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DTMF Based Robot EMBEDDED SYSTEM The embedded system is a combination of computer hardware, software additional electrical & mechanical parts. A computer is used in such devices primarily as a means to simplify the system design and to provide flexibility. Often the user of the device is not even aware that a computer is present. Electronic devices that incorporate a computer (usually a microprocessor) within their implementation These are Real-time systems process events. These events occur on external inputs cause other events to occur as outputs. Minimizing response time is usually a primary objective, or otherwise the entire system may fail to operate properly. Therefore embedded systems employ the use of a RTOS (Real-Time Operating System) It’s an operating Systems with the necessary features to support a Real-Time System Real-Time System BBDNITM, LKO 1
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EMBEDDED SYSTEM

The embedded system is a combination of computer hardware, software additional electrical & mechanical parts.

A computer is used in such devices primarily as a means to simplify the system design and to provide flexibility.

• Often the user of the device is not even aware that a computer is present.

• Electronic devices that incorporate a computer (usually a microprocessor) within their implementation

These are Real-time systems process events. These events occur on external inputs cause other events to occur as outputs. Minimizing response time is usually a primary objective, or otherwise the entire system may fail to operate properly.

Therefore embedded systems employ the use of a RTOS (Real-Time Operating System)It’s an operating Systems with the necessary features to support a Real-Time System

Real-Time System

A system where correctness depends not only on the correctness of the logical result of the computation, but also on the result delivery time. It responds in a timely, predictable way to unpredictable external stimuli arrivals.

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The real Time Systems can be further divided into two types: Soft Real-Time System:Compute output response as fast as

possible, but no specific deadlines that must be met. Hard Real-Time System: Output response must be computed by

specified deadline or system.

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APPLICATION OF EMBEDDED SYSTEMS IN SPHERE OF LIFE

Consumer electronics Telecommunication Automobile Medical instrumentation Industrial control equipment Defense Communication satellite Data communication Internet appliances

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DUAL TONE MULTI FREQUENCY

Dual-tone multi frequency (DTMF), also known as Touch Tone or Tone Dialing, is used for telephone signaling over the line in the voice frequency band to the call switching center. DTMF is an example of a multi frequency shift keying (MFSK) system. Today DTMF is used for most call setup to the telephone exchange, at least in the Western world, and trunk signaling is now done out of band using the SS7 signaling system. The in band trunk signaling tones were different from the tones known as touch tone with a triangular matrix being used rather than a square matrix.

Prior to DTMF the phone systems had used a system known as pulse or loop disconnect (LD) signaling to dial numbers, which works by rapidly disconnecting and connecting the calling party's phone line, like flicking a light switch on and off. The repeated connection and disconnection sounds like a series of clicks. The LD range was restricted for technical reasons, and placing calls over longer distances required either operator assistance or the provision of subscriber trunk dialing equipment.

DTMF was developed at Bell Labs in order to allow dialing signals to dial long-distance numbers, potentially over non wire links such as microwave links or satellites. Encoder/decoders were added at the end offices that would convert the standard pulse signals into DTMF tones and play them down the line to the remote end office. At the remote site another encoder/decoder would decode the tones and perform pulse dialing. It was as if you were connected directly to that end office, yet the signaling would work over any sort of link. This idea of using the existing network for signaling as well as the message is known as in-band signaling.

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It was clear even in the late 1950s when DTMF was being developed that the future of switching lay in electronic switches, as opposed to the mechanical crossbar systems then in use. In this case pulse dialing made no sense at any point in the circuit, and plans were made to roll DTMF out to end users as soon as possible. Various tests of the system occurred throughout the 1960s where DTMF became known as Touch Tone.

The Touch Tone system also introduced a standardized keypad layout. After testing 18 different layouts, they eventually chose the one familiar to us today, with 1 in the upper-left and 0 at the bottom. The adding-machine layout, with 1 in the lower-left was also tried, but at that time few people used adding machines, and having the 1 at the "start" (in European language reading order) led to fewer typing errors. In retrospect, many people consider that this was a mistake. With the widespread introduction of computers and bank machines, the phone keyboard has become "oddball", causing mistakes.

The engineers had also envisioned phones being used to access computers, and surveyed a number of companies to see what they would need for this role. This led to the addition of the number sign (#) and star (*) keys, as well as a group of keys for menu selection, A, B, C and D. In the end the lettered keys were dropped from most phones, and it was many years before the # and * keys became widely used, primarily for certain vertical service codes such as *67 in the United States to suppress caller ID. Many non-telephone applications still use the alphabetic keys, such as amateur radio repeater signaling and control.

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DTMF DECODER

It is a signaling system used for dialing telephone numbers using a numeric keypad, Instead of Using the spinning dial on old pulse-dialing phone

Popularized under trademark name touch-tone The dtmf key is arranged in a 4*4 grid Each row of keys is assigned a particular low frequency and column of keys is assigned a particular high frequency. Every key is located at the intersection of a row and a column.

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DECODER IC: CM8870

Description:

The CAMD CM8870/70C provides full DTMF receiver capability by integrating both the band-split filter and digital decoder functions into a single 18-pin DIP, SOIC, or 20-pin PLCC package. The CM8870/70C is manufactured using state-of-the-art CMOS process technology for low power consumption (35mW, MAX) and precise data handling. The filter section uses a switched capacitor technique for both high and low group filters and dial tone rejection. The CM8870/70C decoder uses digital counting techniques for the detection and decoding of all 16 DTMF tone pairs into a 4-bit code. This DTMF receiver minimizes external component

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count by providing an on-chip differential input amplifier, clock generator,and a latched three-state interface bus. The on-chip clock generator requires only a low cost TV crystal orceramic resonator as an external component.

Features:

Full DTMF receiver Less than 35mW power consumption Industrial temperature range Uses quartz crystal or ceramic resonators Adjustable acquisition and release times 18-pin DIP, 18-pin DIP EIAJ, 18-pin SOIC, 20-pin PLCC

Applications:

PABX Central office Mobile radio Remote control Remote data entry Call limiting Telephone answering systems

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Pin diagram

Pin Description

IN+ Non-inverting input Connection to the front-end differential amplifierIN– Inverting input Connection to the front-end differential amplifierGS Gain select Gives access to output of front-end differential amplifier

for connectionof feedback resistor.

VREF Reference output Voltage May be used to bias the inputs at mid-rail.

(nominally VDD/2)INH Inhibits detection of tones Represents keys A, B, C, and D OSC3

Digital buffered oscillator output PD Power down Logic high powers down the device and inhibits the oscillator.OSC1 Clock input 3.579545MHz crystal connected between these pinsBBDNITM, LKO 9

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completes internal oscillatorOSC2 Clock output 3.579545MHz crystal connected between these pins

completes internal oscillatorVSS Negative power supply Normally connected to OVTOE Three-state output enable (Input) Logic high enables the outputs

Q1-Q4. Internal pull-up.Q1-Q4 Three-state ouputs When enabled by TOE, provides the code

corresponding to the last valid tone pair receivedStD Delayed Steering output Presents a logic high when a received tone

pair has been registered and the output latch is updated. Returns to logic low then the voltage on St/GT falls below VTSt.

ESt Early steering output Presents logic high immediately when the digital algorithm detects a recongnizable tone pair (signal condition). Any momentary loss of signal condition will cause ESt to return to a logic low.

St/GtSteering input/guard A voltage greater than VTSt detected at St causes the device to register time output (bidirectional) the dectected tone pair. The GT output acts to reset the external steering time constrant, and its state is a function of ESt and the voltage on St.

VDD Positve power supplyIC Internal connection Must be tied to VSS

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Internal Block Diagram

FUNCTIONAL DESCRIPTION

The CAMD CM8870/70C DTMF Integrated Receiver provides us with not only low power consumption, but high performance in a small 18-pin DIP, SOIC, or 20-pin PLCC package configuration. The CM8870/70C’s internal architecture consists of a band-split filter section which separates the high and low tones of the received pair, followed by a digital decode (counting) section which verifies both the frequency and duration of the received tones before passing the resultant 4-bit code to the output bus.

Decoder Section

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The CM8870/70C decoder uses a digital counting technique to determine the frequencies of the limited tones and to verify that these tones correspond to standard DTMF frequencies. A complex averaging algorithm is used to protect against tone simulation by extraneous signals (such as voice) while providing tolerance to small frequency variations. The averaging algorithm has been developed to ensure an optimum combination of immunity to “talk-off” and tolerance to the presence of interfering signals (third tones) and noise.

When the detector recognizes the simultaneous presence of two valid tones (known as “signal condition”), it raises the “Early Steering” flag (ESt). Any subsequent loss of signal condition will cause ESt to fall.

Steering Circuit

Before the registration of a decoded tone pair, the receiver checks for a valid signal duration (referred to as “character-recognition-condition”). This check is performed by an external RC time constant driven by ESt. A high logic on ESt causes VC (See Figure 4) to rise as the capacitor discharges. Providing signal condition is maintained (ESt remains high) for the validation period (tGTP), VC reaches the threshold (VTSt) of the steering logic to register the tone pair, thus latching its corresponding 4-bit code into the output latch. At this

point, the GT output is activated and drives VC to VDD.GT continues to drive high as long as ESt remains high, signaling that a received tone pair has been registered.

The contents of the output latch are made available on the 4-bit output bus by raising the three-state control input (TOE) to a logic high. The

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steering circuit works in reverse to validate the inter digit pause between signals.

Thus, as well as rejecting signals too short to be considered valid, the receiver will tolerate signal interruptions (drop outs) too short to be considered a valid pause.

This capability together with the capability of selecting the steering time constants externally, allows the designer to tailor performance to meet a wide variety of system requirements.

Guard Time Adjustment

In situations which do not require independent selection of receive and pause, the simple steering circuit of is applicable. Component values are chosen according to the following formula:

tREC = tDP + tGTP

tGTP = 0.67 RC

The value of tDP is a parameter of the device and tREC is the minimum signal duration to be recognized by the receiver. A value for C of 0.1μF is recommended for most applications, leaving R to be selected by the designer. For example, a suitable value of R for a tREC of 40ms would be 300K.The timing requirements for most telecommunication applications are satisfied with this circuit. Different steering arrangements may be used to select independently the guard-times for tone-present (tGTP) and tone absent (tGTA). This may be necessary to meet system specifications which place both accept and reject limits on both tone duration and interdigit pause.

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Guard time adjustment also allows the designer to tailor system parameters such as talk-off and noise immunity.Increasing tREC improves talk-off performance, since it reduces the probability that tones simulated by speech will maintain signal condition for long enough to be registered. On the other hand, a relatively short tREC with a long tDO would be appropriate for extremely noisy environments where fast acquisition time and immunity to drop-outs would be requirements.

Input Configuration

The input arrangement of the CM8870/70C provides a differential input operational amplifier as well as a bias source (VREF) which is used to bias the inputs at mid-rail. Provision is made for connection of a feedback resistor to the op-amp output (GS) for adjustment of gain. In a single-ended configuration, the input pins are connected as shown in Figure 1, with the op-amp connected for unity gain and VREF biasing the input at ½ VDD. Figure 6 shows the differential configuration, which permits the adjustment of gain with the feedback resistor R5.

Clock Circuit

The internal clock circuit is completed with the addition of a standard television color burst crystal or ceramic resonator having a resonant frequency of 3.579545MHz. The CM8870C in a PLCC package has a buffered oscillator output (OSC3) that can be used to drive clock inputs of other devices such as a microprocessor or other CM887X’s as shown in Figure 7. MultipleCM8870/70Cs can be connected as shown in figure 8 such that only one crystal or resonator is required.

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Circuit diagram of DTMF Decoder

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PCB Layout of DTMF Decoder

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RF COMMUNICATION

RF communication works by creating electromagnetic waves at a source and being able to pick up those electromagnetic waves at a particular destination. These electromagnetic waves travel through the air at near the speed of light. The wavelength of an electromagnetic signal is inversely proportional to the frequency; the higher the frequency, the shorter the wavelength.

Frequency is measured in Hertz (cycles per second) and radio frequencies are measured in kilohertz (KHz or thousands of cycles per second), megahertz (MHz or millions of cycles per second) and gigahertz (GHz or billions of cycles per second). Higher frequencies result in shorter wavelengths. The wavelength for a 900 MHz device is longer than that of a 2.4 GHz device.

In general, signals with longer wavelengths travel a greater distance and penetrate through, and around objects better than signals with shorter wavelengths.

How does an RF communication system work?

Imagine an RF transmitter wiggling an electron in one location. This wiggling electron causes a ripple effect, somewhat akin to dropping a pebble in a pond. The effect is an electromagnetic (EM) wave that travels out from the initial location resulting in electrons wiggling in remote locations. An RF receiver can detect this remote electron wiggling.

The RF communication system then utilizes this phenomenon by wiggling electrons in a specific pattern to represent information. The receiver can

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make this same information available at a remote location; communicating with no wires.

In most wireless systems, a designer has two overriding constraints: it must operate over a certain distance (range) and transfer a certain amount of information within a time frame (data rate). Then the economics of the system must work out (price) along with acquiring government agency approvals (regulations and licensing).

How is range determined?

In order to accurately compute range – it is essential to understand a few terms:

dB - Decibels

Decibels are logarithmic units that are often used to represent RF power. To convert from watts to dB: Power in dB = 10* (log x) where x is the power in watts.

Another unit of measure that is encountered often is dBm (dB milliwatts). The conversion formula for it is Power in dBm = 10* (log x) where x is the power in milliwatts.

Line-of-site (LOS)

Line-of-site when speaking of RF means more than just being able to see the receiving antenna from the transmitting antenna. In, order to have true line-of-site no objects (including trees, houses or the ground) can be in the Fresnel zone. The Fresnel zone is the area around the visual line-of-sight that radio waves spread out into after they leave the antenna. This area must be clear or else signal strength will weaken. BBDNITM, LKO 19

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There are essentially two parameters to look at when trying to determine range.

Transmit Power

Transmit power refers to the amount of RF power that comes out of the antenna port of the radio. Transmit power is usually measured in Watts, milliwatts or dBm. (For conversion between watts and dB see below.)

Receiver sensitivity

Receiver sensitivity refers to the minimum level signal the radio can demodulate. It is convenient to use an example with sound waves; Transmit power is how loud someone is yelling and receive sensitivity would be how soft a voice someone can hear. Transmit power and receive sensitivity together constitute what is know as “link budget”. The link budget is the total amount of signal attenuation you can have between the transmitter and receiver and still have communication occur.

Example: Maxstream 9XStream TX Power: 20dBm Maxstream 9XStream RX Sensitivity: -110dBm Total Link budget: 130dBm.

For line-of-site situations, a mathematical formula can be used to figure out the approximate range for a given link budget. For non line-of-site applications range calculations are more complex because of the various ways the signal can be attenuated.

RF communications and data rate

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Data rates are usually dictated by the system - how much data must be transferred and how often does the transfer need to take place. Lower data rates, allow the radio module to have better receive sensitivity and thus more range. In the XStream modules the 9600 baud module has 3dB more sensitivity than the 19200 baud module. This means about 30% more distance in line-of-sight conditions. Higher data rates allow the communication to take place in less time, potentially using less power to transmit.

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RF MODULE

Radio Frequency Module is an integral part of boarder security system together with a control module or unit and an antenna it is used for wireless identification. Main tasks of the RF module are to send an energizing signal via the antenna. The RF module delivers a digital data stream and a clock signal for further processing to its control unit or module. Furthermore a field strength dependent digital output is available for synchronization purposes.The RFM is tuned to resonance with the antenna by adjusting the inductance of thetuning coil at the RFM's output stage.RF Module can be categoried into two parts :

Transmitter Receiver

Transmitter

This wireless data is the easiest to use, lowest cost RF link we have ever seen! Use these components to transmit position data, temperature data, even current program register values wirelessly to the receiver. These modules have up to 500 ft range in open space. The transmitter operates from 2-12V. The higher the Voltage, the greater the range - see range test data in the documents section.We have used these modules extensively and have been very impressed with their ease of use and direct interface to an MCU. The theory of operation is very simple. What the transmitter 'sees' on its data pin is what the receiver outputs on its data pin. If you can configure the UART module on a PIC, you have an instant wireless data connection. The typical range is 500ft for open area.

This is an ASK transmitter module with an output of up to 8mW depending on power supply voltage. The transmitter is based on SAW BBDNITM, LKO 22

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resonator and accepts digital inputs, can operate from 2 to 12 Volts-DC, and makes building RF enabled products very easy.

Features:

434  MHz Transmitter Operation  500 Ft. Range - Dependent on Transmitter Power Supply 2400 or 4800bps transfer rate Low cost Extremely small and light weight

Receiver

This receiver type is good for data rates up to 4800bps and will only work with the 434MHz transmitter. Multiple 434MHz receivers can listen to one 434MHz transmitter. This wireless data is the easiest to use, lowest cost RF link we have ever seen! Use these components to transmit position data, temperature data, even current program register values wirelessly to the receiver. These modules have up to 500 ft range in open space. The receiver is operated at 5V. We have used these modules extensively and have been very impressed with their ease of use and direct interface to an MCU. The theory of operation is very simple. What the transmitter

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'sees' on its data pin is what the receiver outputs on its data pin. If you can configure the UART module on a PIC, you have an instant wireless data connection. Data rates are limited to 4800bps. The typical range is 500ft for open area. This receiver has a sensitivity of 3uV. It operates from 4.5 to 5.5 volts-DC and has digital output. The typical sensitivity is -103dbm and the typical current consumption is 3.5mA for 5V operation voltage. Features:

434 MHz Operation 500 Ft. Range - Dependent on Transmitter Power Supply 4800 bps transfer rate Low cost Extremely small and light weight

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IC: HT 12 E

Features

Operating voltage 2.4V~12V for the HT12E Low power and high noise immunity CMOS technology Low standby current: 0.1_A (typ.) at VDD=5V HT12A with a 38kHz carrier for infrared transmission medium Minimum transmission word four words for the HT12E Built-in oscillator needs only 5% resistor Data code has positive polarity Minimal external components HT12E: 18-pin DIP/20-pin SOP package

Applications

Burglar alarm system Smoke and fire alarm system Garage door controllers Car door controllers

General Description

The 212 encoders are a series of CMOS LSIs for remote control system applications. They arecapable of encoding information which consists of N address bits and 12_N data bits. Each address data input can be set to

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one of the two logic states. The programmed addresses data are transmitted together with the header bits via an RF or an infrared transmission medium upon receipt of a trigger signal. The capability to select a TE trigger on the HT12E or a DATA trigger on the HT12A further enhances the application flexibility of the 212 series of encoders.

Pin Diagram

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Block Diagram Of HT12E

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RF Transmitter Circuit Diagram

A,B,C & D are the signal received from the DTMF decoderJ: Connector For Power Supply 1: +ve terminal 2:–ve terminal

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RF Transmitter PCB Diagram

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IC: HT 12 D

Features Operatingvoltage:2.4V~12V Low power and high noise immunity CMOS technology Low standby current Capable of decoding 12 bits of information Binary address setting Received codes are checked 3times Address/Data number combination 8addressbitsand4databits Built-inoscillatorneedsonly5%resistor Validtransmissionindicator EasyinterfacewithanRForaninfraredtransmiss medium Minimalexternalcomponents 18-pinDIP,

Application: Burglar alarm system Smoke and fire alarms Garage door controllers Car door controllers Car alarm system Security system

General Description :

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The 1212 decoders are a series of CMOS LSIs for remote control system applications. They are paired with Holtek 1212 series of encoders. For proper operation, a pair of encoder/decoder with the same number of addresses and data format should be chosen. The decoders receive serial addresses and data from a programmed212 series of encoders that are transmitted by a carrier using an RF or an IR transmission medium. They compare the serial input data three times continuously with their local addresses. If no error or unmatched codes are found, the input data codes are decoded and then transferred to the output pins. The VT pin also goes high to indicate a valid transmission. The 212 series of decoders are capable of decoding informations that consist of N bits of address and 12 N bits of data. Of this series, the HT12D is arranged to provide 8 address bits and 4 data bits.

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Pin Diagram

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Block Diagram Of HT12D

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RF Receiver Circuit Diagram

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RF Receiver PCB Diagram

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MICROCONTROLLER

A microcontroller is a computer-on-a-chip, or, if you prefer, a single-chip computer. Micro suggests that the device is small, and controller tells you that the device might be used to control objects, processes, or events. Another term to describe a microcontroller is embedded controller, because the microcontroller and its support circuits are often built into, or embedded in, the devices they control.

You can find microcontrollers in all kinds of things these days. Any device that measures, stores, controls, calculates, or displays information is a candidate for putting a microcontroller inside. The largest single use for microcontrollers is in automobiles—just about every car manufactured today includes at least one microcontroller for engine control, and often more to control additional systems in the car. In desktop computers, you can find microcontrollers inside keyboards, modems, printers, and other peripherals. In test equipment, microcontrollers make it easy to add features such as the ability to store measurements, to create and store user routines, and to display messages and waveforms. Consumer products that use microcontrollers include cameras, video recorders, compact-disk players, and ovens. And these are just a few examples.

Microcontroller Basics

A microcontroller is similar to the microprocessor inside a personal computer. Examples of microprocessors include Intel’s 8086, Motorola’s 68000, and Zilog’s Z80. Both microprocessors and microcontrollers contain a central processing unit, or CPU. The CPU executes instructions that perform the basic logic, math, and data-moving functions of a

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computer. To make a complete computer, a microprocessor requires memory for storing data and programs, and input/output (I/O) interfaces for connecting external devices like keyboards and displays. In contrast, a microcontroller is a single-chip computer because it contains memory and I/O interfaces in addition to the CPU. Because the amount of memory and interfaces that can fit on a single chip is limited, microcontrollers tend to be used in smaller systems that require little more than the microcontroller and a few support components. Examples of popular microcontrollers are Intel’s 8052 (including the 8052-BASIC, which is the focus of this book), Motorola’s 68HC11, and Zilog’s Z8.

Microcontroller History

To understand how microcontrollers fit into the always-expanding world of computers, we need to look back to the roots of microcomputing.In its January 1975 issue, Popular Electronics magazine featured an article describing the Altair 8800 computer, which was the first microcomputer that hobbyists could build and program themselves. The basic Altair included no keyboard, video display, disk drives, or other elements we now think of as essential elements of a personal computer. Its 8080 microprocessor was programmed by flipping toggle switches on the front panel. Standard RAM was 256 bytes and a kit version cost $397 ($498 assembled). A breakthrough in the Altair’s usability occurred when a small company called Microsoft offered a version of the BASIC programming language for it. Of course, the computer world has changed a lot since the introduction of the Altair. Microsoft has become an enormous software publisher, and a typical personal computer now includes a keyboard, video display, disk drives, and Megabytes of RAM. What’s more, there’s no longer any need to build a personal computer

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from scratch, since mass production has drastically lowered the price of assembled systems. At most, building a personal computer now involves only installing assembled boards and other major components in an enclosure. A personal computer like Apple’s Macintosh or IBM’s PC is a general-purpose machine, since you can use it for many applications—word processing, spreadsheets, computer-aided design, and more—just by loading the appropriate software from disk into memory. Interfaces to personal computers are for the most part standard ones like those to video displays, keyboards, and printers.But along with cheap, powerful, and versatile personal computers has developed a new interest in small, customized computers for specific uses. Each of these small computers is dedicated to one task, or a set of closely related tasks. Adding computer power to a device can enable it to do more, or do it faster, better, or more cheaply. For example, automobile engine controllers have helped to reduce harmful exhaust emissions. And microcontrollers inside computer modems have made it easy to add features and abilities beyond the basic computer-to-phone-line interface. In addition to their use in mass-produced products like these, it’s also become feasible to design computer power into one-of-a-kind projects, such as an environmental controller for a scientific study or an intelligent test fixture that ensures that a product meets its specifications before it’s shipped to a customer. At the core of many of these specialized computers is a microcontroller. The computer’s program is typically stored permanently in semiconductor memory such as ROM or EPROM. The interfaces between the microcontroller and the outside world vary with the application, and may include a small display, a keypad or switches, sensors, relays, motors, and so on.These small, special-purpose computers are sometimes called single-board computers, or SBCs. The term can be misleading, however, since

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the computer doesn’t have to be on a single circuit board, and many types of computer systems, such as laptop and notebook computers, are now manufactured on a single board.

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AT89S8253 microcontroller

The microcontroller development effort resulted in the 8051 architecture, which was first introduced in 1980 and has gone on to be arguably the most popular micro controller architecture available. The 8051 is a very complete microcontroller with a large amount of built in control store (ROM &EPROM) and RAM, enhanced I/O ports, and the ability to access external memory. The maximum clock frequency with an 8051 micro controller can execute instructions is 20MHZ.Microcontroller is a true computer on chip. The design incorporates all of the features found in a microprocessor: CPU, ALU, PC, SP and registers. It also has the other features needed to, make complete computer: ROM, RAM, parallel I/O, serial I/O, counters and a clock circuit. The 89C51/89C52/89C54/89C58 contains a non-volatile FLASH program memory that is parallel programmable. For devices that are serial programmable(In-System Programmable (ISP) and In-Application Programmable (IAP) with a boot loader)All three families are Single-Chip 8-bit Microcontrollers manufactured in advanced CMOS process and are Derivatives of the 80C51 microcontroller family. All the devices have the same instruction set as the 80C51.

FEATURES

8K Bytes of In-System Reprogrammable Flash Memory Endurance: 1,000 Write/Erase Cycles Fully Static Operation: 0 Hz to 33 MHz Three-level Program Memory Lock 256 x 8-bit Internal RAM 32 Programmable I/O Lines

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Three 16-bit Timer/Counters Eight Interrupt Sources Programmable Serial Channel

DESCRIPTION:

The AT89s8253 is a low power, high performance CMOS 8-bit micro computer with 8K bytes of flash programmable and erasable read only memory(PEROM).The device is manufactured using Atmel’s high density nonvolatile memory technology and is compatible with the industry standard 80c51 and 80C52 instruction set and pin out.The on-chip flash allows the program memory to be reprogrammed insystem or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with flash on a monolithic chip, the Atmel AT89s8253 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications. The main advantages of 89s8253 over 8051 are

Software Compatibility Program Compatibility Rewritability

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89S8253 PROCESSOR ARCHITECTURE:

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8051 Architecture contains the following:

8 bit CPU with registers A and B 16 bit program counter(PC) and data pointer(DPTR) 8 bit program status word(PSW) 8 bit stack pointer Internal ROM of 0(8031) to 4K(8051) Internal RAM of 128 Bytes 4 register banks 00-1f 16 bytes(bit addressable) 20-2f 80 bytes of general purpose data memory 30-7f 32 I/O pins arranged as four 8 bit ports (P0 – P3) 2 16-bit timer/counters: T0 and T1 Full duplex serial data receiver/transmitter: SBUF Control registers: TCON, TMOD, SCON, PCON, IPand IE 2 external and 3 internal interrupt sources Oscillator and clock circuits

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Pin Diagram of the 40 Pin DIP package of the 89s8253

DESCRIPTION:

VCC Pin no.40 is used for the supply to the microcontroller..GND Ground.RST This is pin no.9, used to reset the device by keeping it high for 2 machine cycles. The microcontroller should be reset at the time of starting.Oscillator BBDNITM, LKO 45

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Pins XTAL1 and XTAL2 are used for connecting a quartz crystal for the internal oscillator.Crystal Frequency-10 MHzExternal Access(EA)The 8051 family members, all come with on-chip ROM to store the program. In such case, EA pin is connected to Vcc. To indicate that the code is stored in external ROM, EA pin must be connected to ground.PSENPSEN stands for Program Store Enable.This is an output pin and is connected to OE pin of ROMPort 0Port 0 is an 8-bit open drain bi-directional I/O port. As an output port,each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs. Port 0 can also be configured to be the multiplexed lower order address/data bus during accesses to external program and data memory. In this mode, P0 has internalpullups.Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification.External pullups are required during program verification.Port 1 and Port2Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count input (P1.0/T2) and the timer/counter 2.Port 3

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It has internal pull-ups and can sink/source 4 TTL inputs. Port 3 occupies a total of 8 pins, pins 10 through 17. It can be used as input or output. Port 3 has additional function of providing some extremely signal as interrupts.

ALE/PROG Address Latch Enable is an output pulse for latching the low byte of the address (on its falling edge) during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming. This pin is also the program pulse input (PROG) during Flash programming. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be used for external timing or locking purposes. Note, however, that one ALE pulse is skipped during each access to external data memory.

PSENProgram Store Enable. PSEN is the read strobe to external program memory (active low). When the AT89S8253 is executing code from external program memory, PSEN is activated twice each machine cycle,

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except that two PSEN activations are skipped during each access to external data memory.EA/VPPExternal Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming when 12-volt programming is selected.

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PCB Design of Receiver along with microcontroller

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MIKRO C

The mikroC for 8051 Compiler is a powerful feature-rich development tool for Atmel's 8051 microcontrollers. It is designed to provide the user with the easiest possible solution for developing applications for embedded systems without compromising on performance. Its highly advanced integrated development environment (IDE), broad set of library routines, ready-to-run and comprehensive documentation should be more than enough to get anyone off to a great start when developing 8051 applications.

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Features:

Advanced code editor to aid in the writing of source code.

Included libraries covering communications, data acquisition, displays and much more dramatically speed up development.

Code explorer allows you to monitor your program's structure, variables and functions.

Generates commented, human-readable assembly language files and HEX files compatible with any Atmel 8051 programmer.

Integrated simulator lets you inspect program flow and debug executable code.

Code Editor:

mikroC's code editor is an advanced text editor fashioned to satisfy the needs of professionals. Advanced editor features include adjustable syntax highlighting, code assistant offering an auto-complete function, auto-correction of common typos, the ability to comment/uncomment a block of code with single mouse-click and bookmarks that can be set to aid navigation through even the largest program code.

Code Explorer/Quick Help/Keyboard Shortcuts:

To the left of the main window area a pane contains mikroC's code explorer, quick-help. The code explorer tab provides a clear view of every declared item within the source code and from here you can jump to the declarations of those items.The quick help tab lists all the available built-in library functions as

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a helpful reference.Finally, the keyboard shortcuts tab lists all available keyboard shortcuts that may be used within mikroC.

Simulator

The source-level debugger is an integral component of the mikroC development environment and has been designed to simulate the operations of Atmel's 8051 microcontrollers to assist users in the debugging of their programs. The simulator simulates program flow and execution of instruction lines, although not operating in real-time it does not update timers, interrupt flags, etc.Once you have successfully compiled your project, you can run the simulator allowing you to carry out operations such as single-stepping code and running the code to a cursor position.A simulator watch window enables you to monitor program variables and registers of the 8051 with their values updated as you carry out simulation operations. Values changed as the simulation progresses are coloured red to clearly identify them. You can also edit values of variables and registers during the simulation process.A stopwatch window is also provided for use when simulating to calculate the processor cycles and execution time since the last debugger action.A view RAM window acts in a similar manner to the watch window and shows the contents of RAM, again with recently changed values highlighted in red and with the ability to manually change values.

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ULTRASONIC SENSOR

Ultrasonic sensors are commonly used for a wide variety of noncontact presence, proximity, or distance measuring applications. These devices typically transmit a short burst of ultrasonic sound toward a target, which reflects the sound back to the sensor. The system then measures the time for the echo to return to the sensor and computes the distance to the target using the speed of sound in the medium.

The wide variety of sensors currently on the market differ from one another in their mounting configurations, environmental sealing, and electronic features. Acoustically, they operate at different frequencies and have different radiation patterns. It is usually not difficult to select a sensor that best meets the environmental and mechanical requirements for a particular application, or to evaluate the electronic features available with different models. Still, many users may not be aware of the acoustic subtleties that can have major effects on ultrasonic sensor operation and the measurements being made with them.

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The overall intent of this article is to help the user select an ultrasonic sensor with the best acoustical properties, such as frequency and beam pattern, for a particular application, and how to obtain an optimum measurement from the sensor. The first step in this process is to gain a better understanding of how variations in the acoustical parameters of both the environment and the target affect the operation of the sensor. Specifically, the following variables will be discussed:

  • Variation in the speed of sound as a function of both temperature and the composition of the transmission medium, usually air, and how these variations affect sensor measurement accuracy and resolution  • Variation in the wavelength of sound as a function of both sound speed and frequency, and how this affects the resolution, accuracy, minimum target size, and the minimum and maximum target distances of an ultrasonic sensor  • Variation in the attenuation of sound as a function of both frequency and humidity, and how this affects the maximum target distance for an ultrasonic sensor in air  • Variation of the amplitude of background noise as a function of frequency, and how this affects the maximum target distance and minimum target size for an ultrasonic sensor  • Variation in the sound radiation pattern (beam angle) of both the ultrasonic transducer and the complete sensor system, and how this affects the maximum target distance and helps eliminate extraneous targets  • Variation in the amplitude of the return echo as a function of the target distance, geometry, surface, and size, and how this affects the maximum target distance attainable with an ultrasonic sensor

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Ultrasonic sound is a vibration at a frequency above the range of human hearing, usually >20 kHz. The microphones and loudspeakers used to receive and transmit the ultrasonic sound are called transducers. Most ultrasonic sensors use a single transducer to both transmit the sound pulse and receive the reflected echo, typically operating at frequencies between 40 kHz and 250 kHz. A variety of different types of transducers are used in these systems.The following sections provide an overview of how the sound pulse is affected by some of the fundamental ultrasonic properties of the medium in which the sound travels.

Speed of Sound in Air As a Function of Temperature

In an echo ranging system, the elapsed time between the emission of the ultrasonic pulse and its return to the receiver is measured. The range distance to the target is then computed using the speed of sound in the transmission medium, which is usually air. The accuracy of the target distance measurement is directly proportional to the accuracy of the speed of sound used in the calculation. The actual speed of sound is a function of both the composition and temperature of the medium through which the sound travels (see Figure 1).

 

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Figure 1. The speed of sound is plotted as a function of the temperature. At room temperature, sound travels at ~13,500 ips.

The speed of sound in air varies as a function of temperature by the relationship:

    (1)

where:

c(T) = speed of sound in air as a function of temperature in inches per second

T = temperature of the air in °C

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The speed of sound in different gaseous media is a function of the bulk modulus of the gas, and is affected by both the chemical composition and temperature. Table 1 gives the speed of sound for various gases at 0°C.

Ultrasonic sensors (also known as transceivers when they both send and receive) work on a principle similar to radar or sonar which evaluate attributes of a target by interpreting the echoes from radio or sound waves respectively. Ultrasonic sensors generate high frequency sound waves and evaluate the echo which is received back by the sensor. Sensors calculate the time interval between sending the signal and receiving the echo to determine the distance to an object.

This technology can be used for measuring: wind speed and direction (anemometer), fullness of a tank and speed through air or water. For measuring speed or direction a device uses multiple detectors and calculates the speed from the relative distances to particulates in the air or water. To measure the amount of liquid in a tank, the sensor measures the distance to the surface of the fluid. Further applications include: humidifiers, sonar, medical ultrasonography, burglar alarms and non-destructive testing.

Systems typically use a transducer which generates sound waves in the ultrasonic range, above 20,000 hertz, by turning electrical energy into sound, then upon receiving the echo turn the sound waves into electrical energy which can be measured and displayed.

The technology is limited by the shapes of surfaces and the density or consistency of the material. For example foam on the surface of a fluid in a tank could distort a reading.

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Transducers

Sound field of a non focusing 4MHz ultrasonic transducer with a near field length of N=67mm in water. The plot shows the sound pressure at a logarithmic db-scale.

Sound pressure field of the same ultrasonic transducer (4MHz, N=67mm) with the transducer surface having a spherical curvature with the curvature radius R=30mm

An ultrasonic transducer is a device that converts energy into ultrasound, or sound waves above the normal range of human hearing. While technically a dog whistle is an ultrasonic transducer that converts mechanical energy in the form of air pressure into ultrasonic sound waves, the term is more apt to be used to refer to piezoelectric BBDNITM, LKO 59

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transducers that convert electrical energy into sound. Piezoelectric crystals have the property of changing size when a voltage is applied, thus applying an alternating current (AC) across them causes them to oscillate at very high frequencies, thus producing very high frequency sound waves.

The location at which a transducer focuses the sound, can be determined by the active transducer area and shape, the ultrasound frequency and the sound velocity of the propagation medium.

The example shows the sound fields of an unfocused and a focusing ultrasonic transducer in water.

Detectors

Since piezoelectric crystals generate a voltage when force is applied to them, the same crystal can be used as an ultrasonic detector. Some systems use separate transmitter and receiver components while others combine both in a single piezoelectric transceiver.

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LM324 SINGLE SUPPLY QUAD OPERATIONAL AMPLIFIERS

The LM324 series are low–cost, quad operational amplifiers with true differential inputs. They have several distinct advantages over standard operational amplifier types in single supply applications. The quad -amplifier can operate at supply voltages as low as 3.0 V or as high as 32 V with quiescent currents about one–fifth of those associated with the MC1741 (on a per amplifier basis). The common necessity for external biasing components in many applications. The output voltage range also includes the negative power supply voltage.

Short Circuited Protected Outputs True Differential Input Stage Single Supply Operation: 3.0 V to 32 V (LM224, LM324, LM324A) Low Input Bias Currents: 100 nA Maximum (LM324A) Four Amplifiers Per Package Internally Compensated Common Mode Range Extends to Negative Supply Industry Standard Pin outs ESD Clamps on the Inputs Increase Ruggedness without Affecting Device Operation

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PIN CONNECTIONS :

LM324 AS A COMPARATOR SCHEMATIC DIAGRAM:

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COMPARATOR

An operational amplifier has a well balanced difference input and a very high gain. The parallels in the characteristics allows the op-amps to serve as comparators in some functions.

A standard op-amp operating in open loop configuration (without negative feedback) can be used as a comparator. When the non-inverting input (V+) is at a higher voltage than the inverting input (V-), the high gain of the op-amp causes it to output the most positive voltage it can. When the non-inverting input (V+) drops below the inverting input (V-), the op-amp outputs the most negative voltage it can. Since the output voltage is limited by the supply voltage, for an op-amp that uses a balanced, split supply, (powered by ± VS) this action can be written:

where sgn(x) is the sign function. Generally, the positive and negative supplies VS will not match absolute value:

when else when

In practice, using an operational amplifier as a comparator presents several disadvantages as compared to using a dedicated comparator: Op amps are designed to operate in the linear mode with negative feedback. Hence, an opamp typically has a lengthy recovery time from saturation. Almost all opamps have an internal compensation capacitor which

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imposes slew rate limitations for high frequency signals. Consequently an op amp makes a sloppy comparator with propagation delay that can be as slow as tens of microseconds.

1. Since op amps do not have any internal hysteresis an external hysteresis network is always necessary for slow moving input signals.

2. The quiescent current specification of an op amp is valid only when the feedback is active. Some op amps show an increased quiescent current when the inputs are not equal.

3. A comparator is designed to produce well limited output voltages that easily interface with digital logic. Compatibility with digital logic must be verified while using an op amp as a comparator.

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L293DMotor Driver and H-Bridges

The most common method to drive DC motors in two directions under control of a computer is with an H-bridge motor driver. H-bridges can be built from scratch with bi-polar junction transistors (BJT) or with field effect transistors (FET), or can be purchased as an integrated unit in a single integrated circuit package such as the L293. The L293 is simplest and inexpensive for low current motors, For high current motors, it is less expensive to build your own H-bridge from scratch.

The L293 is an integrated circuit motor driver that can be used for simultaneous, bi-directional control of two small motors. Small means small. The L293 is limited to 600 mA , but in reality can only handle much small currents unless you have done some serious heat sinking to keep the case temperature down. Unsure about whether the L293 will work with your motor? Hook up the circuit and run your motor while keeping your finger on the chip. If it gets too hot to touch, you can't use it with your motor.

The L293D is a quadruple high-current half-H driver designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to36 V. It is designed to drive inductive loads such as relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage loads in positive-supply applications .All inputs are TTL-compatible. Each output is a complete totem-pole drive circuit with a Darlington transistor sink and a pseudo-Darlington source. Drivers are enabled in pairs with drivers 1 and 2enabled by 1,2EN and drivers 3 and 4 enabled b3,4 EN. When an enable input is high,the associated drivers are enabled, and their outputs are active and in phase with their inputs. External high-speed output

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clamp diodes should be used for inductive transient suppression. When the enable input is low, those drivers are disabled, and their outputs are off and in a high-impedance state. With the proper data inputs, each pair of drivers form a full-H (or bridge) reversible drive suitable for solenoid or motor applications.

L293D is a bipolar motor driver IC. This is a high voltage, high current push pull four channel driver compatible to TTL logic levels and drive inductive loads. It has 600 mA output current capability per channel and internal clamp diodes. The L293 is designed to provide bidirectional drive currents of upto 1A at voltages from 4.5 V to 36 V. The L293D is designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V. Both devices are designed to drive inductive loads such as relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage loads in positive supply applications. All inputs are TTL compatible. Each output is a complete totem-pole drive circuit, with a Darlington transistor sink and a pseudo-Darlington source.

Drivers are enabled in pairs, with drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN. When an enable input is high, the associated drivers are enabled, and their outputs are active and in phase with their inputs. When the enable input is low, those drivers are disabled, and their outputs are off and in the high-impedance state. With the proper data inputs, each pair of drivers forms a full-H (or bridge) reversible drive suitable for solenoid or motor applications

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FEATURES

600-mA Output Current Capability Per Driver Pulsed Current 1.2-A Per Driver Output Clamp Diodes for Inductive Transient Suppression Wide Supply Voltage Range 4.5 V to 36 V Separate Input-Logic Supply Thermal Shutdown Internal ESD Protection High-Noise-Immunity Inputs Functional Replacement for SGS L293D

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PIN DIAGRAM:

LOGIC DIAGRAM:

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FUNCTION TABLE:

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SCHEMATIC DIAGRAM:

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PCB LAYOUT:

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DC MOTORA DC motor is designed to run on DC electric power. Two examples of pure DC designs are Michael Faraday's homopolar motor (which is uncommon), and the ball bearing motor, which is (so far) a novelty. By far the most common DC motor types are the brushed and brushless types, which use internal and external commutation respectively to create an oscillating AC current from the DC source—so they are not purely DC machines in a strict sense.Brushed DC motorThe classic DC motor design generates an oscillating current in a wound rotor, or armature, with a split ring commutator, and either a wound or permanent magnet stator. A rotor consists of one or more coils of wire wound around a core on a shaft; an electrical power source is connected to the rotor coil through the commutator and its brushes, causing current to flow in it, producing

electromagnetism. The commutator causes the current in the coils to be switched as the rotor turns, keeping the magnetic poles of the rotor from ever fully aligning with the magnetic poles of the stator field, so that the

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rotor never stops (like a compass needle does) but rather keeps rotating indefinitely (as long as power is applied and is sufficient for the motor to overcome the shaft torque load and internal losses due to friction, etc.)

Many of the limitations of the classic commutator DC motor are due to the need for brushes to press against the commutator. This creates friction. At higher speeds, brushes have increasing difficulty in maintaining contact. Brushes may bounce off the irregularities in the commutator surface, creating sparks. (Sparks are also created inevitably by the brushes making and breaking circuits through the rotor coils as the brushes cross the insulating gaps between commutator sections. Depending on the commutator design, this may include the brushes shorting together adjacent sections—and hence coil ends—momentarily while crossing the gaps. Furthermore, the inductance of the rotor coils causes the voltage across each to rise when its circuit is opened, increasing the sparking of the brushes.) This sparking limits the maximum speed of the machine, as too-rapid sparking will overheat, erode, or even melt the commutator. The current density per unit area of the brushes, in combination with their resistivity, limits the output of the motor. The making and breaking of electric contact also causes electrical noise, and the sparks additionally cause RFI. Brushes eventually wear out and require replacement, and the commutator itself is subject to wear and maintenance (on larger motors) or replacement (on small motors). The commutator assembly on a large machine is a costly element, requiring precision assembly of many parts. On small motors, the

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commutator is usually permanently integrated into the rotor, so replacing it usually requires replacing the whole rotor.Large brushes are desired for a larger brush contact area to maximize motor output, but small brushes are desired for low mass to maximize the speed at which the motor can run without the brushes excessively bouncing and sparking (comparable to the problem of "valve float" in internal combustion engines). (Small brushes are also desirable for lower cost.) Stiffer brush springs can also be used to make brushes of a given mass work at a higher speed, but at the cost of greater friction losses (lower efficiency) and accelerated brush and commutator wear. Therefore, DC motor brush design entails a trade-off between output power, speed, and efficiency/wear.

A: shuntB: seriesC: compoundf = field coil

There are five types of brushed DC motor:A. DC shunt wound motorB. DC series wound motorC. DC compound motor (two configurations):

Cumulative compound Differentially compoundedD. Permanent Magnet DC Motor (not shown)E. Separately-excited (sepex) (not shown).BBDNITM, LKO 77

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Brushless DC motorsSome of the problems of the brushed DC motor are eliminated in the brushless design. In this motor, the mechanical "rotating switch" or commutator/brushgear assembly is replaced by an external electronic switch synchronised to the rotor's position. Brushless motors are typically 85-90% efficient or more (higher efficiency for a brushless electric motor of up to 96.5% were reported by researchers at the Tokai University in Japan in 2009),[14] whereas DC motors with brushgear are typically 75-80% efficient.

Midway between ordinary DC motors and stepper motors lies the realm of the brushless DC motor. Built in a fashion very similar to stepper motors, these often use a permanent magnet external rotor, three phases of driving coils, one or more Hall effect sensors to sense the position of the rotor, and the associated drive electronics. The coils are activated, one phase after the other, by the drive electronics as cued by the signals from either Hall effect sensors or from the back EMF (electromotive force) of the undriven coils. In effect, they act as three-phase synchronous motors containing their own variable-frequency drive electronics. A specialized class of brushless DC motor controllers utilize EMF feedback through the main phase connections instead of Hall effect sensors to determine position and velocity. These motors are used extensively in electric radio-controlled vehicles. When configured with the BBDNITM, LKO 78

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magnets on the outside, these are referred to by modelists as outrunner motors.Brushless DC motors are commonly used where precise speed control is necessary, as in computer disk drives or in video cassette recorders, the spindles within CD, CD-ROM (etc.) drives, and mechanisms within office products such as fans, laser printers and photocopiers. They have several advantages over conventional motors:

Compared to AC fans using shaded-pole motors, they are very efficient, running much cooler than the equivalent AC motors. This cool operation leads to much-improved life of the fan's bearings.

Without a commutator to wear out, the life of a DC brushless motor can be significantly longer compared to a DC motor using brushes and a commutator. Commutation also tends to cause a great deal of electrical and RF noise; without a commutator or brushes, a brushless motor may be used in electrically sensitive devices like audio equipment or computers.

The same Hall effect sensors that provide the commutation can also provide a convenient tachometer signal for closed-loop control (servo-controlled) applications. In fans, the tachometer signal can be used to derive a "fan OK" signal.

The motor can be easily synchronized to an internal or external clock, leading to precise speed control.

Brushless motors have no chance of sparking, unlike brushed motors, making them better suited to environments with volatile chemicals and fuels. Also, sparking generates ozone which can accumulate in poorly ventilated buildings risking harm to occupants' health.

Brushless motors are usually used in small equipment such as computers and are generally used to get rid of unwanted heat.

They are also very quiet motors which is an advantage if being used in equipment that is affected by vibrations.

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Modern DC brushless motors range in power from a fraction of a watt to many kilowatts. Larger brushless motors up to about 100 kW rating are used in electric vehicles. They also find significant use in high-performance electric model aircraft.

Coreless or ironless DC motorsNothing in the design of any of the motors described above requires that the iron (steel) portions of the rotor actually rotate; torque is exerted only on the windings of the electromagnets. Taking advantage of this fact is the coreless or ironless DC motor, a specialized form of a brush or brushless DC motor. Optimized for rapid acceleration, these motors have a rotor that is constructed without any iron core. The rotor can take the form of a winding-filled cylinder, or a self-supporting structure comprising only the magnet wire and the bonding material. The rotor can fit inside the stator magnets; a magnetically-soft stationary cylinder inside the rotor provides a return path for the stator magnetic flux. A second arrangement has the rotor winding basket surrounding the stator magnets. In that design, the rotor fits inside a magnetically-soft cylinder that can serve as the housing for the motor, and likewise provides a return path for the flux.Because the rotor is much lighter in weight (mass) than a conventional rotor formed from copper windings on steel laminations, the rotor can accelerate much more rapidly, often achieving a mechanicaltime constant under 1 ms. This is especially true if the windings use aluminum rather than the heavier copper. But because there is no metal mass in the rotor to act as a heat sink, even small coreless motors must often be cooled by forced air.Related limited-travel actuators have no core and a bonded coil placed between the poles of high-flux thin permanent magnets. These are the fast head positioners for rigid-disk ("hard disk") drives.

Printed Armature or Pancake DC Motors

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A rather unique motor design the pancake/printed armature motor has the windings shaped as a disc running between arrays of high-flux magnets, arranged in a circle, facing the rotor and forming an axial air gap. This design is commonly known the pancake motor because of its extremely flat profile, although the technology has had many brand names since it's inception, such as ServoDisc.The printed armature (originally formed on a printed circuit board) in a printed armature motor is made from punched copper sheets that are laminated together using advanced composites to form a thin rigid disc. The printed armature has a unique construction, in the brushed motor world, in that is does not have a separate ring commutator. The brushes run directly on the armature surface making the whole design very compact.An alternative manufacturing method is to use wound copper wire laid flat with a central conventional commutator, in a flower and petal shape. The windings are typically stabilized by being impregnated with electrical epoxy potting systems. These are filled epoxies that have moderate mixed viscosity and a long gel time. They are highlighted by low shrinkage and low exotherm, and are typically UL 1446 recognized as a potting compound for use up to 180°C (Class H) (UL File No. E 210549).The unique advantage of ironless DC motors is that there is no cogging (vibration caused by attraction between the iron and the magnets) and parasitic eddy currents cannot form in the rotor as it is totally ironless. This can greatly improve efficiency, but variable-speed controllers must use a higher switching rate (>40 kHz) or direct current because of the decreased electromagnetic induction.These motors were originally invented to drive the capstan(s) of magnetic tape drives, in the burgeoning computer industry. Pancake motors are still widely used in high-performance servo-controlled systems, humanoid robotic systems, industrial automation and medical devices. Due to the variety of constructions now available the technology

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is used in applications from high temperature military to low cost pump and basic servo applications.

NOTE: Here we used GEARED DC motor

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STEPPER MOTOR:

A stepper motor (or step motor) is a brushless, synchronous electric motor that can divide a full rotation into a large number of steps. The motor's position can be controlled precisely without any feedback mechanism, as long as the motor is carefully sized to the application. Stepper motors are similar to switched reluctance motors (which are very large stepping motors with a reduced pole count, and generally are closed-loop commutated

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Fundamentals of Operation

Stepper motors operate differently from DC brush motors, which rotate when voltage is applied to their terminals. Stepper motors, on the other hand, effectively have multiple "toothed" electromagnets arranged around a central gear-shaped piece of iron. The electromagnets are energized by an external control circuit, such as a microcontroller. To make the motor shaft turn, first one electromagnet is given power, which makes the gear's teeth magnetically attracted to the electromagnet's teeth. When the gear's teeth are thus aligned to the first electromagnet, they are slightly offset from the next electromagnet. So when the next electromagnet is turned on and the first is turned off, the gear rotates slightly to align with the next one, and from there the process is repeated. Each of those slight rotations is called a "step," with an integer number of steps making a full rotation. In that way, the motor can be turned by a precise angle

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Stepper motor characteristics

1. Stepper motors are constant power devices.2. As motor speed increases, torque decreases.3. The torque curve may be extended by using current limiting drivers

and increasing the driving voltage.4. Steppers exhibit more vibration than other motor types, as the

discrete step tends to snap the rotor from one position to another.5. This vibration can become very bad at some speeds and can cause

the motor to lose torque.6. The effect can be mitigated by accelerating quickly through the

problem speeds range, physically damping the system, or using a micro-stepping driver.

7. Motors with a greater number of phases also exhibit smoother operation than those with fewer phases.

Types Of Stepper Motor

There are three main types of stepper motors:

1. Permanent Magnet Stepper2. Hybrid Synchronous Stepper

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3. Variable Reluctance Stepper

Permanent magnet motors use a permanent magnet (PM) in the rotor and operate on the attraction or repulsion between the rotor PM and the stator electromagnets. Variable reluctance (VR) motors have a plain iron rotor and operate based on the principle of that minimum reluctance occurs with minimum gap, hence the rotor points are attracted toward the stator magnet poles. Hybrid stepper motors are named because they use a combination of PM and VR techniques to achieve maximum power in a small package size.

Stepper BasicsControl of a stepper motor comes from applying a specific step sequence; rotational speed is controlled by the timing of the applied steps. The simplified diagrams below illustrate the effect of phase sequencing on rotational motion.

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Full step, low torque

Full Step, High Torque (standard application)

Half Step (best precision):

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How Stepper Motors Work

Stepper motors consist of a permanent magnet rotating shaft, called the rotor, and electromagnets on the stationary portion that surrounds the motor, called the stator. Figure 1 illustrates one complete rotation of a stepper motor. At position 1, we can see that the rotor is beginning at the upper electromagnet, which is currently active (has voltage applied to it). To move the rotor clockwise (CW), the upper electromagnet is deactivated and the right electromagnet is activated, causing the rotor to move 90 degrees CW, aligning itself with the active magnet. This process is repeated in the same manner at the south and west electromagnets until we once again reach the starting position.

Figure 1

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In the above example, we used a motor with a resolution of 90 degrees or demonstration purposes. In reality, this would not be a very practical motor for most applications. The average stepper motor's resolution -- the amount of degrees rotated per pulse -- is much higher than this. For example, a motor with a resolution of 5 degrees would move its rotor 5 degrees per step, thereby requiring 72 pulses (steps) to complete a full 360 degree rotation.

One may double the resolution of some motors by a process known as "half-stepping". Instead of switching the next electromagnet in the rotation on one at a time, with half stepping one needs to turn on both electromagnets, causing an equal attraction between, thereby doubling the resolution. As it can be seen in Figure 2, in the first position only the upper electromagnet is active, and the rotor is drawn completely to it. In position 2, both the top and right electromagnets are active, causing the rotor to position itself between the two active poles. Finally, in position 3, the top magnet is deactivated and the rotor is drawn all the way right. This process can then be repeated for the entire rotation.

Figure 2

There are several types of stepper motors. 4-wire stepper motors contain only two electromagnets, however the operation is more complicated than those with three or four magnets, because the driving circuit must BBDNITM, LKO 89

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be able to reverse the current after each step. For our purposes, we will be using a 6-wire motor.

Unlike these example motors which rotated 90 degrees per step, real-world motors employ a series of mini-poles on the stator and rotor to increase resolution. Although this may seem to add more complexity to the process of driving the motors, the operation is identical to the simple 90 degree motor we used in our example.

Stepper motor drive circuits

Stepper motor performance is strongly dependent on the drive circuit. Torque curves may be extended to greater speeds if the stator poles can be reversed more quickly, the limiting factor being the winding inductance. To overcome the inductance and switch the windings quickly, one must increase the drive voltage. This leads further to the necessity of limiting the current that these high voltages may otherwise induce.

L/R drive circuits

L/R drive circuits are also referred to as constant voltage drives because a constant positive or negative voltage is applied to each winding to set the step positions. However, it is winding current, not voltage that applies torque to the stepper motor shaft. The current I in each winding is related to the applied voltage V by the winding inductance L and the winding resistance R. The resistance R determines the maximum current according to Ohm's law I=U/R. The inductance L determines the maximum rate of change of the current in the winding according to the formula for an Inductor dI/dt = U/L. Thus when controlled by an L/R drive, the maximum speed of a stepper motor is limited by its inductance since

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at some speed, the voltage U will be changing faster than the current I can keep up.

With an L/R drive it is possible to control a low voltage resistive motor with a higher voltage drive simply by adding an external resistor in series with each winding. This will waste power in the resistors, and generate heat. It is therefore considered a low performing option, albeit simple and cheap.

Chopper drive circuits

Chopper drive circuits are also referred to as constant current drives because they generate a somewhat constant current in each winding rather than applying a constant voltage. On each new step, a very high voltage is applied to the winding initially. This causes the current in the winding to rise quickly since dI/dt = V/L where V is very large. The current in each winding is monitored by the controller, usually by measuring the voltage across a small sense resistor in series with each winding. When the current exceeds a specified current limit, the voltage is turned off or "chopped", typically using power transistors. When the winding current drops below the specified limit, the voltage is turned on again. In this way, the current is held relatively constant for a particular step position. This requires additional electronics to sense winding currents, and control the switching, but it allows stepper motors to be driven with higher torque at higher speeds than L/R drives. Integrated electronics for this purpose are widely available.

Phase current waveforms

A stepper motor is a polyphase AC synchronous motor (see Theory below), and it is ideally driven by sinusoidal current. A full step waveform BBDNITM, LKO 91

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is a gross approximation of a sinusoid, and is the reason why the motor exhibits so much vibration. Various drive techniques have been developed to better approximate a sinusoidal drive waveform: these are half stepping and microstepping.

Full step drive (two phases on)

This is the usual method for full step driving the motor. Both phases are always on. The motor will have full rated torque.

Wave drive

In this drive method only a single phase is activated at a time. It has the same number of steps as the full step drive, but the motor will have significantly less than rated torque. It is rarely used.

Half stepping

When half stepping, the drive alternates between two phases on and a single phase on. This increases the angular resolution, but the motor also has less torque at the half step position (where only a single phase is on). This may be mitigated by increasing the current in the active winding to compensate. The advantage of half stepping is that the drive electronics need not change to support it.

Microstepping

What is commonly referred to as microstepping is actual "sine cosine microstepping" in which the winding current approximates a sinusoidal AC waveform. Sine cosine microstepping is the most common form, but other waveforms are used [. Regardless of the waveform used, as the microsteps become smaller, motor operation becomes more smooth, BBDNITM, LKO 92

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thereby greatly reducing resonance in any parts the motor may be connected to, as well as the motor itself. It should be noted that while microstepping appears to make running at very high resolution possible, this resolution is rarely achievable in practice regardless of the controller, due to mechanical stiction and other sources of error between the specified and actual positions. In professional equipment gearheads are the preferred way to increase angular resolution.

Step size repeatability is an important step motor feature and a fundamental reason for their use in positioning. Example: many modern hybrid step motors are rated such that the travel of every Full step (example 1.8 Degrees per Full step or 200 Full steps per revolution) will be within 3% or 5% of the travel of every other Full step; as long as the motor is operated within its specified operating ranges. Several manufacturers show that their motors can easily maintain the 3% or 5% equality of step travel size as step size is reduced from Full stepping down to 1/10th stepping. Then, as the microstepping divisor number grows, step size repeatability degrades. At large step size reductions it is possible to issue many microstep commands before any motion occurs at all and then the motion can be a "jump" to a new position.

Applications

Computer-controlled stepper motors are one of the most versatile forms of positioning systems. They are typically digitally controlled as part of an open loop system, and are simpler and more rugged than closed loop servo systems.

Industrial applications are in high speed pick and place equipment and multi-axis machine CNC machines often directly driving lead screws or

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ballscrews. In the field of lasers and optics they are frequently used in precision positioning equipment such as linear actuators, linear stages, rotation stages, goniometers, and mirror mounts. Other uses are in packaging machinery, and positioning of valve pilot stages for fluid control systems.

Commercially, stepper motors are used in floppy disk drives, flatbed scanners, computer printers, plotters, slot machines, and many more devices.

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ACCESSORIES

VOLAGE REGULATOR Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or variable output voltages. The maximum current they can pass also rates them. Negative voltage regulators are available, mainly for use in dual supplies. Most regulators include some automatic protection from excessive current (over load protection) and overheating (thermal protection). Many of fixed voltage regulator ICs has 3 leads. They include a hole for attaching a heat sink if necessary.

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Power StageBill Of

Material(BOM)

1. IC 7805-----–----------1

2. 10uF (Electrolytic Capacitors )---------– 1

3. 1000uF(Electrolytic Capacitor)-------------1

4. 104 (.1uF) Ceramic Capacitor–-------------1

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DESCRIPTION These voltage regulators are monolithic circuit integrated circuit designed as fixed voltage regulators for a wide variety of applications including local, on card regulation. These regulators employ internal current limiting, therma safe-area compensation. With adequate heat sinking they can deliver output current in excess of 1.0 A. Although designed primarily as a fixed voltage regulator, these devices can be used with external components to obtain adjustable voltage and current.l shutdown, and safe-area compensation. With adequate heat sinking they can deliver output current in excess of 1.0 A. Although designed primarily as a fixed voltage regulator, these devices can be used with external components to obtain adjustable voltage and current.FEATURES

Output current in Excess of 1.0 A No external component required Internal thermal overload protection Internal short circuit current limiting Output transistor safe-area compensation Output voltage offered in 2% and 4% tolerance Available I n surface mount D2PAK and standard 3-lead transistor

packages

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Previous commercial temperature range has been extended

CAPACITORS

The capacitor's function is to store electricity, or electrical energy. The capacitor also functions as a filter, passing alternating current (AC), and blocking direct current (DC). This symbol is used to indicate a capacitor in a circuit diagram. The capacitor is constructed with two electrode plates facing each other but separated by an insulator.When DC voltage is applied to the capacitor, an electric charge is stored on each electrode. While the capacitor is charging up, current flows. The current will stop flowing when the capacitor has fully charged.Commercial capacitors are generally classified according to the dielectric. The most used are mica, paper, electrolytic and ceramic capacitors. Electrolytic capacitors use a molecular thin oxide film as the dielectric resulting in large capacitance values. There is no required polarity, since either side can be the most positive plate, except for electrolytic capacitors. These are marked to indicate which side must be positive to maintain the internal electrolytic action that produces the dielectric required to form the capacitance. It should be noted that the polarity of the charging source determines the polarity of the changing source determines the polarity of the capacitor voltage.

TYPES OF CAPACITORSThere are various types of capacitors available in the market.some of them are as follows:

Mica Capacitor Paper Capacitor Ceramic Capacitor

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Variable Capacitor Electrolytic Capacitor Tantalum Capacitor Film CapacitorHere we used only two types of capacitor i.e. ceramic capacitor & electrolytic capacitor.

CERAMIC CAPACITORThe ceramic dielectric materials are made from earth under extreme heat. By use of titanium dioxide or several types of silicates, very high values of dielectric constant can be obtained.

Ceramic capacitors

In the disk form, silver is fired onto both side of the ceramic, to form the conductor plates. For tabular ceramics, the hollow ceramic tube has a silver coating plates on the inside and outside surfaces. Temperature Coefficient is given in parts per million per degree Celsius with the reference of 25C. Ceramic capacitors are often used for the temperature compensation, to increase or decrease capacitance with the rise in the temperature.

ELECTROLYTIC CAPACITOR

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These capacitors are commonly used for capacitance values of 5 to 100 micro F, because they electrolytic provide the most capacitance in the smallest space with least cost. The construction consists of two metal electrodes, usually Aluminium, in an electrode of Borax, Phosphate or Carbonate. Between the two aluminium strips, absorbent gauze soaks up to provide the required electrolysis.

100uF/25V electrolytic capacitor

When the DC voltage is applied to form the capacitance during manufacture, the electrolytic action accumulates a molecular thin layer of aluminium oxide at the junction between the positive aluminium electrode and the electrolyte. Since the oxide is an insulator, there is capacitance between the positive aluminium electrode and the electrode in the gauze separator. The negative aluminium electrode simply provides a connection to the electrolyte. With the extremely thin dielectric film, very large capacitance values can be obtained. The area is increased by means of the long strips of aluminium foil and gauze, which are rolled into a compact cylinder having very high capacitance.Electrolytic capacitors are used in the circuits that have the combination of dc voltage and the ac voltage. The dc voltage maintains the polarity. A common application is for the electrolytic filter capacitors to eliminate the ac ripple in a dc power supply. If the electrolytic is connected in

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opposite polarity, the reversed electrolysis forms gas and the capacitor becomes hot and may explode. This possibility applies only to electrolytic capacitors. The disadvantage of electrolysis, in addition to the required polarization, is their relatively high leakage current, since the oxide film is not a perfect insulator. Non polarized electrolytic capacitors are also available for applications in ac circuits without any dc polarizing voltage. One use is for ac motors. A non polar electrolytic actually contains two capacitors, connected internally in series opposing polarity.

RESISTORSResistance is inserted into a circuit in order to reduce the current or to produce a desired IR voltage drop. The components for these uses, manufactured with the specific R, are resistors.The two main characteristics of a resistor are its R in ohms and the voltage rating. Resistors are available in a wide range of R values, from a fraction of ohm to many mega ohms. The power rating may be as high as several 100watts.

The power rating is important because it specifies the maximum wattage the resistance can dissipate without excessive heat. Wire wound resistors are used where the power dissipation is about 5 watts or more. For 2 watt or less, the carbon and wire wound resistors can be either fixed or variable. A fixed resistor has a specific R that cannot be adjusted. A variable resistor can be adjusted for any value between its 0ohms and its maximum R. An application for a variable wire wound resistor is to divide the voltage from a power supply. A carbon composition variable resistor is commonly used for control such as volume control in a radio. Hence there are many types of resistors some of them are :

Wire wound resistors Carbon composition resistors

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Carbon film resistors Metal film resistors Variable resistors

Resistors Colour Codes

Composition type resistors

Film type resistors

Note : bands "a" thru "d" are of equal width

Band: The first significant figure of the resistance value.BandB: The second significant value of the resistance value.BandC: The multiplier is the factor by which the two significant figures are multiplied to yield the nominal resistance value.BandD: The resistor’s toleranceBand E: When used on composition resistors, band E indicates the established reliability failure rate level. On film resistors, this band is BBDNITM, LKO 101

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approximately 1.5 times the width of the other bands, and indicates type of terminal.

RESISTOR NETWORKS:

Thick film resistor networks have a Metal Glaze Element on the ceramic substrates with a strong clip construction terminal and are coated with special epoxy resin. They are most suitable to meet the density of modern PCB layouts.

Schematics

Commoned:

1 2 3 4 5 6 7 8 n

Commoned parts are characterized by having a number of resisitive elements all of the same nominal value. All elements are connected to pin1

Isolated:

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Isolated parts are characterised by having number of resistive elements, all of the same nominal value.All elements are independent.

CRYSTAL OSCILLATOR

A crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. This frequency is commonly used to keep track of time (as in quartz wristwatches), to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits designed around them were called "crystal oscillators".

Picture of crystal oscillator

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A crystal oscillator is an electronic circuit that produces electrical oscillations at a particular designed frequency determined by the physical characteristics of one or more crystals, generally of quartz, positioned in the circuit feedback loop. A piezoelectric effect causes a crystal such as quartz to vibrate and resonate at a particular frequency. The quartz crystal naturally oscillates at a particular frequency, its fundamental frequency that can be hundreds of megahertz. The crystal oscillator is generally used in various forms such as a frequency generator, a frequency modulator and a frequency converter. The crystal oscillator utilizes crystal having excellent piezoelectric characteristics, in which crystal functions as a stable mechanical vibrator. There are many types of crystal oscillators. One of them is a crystal oscillator employing an inverting amplifier including a CMOS (complementary metal oxide semiconductor) circuit, and used, for example, as a reference signal source of a PLL (phase-pocked poop) circuit of a mobile phone. Crystal oscillator circuits using crystal have a number of advantages in actual application since crystals show high frequency stability and stable temperature characteristic as well as excellent processing ability. Temperature-compensated crystal oscillators, in which variation in oscillation frequency that arises from the frequency-temperature characteristic of the quartz-crystal unit is compensated, find particularly wide use in devices such as wireless phones used in a mobile environment. A surface mounting crystal oscillator is used mainly as a frequency reference source particularly for a variety of portable electronic devices such as portable telephones because of its compact size and light weight.

Commonly used crystal frequencies:

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Crystals can be manufactured for oscillation over a wide range of frequencies, from a few kilohertz up to several hundred megahertz. Many applications call for a crystal oscillator frequency conveniently related to some other desired frequency, so certain crystal frequencies are made in large quantities and stocked by electronics distributors.

Crystal oscillators of different frequencies along the uses

Frequency (MHz) 

Primary uses 

0.032768Real-time clocks, quartz watches and clocks; allows binary division to 1 Hz signal (215 × 1 Hz)

1.8432UART clock; allows integer division to common baud rates. (= 213 × 32 × 52. 16 × 115200 baud or 96 × 16 × 1200 baud)

2.4576UART clock; allows integer division to common baud rates up to 38400

3.2768Allows binary division to 100 Hz (32768 × 100 Hz, or 215 × 100 Hz)

3.575611 PAL M color subcarrier

3.579545NTSC M color subcarrier. Because these are very common and inexpensive they are used in many other applications, for example DTMF generators

3.582056 PAL N color subcarrier

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3.686400UART clock (2 × 1.8432 MHz); allows integer division to common baud rates

4.096000 Allows binary division to 1 kHz (212 × 1 kHz)

Crystal oscillator circuit used in microcontroller:A microcontroller is disclosed that includes a crystal oscillator circuit that is programmable to provide multiple different levels of startup current. In the present embodiment, the crystal oscillator circuit includes logic devices for receiving programming indicating one of a plurality of different startup current levels and a resistor chain. The logic devices are coupled to the resistor chain for controlling the resistance of the oscillator circuit such that, upon receiving programming indicating a particular startup current level, the crystal oscillator circuit generates a corresponding startup current. In addition, the crystal oscillator circuit includes provision for selecting one of a plurality of different levels of capacitance. Furthermore, the crystal oscillator circuit includes a pass gate that includes circuitry for assuring predetermined startup conditions are met. A feedback loop that includes an amplifier provides for steady-state operations that have low power consumption. DIODESA device having two terminals and has a low resistance to electrical current in one direction and a high resistance in the other direction. Diode is a two-element device which passes a signal in one direction only. They are used most commonly to convert AC to DC, because they pass the positive part of the wave, and block the negative part of the AC signal, or, if they are reversed, they pass only the negative part and not the positive part. Here we used only one type of diode:

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RECTIFICATION DIODE [1N4007]

The stripe stamped on one end of the diode shows indicates the polarity of the diode.The stripe shows the cathode side.The top two devices shown in the picture are diodes used for rectification. They are made to handle relatively high currents. The device on top can handle as high as 6A, and the one below it can safely handle up to 1A.However, it is best used at about 70% of its rating because this current value is a maximum rating.The third device from the top (red color) has a part number of 1S1588. This diode is used for switching, because it can switch on and off at very high speed. However, the maximum current it can handle is 120 mA. This makes it well suited to use within digital circuits. The maximum reverse voltage (reverse bias) this diode can handle is 30V.

The device at the bottom of the picture is a voltage regulation diode with a rating of 6V. When this type of diode is reverse biased, it will resist changes in voltage. If the input voltage is increased, the output voltage will not change. (Or any change will be an insignificant amount.) While the output voltage does not increase with an increase in input voltage, the output current will.

This requires some thought for a protection circuit so that too much current does not flow. The rated current limit for the device is 30 mA.

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Generally, a 3-terminal voltage regulator is used for the stabilization of a power supply. Therefore, this diode is typically used to protect the circuit from momentary voltage spikes. 3 terminal regulators use voltage regulation diodes inside.

FEATURES

Low forward voltage drop. Diffused Junction High Current Capability ROHS Compliant

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MICROSWITCH

In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another The most familiar form of switch is a manually operated electromechanical device with one or more sets of electrical contacts. Each set of contacts can be in one of two states: either 'closed' meaning the contacts are touching and electricity can flow between them, or 'open', meaning the contacts are separated and nonconducting.

A switch may be directly manipulated by a human as a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch. Automatically-operated switches can be used to control the motions of machines, for example, to indicate that a garage door has reached its full open position or that a machine tool is in a position to accept another workpiece. Switches may be operated by process variables such as pressure, temperature, flow, current, voltage, and force, acting as sensors in a process and used to automatically control a system. For example, a thermostat is an automatically-operated switch used to control a heating process. A switch that is operated by another electrical circuit is called a relay. Large switches may be remotely operated by a motor drive mechanism. Some switches are used to isolate electric power from a system, providing a visible point of isolation that can be pad-locked if necessary to prevent accidental operation of a machine during maintenance, or to prevent electric shock.

In the simplest case, a switch has two pieces of metal called contacts that touch to make a circuit, and separate to break the circuit. The contact material is chosen for its resistance to corrosion, because most metals form insulating oxides that would prevent the switch from

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working. Contact materials are also chosen on the basis of electrical conductivity, hardness (resistance to abrasive wear), mechanical strength, low cost and low toxicity

Sometimes the contacts are plated with noble metals. They may be designed to wipe against each other to clean off any contamination. Nonmetallic conductors, such as conductive plastic, are sometimes used.

MICRO SWITCH

A micro switch, also known as snap-action switch, is a generic term used to refer to an electric switch that is actuated by very little physical force, through the use of a tipping-point mechanism. They are very common due to their low cost and durability, greater than 1 million cycles and up to 10 million cycles for heavy duty models. This durability is a natural consequence of the design. Internally a stiff metal strip must be bent to activate the switch. This produces a very distinctive clicking sound and a very crisp feel. When pressure is removed the metal strip springs back to its original state. Common applications of micro switches include the door interlock on a microwave oven, levelling and safety switches in elevators, vending machines, and to detect paper jams or other faults in photocopiers. Micro switches are commonly used in tamper switches on gate valves on fire sprinkler systems and other water pipe systems, where it is necessary to know if a valve has been opened or shut.BBDNITM, LKO 110

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The defining feature of micro switches is that a relatively small movement at the actuator button produces a relative large movement at the electrical contacts, which occurs at high speed (regardless of the speed of actuation). Most successful designs also exhibit hysteresis, meaning that a small reversal of the actuator is insufficient to reverse the contacts; there must be a significant movement in the opposite direction. Both of these characteristics help to achieve a clean and reliable interruption to the switched circuit.

The first micro switch was invented by Peter McGall in 1932 in Freeport, Illinois. McGall was an employee of the Burgess Battery Company at the time. In 1937 he started the company MICRO SWITCH, which still exists as of 2009. The company and the Micro Switch trademark has been owned by Honeywell Sensing and Control since 1950. The trademark has become a widely used description for snap-action switches. Companies other than Honeywell now manufacture miniature snap-action switches.

Micro switches are applied in appliances, machinery, industrial controls, vehicles, and many other places for control of electrical circuits. Micro switches are usually rated to carry current in control circuits only, although some switches can be directly used to control small motors, solenoids, lamps, or other devices. Micro switches may be directly operated by a mechanism, or may be packaged as part of a pressure, BBDNITM, LKO 111

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flow, or temperature switch, operated by a sensing mechanism such as a Bourdon tube. A motor driven cam and one or more micro switches form a timer mechanism. The snap-switch mechanism can be enclosed in a metal housing including actuating levers, plungers or rollers, forming a limit switch useful for control of machine tools or electrically-driven machinery.

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PCB-DESIGNING

PCB Designing includes the following steps:-

1.Processing

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CLEANSING

ETCHING

DRILLING

SOLDERING

MASKING

PROCESSING

PRINTING

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The layout of a PCB has to incorporate all the information on the board before one can go on to the artwork preparation. This means that a concept that clearly defines all the details of the circuit and partly also of the final equipment, is a prerequisite before the actual layout can start. The detail circuit diagram is very important for the layout designer and he must also be familiar with the design concept and with the philosophy behind the equipment. The General Considerations are- a-) Layout scale:- Depending on the accuracy required, artwork should be produced at a 1:1 or 2:1 or even 4:1 scale. The layout is best prepared on the same scale as the artwork. This prevents all the problems which might be caused by redrawing of layout to the artwork scale.b-) Grid system or Graph Paper: - It is commonly accepted practice to use these for designing.c-) Board types:-There are two side of a PCB board – Component side & Solder side. Depending on these board are classified as-

Single-sided Boards: - These are used where costs have to be kept at a minimum & a particular Circuit can be accommodated on such board. To jump over conductor tracks, components have to be utilized. If this is not feasible, jumper wires are used. (Jumper wires should be less otherwise double-sided PCB should be considered.

Double-sided Boards: - These are made with or without plated through holes. Plated through holes are fairly expensive.

2. CleaningThe cleaning of the copper surface prior to resist application is an

essential step for any type of PCB process using etches or plating resist. After scrubbing with the abrasive, a water rinse will remove most of

the remaining slurry.

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Scrubbing

Water Rinse

Wet Brushing

Acid dip

Final Rinse

Drying

Pumice/ Acid Slurry

Tap Water

Tap Water

Hydrochloric Acid-HCl

De-ionized Water

Oven or Blowing of air.

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3. EtchingIt is of utmost importance to choose a suitable Etchant Systems. There are many factors to be considered:-

Etching speed Copper solving capacity Etchant price Pollution character

Operation characteristics of different etchants:-Factor Etchant

Corrosive-ness

Neutralization disposition problem

Toxicity

Required ventilation

Operation cost

FeCl3 High Medium Low Low MediumCuCl2 High Low Mediu

mMedium Low

Chromic acid

High High High High High

Alkaline High Medium Mediu High HighBBDNITM, LKO 115

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ammonia

m

Table: Characteristics of different etchantsWe have uses FeCl3 (Conc. 120 g/litre 0.1 M) for etching.

Reactions Involved:-FeCl3 + 3H 2O Fe(OH)3 + 3HCl (Free acid attack to copper) FeCl3 + Cu FeCl2 + CuCl FeCl3 + CuCl FeCl2 + CuCl2CuCl2 + Cu 2CuCl

4.DRILLING The importance of hole drilling into PCB’s has further gone with electronic component miniaturization and its need for smaller holes diameters (diameters less than half the board thickness) and higher package density.

The following hole diameter tolerances have been generally accepted wherever no other specifications are mentioned.Hole Diameter (D) <= 1mm + / - 0.05 mmHole Diameter (D) > 3 mm + / – 0.1 mm Drill bits are made up of high-speed steel (HSS), Glass epoxy material, Tungsten Carbide.

5. SOLDERINGFlux should be removed after Soldering. It is done through washing

by 0.5—1 % HCl followed by Neutralization in dilute alkali to remove corrosive flux.Non-corrosive is removed by Iso-Propanal.6. MASKING

It is done for the protection of conductor track from Oxidation.

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DESIGNING OF PCB LAYOUTA PCB layout is required to place components on the PCB so that

the component area can be minimized and the components can be placed in an efficient manner. The components can be placed in two ways, either manually or by software. The manual procedure is quiet cumbersome and is very inefficient. The other method is by the use of computer software. This method is advantageous as it saves time and valuable copper area. There are various software’s available for this purpose like-

Express PCB Pad2pad Protel PCB PCB design e.t.c.

Many of them are loaded with auto routing and auto placement facility. The software that we have used here is EXPRESS PCB. This software has a good interface, easy editing options and a wide range of components. Express P.C.B.

Express PCB is a very easy to use Windows application for laying out printed circuit boards. There are two parts to Express PCB, Express SCH for drawing schematics and Express PCB for designing circuit boards. We downloaded the software from the website www.expresspcb.com. There are lots of functions available in the software. This software is free of cast and also it is very easy to use. The different layers of the PCB can be viewed by just a click of a button on the interface. And we easily get its print on paper which is utilized for further processing. We can design single sided PCB as well as Double Sided PCB with this Software

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SOURCE CODE

MIKRO C CODE:void main() {while (1) { if ((P3_4==0)&&(P3_5==1)&&(P3_6==0)&&(P3_7==0)) //button 2 { P0_0=1; P0_1=0; P0_2=1; P0_3=0; } if ((P3_4==0)&&(P3_5==0)&&(P3_6==0)&&(P3_7==1)) //button 8 { P0_0=0; P0_1=1; P0_2=0; P0_3=1; } if ((P3_4==0)&&(P3_5==0)&&(P3_6==1)&&(P3_7==0)) //button 4 { P0_0=0; P0_1=1; P0_2=1; P0_3=0; } if ((P3_4==0)&&(P3_5==1)&&(P3_6==1)&&(P3_7==0)) //button 6 { P0_0=1; P0_1=0; P0_2=0; P0_3=1; } if ((P3_4==1)&&(P3_5==0)&&(P3_6==0)&&(P3_7==0)) //button 1 { P0_4=1; Delay_ms(40); P0_4=0; P0_5=1; Delay_ms(40); P0_5=0; P0_6=1;

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Delay_ms(40); P0_6=0; P0_7=1; Delay_ms(40); P0_7=0; } if ((P3_4==1)&&(P3_5==1)&&(P3_6==0)&&(P3_7==0)) //button 3 { P0_4=1; Delay_ms(40); P0_4=0; P0_7=1; Delay_ms(40); P0_7=0; P0_6=1; Delay_ms(40); P0_6=0; P0_5=1; Delay_ms(40); P0_5=0; }

if ((P3_4==1)&&(P3_5==1)&&(P3_6==1)&&(P3_7==0)) //button 7 { if (P1_0==1) { P0_0=0; P0_1=1; P0_2=1; P0_3=0; } if (P1_0==0) { P0_0=1; P0_1=0; P0_2=1; P0_3=0; } } if ((P3_4==1)&&(P3_5==0)&&(P3_6==1)&&(P3_7==0)) {

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P0=0x00; } }}

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BIBLIOGRAPHY

http://www.atmel.com/dyn/resources/prod_documents/doc3286.pdfhttp://www.botskool.com/downloads/electronics/datasheets/HT12D.pdfhttp://www.ipic.co.jp/Pdffiles/ht12e.pdfhttp://www.datasheetcatalog.org/datasheets/228/390068_DS.pdfhttp://www.datasheetcatalog.org/datasheet/texasinstruments/l293d.pdfhttp://www.national.com/ds/LM/LM124.pdfhttp://en.wikipedia.org/wiki/Ultrasonic_sensorhttp://www.vegakitindia.com/productdetails.asp?ProdID=RF01B433http://www.rapidonline.com/netalogue/specs/63-0010e.pdf http://en.wikipedia.org/wiki/Stepper_motor

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