ELECTRONICS ENGINEERING 1

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ELECTRONICS ENGINEERING 1

INTRODUCTION

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the science dealing with the development and application of devices and systems involving the flow of electrons or other carriers of electric charge, in a vacuum, in gaseous media, in plasma, in semiconductors, in solid-state and/or in similar devices, including, but not limited to, applications involving optical, electromagnetic and other energy forms when transduced or converted into electronic signals.

ELECTRONICS

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APPLICATIONS OF ELECTRONICS

COMMUNICATIONS ELECTRONICS ELECTRIC POWER DIGITAL ELECTRONICS AUTOMOTIVE ELECTRONICS INDUSTRIAL ELECTRONICS MEDICAL ELECTRONICS CONSUMER ELECTRONICS

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2 TYPES OF ELECTRONIC SIGNAL

ANALOG – ELECTRONIC SIGNALS THAT THE AMPLITUDE CHANGES CONTINUOUSLY WITH RESPECT TO TIME WITH NO BREAKS OR DISCONTINUITIES.

DIGITAL – ELECTRONIC SIGNALS THAT ARE DESCRIBE AS DISCRETE; THEIR AMPLITUDE MAINTAINS A CONSTANT LEVEL FOR A PRESCRIBED PERIOD OF TIME THEN IT CHANGES TO ANOTHER LEVEL.

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TWO TYPES OF ELECTRONIC CIRCUIT

DISCRETE CIRCUIT – Electronic circuit that is composed of individual circuit components.

INTEGRATED CIRCUIT (IC) – Electronic circuit with thousands of circuit components in a single package.

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CLASSIFICATIONS OF ELECTRONIC COMPONENTS ACCORDING TO FUNCTION

ACTIVE SEMICONDUCTORS ELECTRON TUBES VDD (Visual Display Devices)

PASSIVERESISTOR, CAPACITOR & INDUCTOR

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ELECTRONIC COMPONENTS

SEMICONDUCTORSDIODE, TRANSISTOR, ICs, etc.

RESISTORS CAPACITORS INDUCTOR/ COIL ELECTRON TUBES

VACUUM TUBES, PICTURE TUBES, CRT (Cathode Ray Tube) VISUAL DISPLAY DEVICES

LCD (Liquid Crystal Display)LED ( Light Emitting Diode)

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ELECTRONIC CIRCUIT REPRESENTATION (ELECTRONIC CIRCUIT DIAGRAM)

Block Diagram Circuit Diagram (Schematic) Pictorial Diagram

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Block Diagrams

Block diagrams are used to understand (and design) complete circuits by breaking them down into smaller sections or blocks.

Each block performs a particular function and the block diagram shows how they are connected together.

No attempt is made to show the components used within a block, only the inputs and outputs are shown. This way of looking at circuits is called the systems approach.

Power supply (or battery) connections are usually not shown on block diagrams.

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Audio Amplifier System

• The power supply (not shown) is connected to the pre-amplifier and power amplifier blocks.

• Microphone - a transducer which converts sound to voltage. • Pre-Amplifier - amplifies the small audio signal (voltage) from the

microphone. • Tone and Volume Controls - adjust the nature of the audio signal.

The tone control adjusts the balance of high and low frequencies. The volume control adjusts the strength of the signal.

• Power Amplifier - increases the strength (power) of the audio signal. • Loudspeaker - a transducer which converts the audio signal to sound.

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Radio Receiver System                                                                                                                                                                                

• The power supply (not shown) is connected to the audio amplifier block.

• Aerial - picks up radio signals from many stations.• Tuner - selects the signal from just one radio station. • Detector - extracts the audio signal carried by the radio signal. • Audio Amplifier - increases the strength (power) of the audio signal.• Loudspeaker - a transducer which converts the audio signal to

sound.

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Regulated Power Supply System

• Transformer - steps down 230V AC mains to low voltage AC. • Rectifier - converts AC to DC, but the DC output is varying. • Smoothing - smooths the DC from varying greatly to a small ripple. • Regulator - eliminates ripple by setting DC output to a fixed

voltage.

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Feedback Control System

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Feedback Control System

• The power supply (not shown) is connected to the control circuit block.

• Sensor - a transducer which converts the state of the controlled quantity to an electrical signal.

• Selector (control input) - selects the desired state of the output. Usually it is a variable resistor.

• Control Circuit - compares the desired state (control input) with the actual state (sensor) of the controlled quantity and sends an appropriate signal to the output transducer.

• Output Transducer - converts the electrical signal to the controlled quantity.

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Feedback Control System

• Controlled Quantity - usually not an electrical quantity, e.g. motor speed.

• Feedback Path - usually not electrical, the Sensor detects the state of the controlled quantity.

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Circuit Diagram

Circuit diagrams show how electronic components are connected together. Each component is represented by a symbol.

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Wires and Connections

component circuit symbol function

Wire ________ To pass current very easily from one part of a circuit to another.

Wires joined

A 'blob' should be drawn where wires are connected (joined), but it is sometimes omitted. Wires connected at 'crossroads' should be staggered slightly to form two T-junctions.

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Wires and Connections

component

circuit symbol function

Wires not 

joined

In complex diagrams it is often necessary to draw wires crossing even though they are not connected. The 'hump' symbol is preferable because the simple crossing on the left may be misread as a join where you have forgotten to add.

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Wires and Connections

component

circuit symbol function

Cell Supplies electrical energy. A single cell is often wrongly called a battery, but strictly a battery is two or more cells joined together.

Battery Supplies electrical energy. A battery is more than one cell.

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Wires and Connections

component

circuit symbol function

DC supply Supplies electrical energy.DC = Direct Current, always flowing in one direction.

AC supply Supplies electrical energy.AC = Alternating Current, continually changing direction.

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Power Supplies

component

circuit symbol function

fuse A safety device which will 'blow' (melt) if the current flowing through it exceeds a specified value.

transformer

Two coils of wire linked by an iron core. Transformers are used to step up (increase) and step down (decrease) AC voltages. Energy is transferred between the coils by the magnetic field in the core. There is no electrical connection between the coils.

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Power Supplies

component

circuit symbol

function

Earth (ground)

A connection to earth. For many electronic circuits this is the 0V (zero volts) of the power supply, but for mains electricity and some radio circuits it really means the earth. It is also known as ground.

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Output Devices: Lamps, Heater, Motor, etc.

Component

Circuit Symbol Function

Lamp (lighting)

A transducer which converts electrical energy to light. This symbol is used for a lamp providing illumination, for example a car headlamp or torch bulb.

Lamp (indicator)

A transducer which converts electrical energy to light. This symbol is used for a lamp which is an indicator, for example a warning light on a car dashboard.

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Output Devices: Lamps, Heater, Motor, etc.

Component

Circuit Symbol Function

Heater A transducer which converts electrical energy to heat.

Motor A transducer which converts electrical energy to kinetic energy (motion).

Bell A transducer which converts electrical energy to sound.

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Output Devices: Lamps, Heater, Motor, etc.

Component

Circuit Symbol Function

Buzzer A transducer which converts electrical energy to sound.

Inductor(Coil,

Solenoid)

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

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Switches

Component

Circuit Symbol Function

Push Switch a. push-to-make

A push switch allows current to flow only when the button is pressed. This is the switch used to operate a doorbell.

b. push-to-break

This type of push switch is normally closed (on), it is open (off) only when the button is pressed.

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Switches

Component

Circuit Symbol Function

On-Off Switch(SPST)

SPST = Single Pole, Single Throw. An on-off switch allows current to flow only when it is in the closed (on) position.

2-way Switch (SPDT)

SPDT = Single Pole, Double Throw. A 2-way changeover switch directs the flow of current to one of two routes according to its position. Some SPDT switches have a central off position and are described as 'on-off-on'.

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Switches

Component

Circuit Symbol Function

Dual On-Off Switch(DPST)

DPST = Double Pole, Single Throw. A dual on-off switch which is often used to switch mains electricity because it can isolate both the live and neutral connections.

Reversing Switch(DPDT)

DPDT = Double Pole, Double Throw. This switch can be wired up as a reversing switch for a motor. Some DPDT switches have a central off position.

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Switches

Component

Circuit Symbol Function

Relay An electrically operated switch, for example a 9V battery circuit connected to the coil can switch a 230V AC mains circuit.NO = Normally Open, COM = Common, NC = Normally  Closed.

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Circuit Diagram and Component Layouts

Circuit diagrams show the connections as clearly as possible with all wires drawn neatly as straight lines.

The actual layout of the components is usually quite different from the circuit diagram.

A circuit diagram is useful when testing a circuit and for understanding how it works.

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Drawing Circuit Diagrams

not difficult but it takes a little practice to draw neat, clear diagrams

a useful skill for science as well as for electronics You will certainly need to draw circuit diagrams if you

design your own circuits

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Drawing Circuit Diagrams

Follow these tips for best results: Make sure you use the correct symbol for each

component. Draw connecting wires as straight lines (use a

ruler). Put a 'blob' ( • ) at each junction between wires. Label components such as resistors and capacitors

with their values. The positive (+) supply should be at the top and

the negative (-) supply at the bottom. The negative supply is usually labeled 0V, zero

volts.

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Drawing Complex Circuit Diagrams

Try to arrange the diagram so that signals flow from left to right: inputs and controls should be on the left, outputs on the right.

You may omit the battery or power supply symbols, but you must include (and label) the supply lines at the top and bottom.

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End of Lesson 1