:

93

Figure 4.6 Bathroom Floor Plan: Example 1

“X” Ba

thro

om

Flo

or P

lan

3000m

m

900m

m900m

m

Wash B

asin

Show

er

94

Figure 4.7: Example 2 The GPO in the Lounge Room is located on the southern wall.

Figure 4.8: Example 3 The Dining Room is east of the kitchen.

Lounge Room

Dining RoomKitchen

North

West East

South

95

Example 4

Figure 4.9 Floor Plan

96

Calculate the following dimensions and record the measurements in meters on theabove floor plan (figure 4.9). Use a ruler with centimeter markings to find themeasurement.a. The length of the interior southern wall of Bedroom 2?b. The length of the external northern wall of the house?c. The length of the interior eastern wall of the house?d. The length of the interior northern wall of the Laundry?e. The width of the Entrance?f. The length of the interior eastern wall of the Lounge.g. The length of the eastern wall of Bedroom 3.

An electrical plan is a detailed drawing of all outlets, lights, and switches in a house.The plan will show the location of the outside electrical service, inside panel, andany disconnects. Three way switches will be noted along with any switchedreceptacles. The location of all lights will be shown and it should note if there will beany specialty switching such as dimmers. Other items that should be shown on anelectrical plan are GFI receptacles, outside receptacles, dryer or stove outlets andany specialty receptacles such as for sight and hearing impaired. The overall planshould give a complete view of everything pertaining to electrical items in a house.The electrical plan should contain an electrical symbols list. This will show eachelectrical symbol and what it means.An electrical plan is a plan view similar to the floor plan in that all the walls, doors,and windows are shown along with the electrical symbols that describe service tothe house. It also includes what is known as a legend which defines what eachsymbol represents. There are several considerations that have to be made whendrawing an electrical plan for a house. They are as follows:

The electrical meter is always on the exterior of the home. This is the location wherepower enters the house into the circuit box. The circuit box is located no more thantwelve feet away from where the power enters the homes. From this locationelectricity is distributed to the individual rooms. The circuit box is usually located ina service area of a home like the utility room or kitchen. If the home has a basement,this is usually the preferred location for it to be placed.

Light fixtures are usually placed in the middle of a room to allow even lightingthroughout. Sometimes these are included in special fixtures like ceiling fans.

4.12 DrawingAn Electrical Plan

The Meter and Service Box

Light Fixtures, Light Switches, and Receptacles

97

When a fixture is placed in a large closet, it is usually mounted so that it is at leastthree feet from where the clothing is hung to insure against a fire from its heat.Exterior lighting should be waterproof in some way to eliminate the possibility ofelectrical short. The light switches almost always are mounted next to a roomentrance for convenience. When switching an exterior light, these are usuallylocated inside near the exterior lights location. Receptacles, also known as outletsare usually spaced every six feet in a room. This is to make sure that electricalcords do not have to be stretched far from the appliance they are powering. Sometimes a homeowner requests that the top half of a receptacle be controlled by a lightswitch to make turning off lamps simpler. Exterior receptacles and those inside thehouse within six feet of a water source like a sink are ground fault interrupt. This isto eliminate possible shock if shorted by water. All of these are one hundred andtwenty volt with a few exceptions and the amperage varies

These are required by code for fire safety. The must be located in each individualbedroom and also near each exit from the home. These are usually batterypowered so that even if the power is out, they will still function.

These are usually drawn using a arched dashed line showing which switch controlswhat light or receptacle. There are many more considerations like two twenty voltpower for appliances such as the stove or electrical clothes dryer. You may alsoplace special fixtures like phone jacks and cable tv connections on this plan.

Drawing accurate, detailed electrical floor plans is one of the essential steps inapplying for an electrical-wiring permit. Standard symbols indicate the location ofduplex outlets, special-purpose outlets, switches, wall-light outlets, ceiling-lightoutlets, and switches on electrical floor plans. ANSI (American National StandardInstitute) symbols are industry standards and recognized by the AHJ (AuthorityHaving Jurisdiction), electrical inspectors, and building department engineers whoissue electrical permits. The symbols are easy to remember but keep a copy ofthem nearby to avoid errors.

1. Draw a floor plan to scale. A scale of ¼ inch to the foot is a convenient scale towork with. Using that scale, most homes will fit on a sheet of 11-inch by 17-inchgraph paper.

2. Indicate the locations of all general-purpose duplex receptacles in rooms andhallways. Review NECArticle 210.52 Dwelling Unit Receptacle Outlets for more

Smoke Detectors

Wiring Connections

4.13 How to Draw an Electrical Floor Plan With Circuits

98

information. In summary, no point measured along the unbroken floor line can bemore then 6 feet from a receptacle outlet, keeping in mind that a duplex outletcounts as two outlets. Any wall space 2 feet in width or wider must have areceptacle outlet. Any hallway 10 feet or longer must have at least one receptacleoutlet. Place the first receptacle 6 feet from the first break in floor line, then place therest at 12-foot intervals. One duplex receptacle fulfills the rule for a span of 6 feet toeach side of its location.

3. Draw in the positions of all wall- and ceiling-light outlets.

4. Draw in the positions of all wall-mounted switches.

5. Show the position of all the special-purpose receptacles--those for an electricrange, clothes dryer, garbage disposal, dishwasher, trash compactor, refrigerator,and deep freezer, for example.

6. Lay out the position of the kitchen countertop small-appliance circuits so nospace 2 feet or more in width is without a receptacle outlet and every wall space 12inches or more in width has a receptacle outlet per NEC Article 210.52(C)(1).7.Indicate the position of the circuit-breaker panel on the drawing.

8. Use solid, curved lines to indicate branch-circuit wiring concealed in walls andceilings; broken lines with long and short dashes to indicate branch-circuit wiringconcealed in floors; and dotted lines to indicate branch-circuit wiring that'sexposed.

9. Use solid lines with solid arrowheads pointing toward the circuit-breaker panel toindicate the cable bringing power from the service panel to the first device on thatcircuit.

10. Use short slashes drawn across these lines to indicate the number of circuitconductors in each cable run.

Produce the electrical wiring diagram of the ground floor plan for figure 4.10 - 4.12with standard symbols showing the legend, fixture and sub-circuit materialschedule, power riser diagram, control panel and the notes. Calculate theamperage of the distribution board and predict the generator size for the loadrendered on this plan.

Exercise.

99

Figure 4.10 Ground Floor Plan

sitting room

dining

car-port/entrance

masters room

bedroom 1 bedroom 2sh/wc

bath/wc

bath/wc

foyer

storage

kitchen

lobby

ver.

202512001050600900120014251050

150

23259006006001125

3600

150

1200

150

30001200

150

3600

150

1650

150 150

9600

3075

1200

938

600

450

600

1313

1200

2625

150

44

63

16

50

15

00

40

50

150

60

0

13050

23251200975750

325

3004450300

325

45018001950

150

4200

150

750

150

5550

150

4050

15015150

150

1650

2400

600

900

900

1500

900

750

3150

150

150

165

0

150

180

0120

0

150

450

0

150

315

0

150

1800

4500

1200

150

1800

3150

15

0

4500

150

3000

330

0150

150

0

15

0

315

0

15

0

450

0

195

0150

0315

0180

0255

0

4050

150

1500

1500

150

3600

150

1200

150

223

2096

681

825 2

25

3750

1650 150 3600 1050 150 3000 600 600 3600

5400 30001800 600

150150

2250

d1

d1

d2

d2

d2d2d2

d2

d3d3

d3

d3

d3

d3

42009005400

w1

w1

w2

w2

w2

w2w2

w3

w3

w3

w3

w4

w4

w4

w4

w4

w4

w3

w4

Scale: 1:100

ground floor01

1200

900

4950

3001800475120016251501350

5550

7950

3300

S01

S01

wc

600

450

900

100

Figure 4.11

entrybedroom 1

bedroom 2dining lounge

wc

wc/sh

kitchen storever.

101

Figure 4.12

lobby

1

lounge

entrance

bedroom 2

kitchen

dining

store

sh/wcbedroom 1

ver.

master bdrm

bath/wc

wc

sh/wc

F

102

CHAPTER FIVE

A breadboard is used to make up for testing or to try out anidea. No soldering is required so it is easy to change connections and replacecomponents. Parts will not be damaged so they will be available to re-useafterwards. Almost all the Electronics circuits and projects started life on abreadboard to check that the circuit worked as intended.

temporary circuits

ELECTRONIC COMPONENTS LAYOUTAND DRAWING

5.1 Introduction to Circuit Boards

Breadboard

Stripboard

Printed circuit boards

5.2 Bread Boards and Uses.

Circuit boards are used for constructing prototype and permanent electroniccircuits. They include the following:

used for temporary or prototype circuit construction where nosoldering is required. It provides a way of making a temporary circuit, for testingpurposes or to try out an idea. No soldering is required and all the components canbe re-used afterwards. It is easy to change connections and replace components.Almost all the Electronics Club projects started life on a breadboard to check thatthe circuit worked as intended.

has parallel strips of copper track on one side. The strips are 0.1"(2.54mm) apart and there are holes every 0.1" (2.54mm). Stripboard requires nospecial preparation other than cutting to size. It can be cut with a junior hacksaw, orsimply snap it along the lines of holes by putting it over the edge of a bench or tableand pushing hard.

have copper tracks connecting the holes where thecomponents are placed. They are designed specially for each circuit and makeconstruction very easy. However, producing the PCB requires special equipmentso this method is not recommended if you are a beginner unless the PCB isprovided for you.

Figure 5.1 Bread Board

103

Figure 5.1 shows a typical small breadboard which is suitable for building simplecircuits with one or two ICs (chips).

Breadboards have many tiny sockets (called'holes') arranged on a 0.1" grid. The leads of most components can be pushedstraight into the holes. ICs are inserted across the central gap with their notch or dotto the left. Wire links can be made with single-core plastic-coated wire of 0.6mmdiameter (the standard size) see figure 5.2. Stranded wire is not suitable because itwill crumple when pushed into a hole and it may damage the board if strands breakoff.

Figure 5.2 Physical connections on a bread board

From figure 5.3 the top and bottom rows are linked all the way across.The power supply is connected to these rows, + at the top and 0V (zero volts) at thebottom. I suggest using the upper row of the bottom pair for 0V, then you can usethe lower row for the negative supply with circuits requiring a dual supply (e.g. +9V,0V, -9V). The other holes are linked in blocks of 5 with no link across thecenter. Notice how there are separate blocks of connections to each pin of ICs.

On larger breadboards there may be a break halfway alongthe top and bottom power supply rows. It is a good idea to link across the gap beforeyou start to build a circuit, otherwise you may forget and part of your circuit will haveno power!

Connections on Breadboard:

Large Breadboards:

horizontally

vertically

104

Figure 5.3 Connection of Bread board holes.5.3. Converting a circuit diagram to a breadboard layoutConverting a circuit diagram to a breadboard layout is not straightforward becausethe arrangement of components on breadboard will look quite different from thecircuit diagram. When putting parts on breadboard you must concentrate on theirconnections not their positions on the circuit diagram. The IC (chip) is a goodstarting point so place it in the center of the breadboard and work round it pin by pin,putting in all the connections and components for each pin in turn. An example isbuilding a 555 timer circuit on breadboard shown in figure 5.4. We Begin bycarefully inserting the 555 IC in the center of the breadboard with its notch or dot tothe left. Then deal with each pin of the 555:Pin 1: Connect a wire (black) to 0V.Pin 2: Connect the 10k resistor to +9V.Connect a push switch to 0V (you will need to solder leads onto the switch)Pin 3: Connect the 470 resistor to an used block of 5 holes, then Connect anLED (any colour) from that block to 0V (short lead to 0V).Pin 4: Connect a wire (red) to +9V.Pin 5: Connect the 0.01 F capacitor to 0V.Pin 6: Connect the 100 F capacitor to 0V (+ lead to pin 6). Connect a wire(blue) to Pin 7: Connect 47k resistor to +9V.Check: there should be a wire already connected to pin 6.Pin 8: Connect a wire (red) to +9V.

μμ

105

Figure 5.4 Timer circuit on bread board

• Check all the connections carefully.• Check that parts are the correct way round (LED and 100 F capacitor).• (unless they connect to the same block).• Connect the breadboard to a 9V supply and press the push switch to test thecircuit.

Strip board has parallel strips of copper track on one side. The tracks are 0.1"(2.54mm) apart and there are holes every 0.1" (2.54mm). Strip board is used tomake up permanent, soldered circuits. It is ideal for small circuits with one or twoICs (chips) but with the large number of holes it is very easy to connect acomponent in the wrong place. For large, complex circuits it is usually best to use aprinted circuit board (PCB) if you can buy or make one. Strip board requires nospecial preparation other than cutting to size. It can be cut with a junior hacksaw, orsimply snap it along the lines of holes by putting it over the edge of a bench or tableand pushing hard, but take care because this needs a fairly large force and theedges will be rough. You may need to use a large pair of pliers to nibble away anyjagged parts. Avoid handling strip board that you are not planning to useimmediately because sweat from your hands will corrode the copper tracks and thiswill make soldering difficult. If the copper looks dull, or you can clearly see fingermarks, clean the tracks with fine emery paper, a PCB rubber or a dry kitchen scrub

μCheck that no leads are touching

5.4. Strip Boards

9VPowerSupply

106

before you start soldering. Figure 5.5 shows a typical small strip board that iscommonly used for simple circuits.

Components are placed on the non-copper side, then the strip board is turned overto solder the component leads to the copper tracks. Strip board layouts are shownfrom the component side, so the tracks are out of sight under the board. Layoutsare normally shown with the tracks running across the diagram.Placing components on strip board requires care. The large number of holesmeans it is very easy to make a mistake! For most small circuits the best method isto very carefully place the IC holder(s) in the correct position and solder in place.Then you can position all the other components relative to the IC holder(s).

Converting a circuit diagram to a strip board layout is not straightforward becausethe arrangement of components is quite different. Concentrate on the connectionsbetween components, not their positions on the circuit diagram. Collect all the partsyou will be using in the circuit so you can use a piece of strip board to work out theminimum space they require. For some components (such as IC holders) thespace required is fixed, but for others you can increase the space to obtain a betterlayout. space required is fixed, but for others you can increase the space to obtain abetter layout. For example most resistors require at least 3 hole-spacings if theyare to lie flat on the board, but they can easily span across a greater distance. If

horizontally

5.6. Planning a strip board layout

Figure 5.5 Small strip board.

5.5. Placing Components on Strip board.

107

necessary resistors can be mounted vertically between adjacent tracks (0.1"spacing) as shown in the diagram. This arrangement can help to produce a simplerlayout but the tracks are more likely to be damaged if the resistor is knocked. If youare designing a strip board layout for a serious long-term purpose it is best to mountall resistors horizontally. Plan the layout with a pencil and paper (or on computer ifyou have suitable software) and check your plan very carefully against the circuitdiagram before you attempt to solder any part of the circuit. The planning processis explained using figure 5.6. The circuit diagram is the starting point for any stripboard layout, even if you have already built a trial circuit on breadboard.

Figure 5.6. Astable Circuit Diagram

Place the IC holder near the center of your planning sheet with pin 1 at the top left(as in the diagram). You may find it helpful to number the pins.2. Mark breaks in each track under the IC holder with a cross (X). The breaksprevent opposite pins of the IC being connected together. The track beside eachpin of the IC is connected to that pin, the diagram shows this for pins 3 and 6.3. Mark the power supply tracks +Vs and 0V, choose tracks which are 2 or 3 spacesabove and below the IC holder as shown in the diagram.4. Now add the wire links. Draw a 'blob' diagram at each end of a link. The links arevertical because the strip board tracks make the horizontal connections. Tinnedcopper wire (with no insulation) can be used for these links unless there is a risk ofthem touching other wires (in which case use single core insulated wire). Workbund the IC pin-by-pin from pin 1.

1.

R1

R2

C1

R3

Vs

0V

555timer

2

6

78 4

3

1

+

108

Draw all the (+Vs and 0V). The diagram showspin 1 connected to 0V and pins 4 and 8 connected to +Vs.Draw any links required of the IC. There are nonein the example, but these links are straightforward to add.

require more thought. If the pins happento

direct links to the supply tracks

between pins on the same side

Links to pins on the other side of the ICbe opposite one another you can erase the track break (X) between them. Otherwise

the pins can be linked by connecting both of them to an unused track above or belowthe IC. The diagram shows pins 2 and 6 linked in this way. Another method is to linkthem with insulated wire bent around the IC

Layout step 1

Layout step 2

The four tracks must bebroken under the chipholder; marked with a cross x

this track if for + Vs

this track if for 0 Vs

this track is for + Vs

this track is for 0 Vs

R3

R1

R2

C1

LED555

109

Layout step 3

Layout step 4

5. Add components which will be mounted on the strip board such as resistors,capacitors and diodes. Make sure you allow for their size which determines theminimum number of holes, and sometimes the maximum as well. This is usually themost difficult stage of planning a layout so expect to change your plan severaltimes! Remember to label the components, otherwise it will become confusingonce there are several on the plan. connections which do not involve the IC aremade using an unused track.

this track is for + Vs

this track is for 0 Vs

R3

R1

R2

C1

LED555 red wire

to + Vs

black wireto OV

this track is for + Vs

this track is for 0 Vs

R3

R1

R2

C1

LED555

red wireto + Vs

black wireto OV

110

An alternative arrangements using the links you have already made. TtheLED needs to connect to 0V but it is a long stretch to the 0V track. It is easier toconnect the LED to the same track as pin 1 of the IC because that track is alreadyconnected to 0V by a wire link. Resistor R2 needs to connect from pin 7 to pin 6 andit could do this directly by mounting it vertically. However, it has been connectedfrom pin 7 to the track used to link pins 2 and 6, the extra space this gives allows R2to lie horizontally on the board.6. Add wires to components which will be off the strip board such as switches.These should normally be on the left and right at the edges of the board. Start byadding the battery clip or power supply leads to the +Vs and 0V tracks. Connectionsfor the other off-board components are usually easy because you do not need toallow for their size, just draw wires to the correct tracks.7. Check your plan very carefully by checking every connection shown on the circuitdiagram. A good way to do this is to work round the IC pin-by-pin. Check all theconnections and components connected to pin 1, then move on to pin 2, and so on.8. Look for ways to improve your plan. For example it may be possible to eliminatean unused track by moving a supply track nearer to the IC - but make sure there isstill sufficient space for the components. It may also be possible to move links andcomponents closer to the IC horizontally to make the area of board required a littlesmaller. Unused tracks above and below the IC have been eliminated in theexample. This affected two components, resistor R1 and capacitor C1, but both willstill fit in the reduced space.

Layout step 5

9. Finally, check your plan again and make a neat copy fully labeled with all thecomponent references or values. Work out the size of strip board required. Noticethat an extra hole has been allowed on the left and right to avoid soldering at the end

R3

R1

R2

C1

LED555

red wireto + Vs

black wireto OV

8 tracks (strips) x 20 holes

111

of a track. Joints made at the end of a track are likely to break because the smallpiece of track beyond the last hole easily breaks away from the board. The processexplained above give the outlines and steps to follow when developing the outlineof a given electronic circuit. Apart from the small strip board here are some otherboards used in electronic circuit construction and fabrication.

112

5.7. Reading Electronic Prints, Diagrams and SchematicsTo properly read prints and schematics, we must identify the condition of thecomponents shown and also follow the events that occur as the circuit functions.Electronic schematics are more difficult to read than electrical schematics,especially when solid state devices are used. Knowledge of the workings ofthese devices is necessary to determine current flow. The first observation indealing with a detailed electronic schematic is the source and polarity of power.Generally, power will be shown one of two ways, either as an input transformer, oras a numerical value. When power is supplied by a transformer, polaritymarks will aid in determining current flow. In this convention, dots on the primaryand secondary indicate current flow into the primary and out of the secondary at agiven instant of time. Figure 5.7 shows a circuit schematic showing power supply

connections +15.0v and -15.0v.

Figure 5.7 Schematic Showing Power Supply Connections

In any circuit, a ground must be established tocreate a complete current path.

R10 +15.0V

150�RB1.5K

RB1.5K

Cr1MZ8.2

CRSIN277

CRBIN277C1

50 f�

+ _

R1100�Q1

2N479AQ2

2N179

R4150�

INPUT

R2250 POT�

CR2 IN1530A

R6 150�

CR4MZ12

RS77�

R7177� R3

R114.7K

R12330�

500 POT�

CR3IN1530A

R133.3�

CRBMZ3.9

R15300�

R141.5K

CR7IN157

RELAYK1

042N672

032N396

113

Ground is usually depicted by the use of the ground symbol that was shownpreviously. The direction of current flow can be determined by observing thepolarity of the power supplies. When polarities are shown, current flow can beestablished and ground may not always be shown. With the power sources locatedand the ground point established, operation of the devices can be determined. Themost common semiconductor devices are the transistor and the diode. They aremade from materials like silicone and germanium, and have electricalproperties intermediate between conductors and insulators. The semiconductorwill be one of two varieties, the PNP or NPN. The designation indicates the directionthe electrons move through the device. Even though transistors contain multiplejunctions of p- or n-type material, current flow is generally in the samedirection. Using conventional current flow (i.e. from + to -), current will travel

Figure 5.8. (a) conducting, (b) non conducting transistors.

(a)

(b)

INPUT

POWER

CURRENT FLOW

EMITTER

BASEJUNCTION

INPUT

POWER

NO CURRENT FLOW

EMITTER

BASEJUNCTION

114

through the transistor from most positive to least positive and in the direction of thearrow on the emitter. In Figure 5.8a, the transistor has a positive power supply withground on the emitter. If the input is also positive, the transistor will conduct. If theinput goes negative, as in Figure 5.8b, the conduction of the device stops becausethe input, or in this case the base junction, controls the transistor condition. Noticethat when current flows, it does so in the direction of the arrow. The same rules thatapply to transistors hold true with diodes. However, diodes are simpler thantransistors because they have only one junction and conduct in only one direction.Note these simple rules will not allow you to read all electronic schematics, they willaid in understanding some of the basic concepts.To assist in your understanding of reading symbols and schematics, answerthe following questions:Using figure 5.7 attempt answering the following questions;1a. List the number which corresponds to Coil or inductor, PNPtransistor, diode, positive power supply, fixed resistor, capacitor, NPN, transistor,variable resistor, negative power supply, circuit ground, potentiometer.b. What is the value of R13? (Include units)c. With the input to Q1 at -15 volts, will the transistor be conducting ornonconducting?Give reasons for your answer.d. What is the value of C1? (Include units)

2.

Figure 5.9.

these components;

Use Figure 5.9 and 5.10 to answer the following:

1-5VDC

INPUTINPUT

+15

+

-

U2

-15

CR3 R13

R14

O2

O3

R20

C7

R12 1�

R11

15R1

250�

RL

24VDC

CR4 9

115

figure 5.10 100W inverter.

How many resistors are there in the circuit?b. How many transistors are there? , are they PNP or NPN transistors?c. What is Cr4?d. How many power supplies are there feeding the circuit and its components?e. How many capacitors are in the circuit?f. Will conduct when the output of U2 is a positive or negative voltage?

5.8. Reading Logic DiagramsWhen reading logic prints we must decide the input values to each gate. Butoccasionally the print will provide information as to the normal state of each logicgate. This is denoted by a symbol similar to the bistable symbol. The symbol isdrawn so that the first part of the square wave indicates the normal state of the gate.The second part of the square wave indicates the off-normal state of the gate.Reading a logic diagram that does not provide information on the status of the gatesis not any more difficult. It simply requires the reader to choose the initialconditions, determine the response of the circuits, and modify the inputs as needed.

+12V C2220uF50V

Q5

R7

0.1 Ohm5 Watt

R6

0.1 Ohm5 Watt

F110A

Fuse

12

0 T1

220 VAC out

12D1

BY 127

D29.1V

4 5 6

Q1

Q6

R2

4.7K

IC1 = CD4047

3

210

IC1

11

7 8 9

1

250K

0.022uF

C1

R1

4.7K

R3

Q1 & Q2 = TIR122

Q3 Io Q4= 2N3055

Q2

100W INVERTER

0.1 Ohm

R5

5 WattQ3

R40.1 Ohm5 Watt

Q4

116

Figure 5.11. Example of a Logic Print

Logic diagrams and prints can be used to depict several types of information. Themost common use is to provide a simplified functional representation of anelectrical circuit, as illustrated in Figure 5.11. it is easier and faster to understandhow a valve functions and responds to various inputs signals by representing avalve circuit using logic symbols, than by using the electrical schematic with itscomplex relays and contacts. Note that these drawings do not replace schematics,but they are easier to use for certain applications.

Why Read Electrical Electronic DiagramsIt is absolutely essential that personnel in the electrical or electronic profession beable to "read" (interpret) various types of electrical diagrams. Each of the variousdiagrams has a specific purpose and distinguishing features that set it apart fromthe others. The diagrams may be used for the following purposes:

O

b

D

dB

A

C

D

E

e

G

F

f

g

�

117

To learn a specific system operationTo locate the components of a systemTo identify the components of a systemTo trace a circuitThe troubleshoot equipmentThe repair equipment.

118