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Description of Components

1. 8051 Microcontroller :

The Intel 8051 is a single chip microcontroller (C) . Intel's original 8051 family wasdeveloped using NMOS technology, but later versions, identified by a letter "C" in theirname, e.g. 80C51, used CMOS technology and were less power-hungry than their NMOSpredecessors - this made them eminently more suitable for battery-powered devices. Aparticularly useful feature of the 8051 core is the inclusion of a Boolean processingengine which allows bit-level Boolean logic operations to be carried out directly andefficiently on internal registers and RAM. This feature helped to cement the 8051'spopularity in industrial control applications. Another valued feature is that it has fourseparate register sets, which can be used to greatly reduce interrupt latency compared tothe more common method of storing interrupt context on a stack. 8051 based

microcontrollers typically include one or two UARTs, two or three timers, 128 or 256bytes of internal data RAM (16 bytes of which are bit-addressable), up to 128 bytes ofI/O, 512 bytes to 64 kB of internal program memory, and sometimes a quantity ofextended data RAM (ERAM) located in the external data space.

Important features of 8051

1. It provides many functions (CPU, RAM, ROM, I/O, interrupt logic, timer, etc.) ina single package

2. 8-bit data bus - It can access 8 bits of data in one operation (hence it is an 8-bitmicrocontroller)

3. 16-bit address bus - It can access 216 memory locations - 64 kB each of RAM andROM
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4. On-chip RAM - 128bytes ("Data Memory")

5. On-chip ROM - 4 kB ("Program Memory")

6. Four byte bi-directional input/output port

7. UART (serial port)

8. Two 16-bit Counter/timers

8. Two-level interrupt priority

10. Power saving mode

. LCD (16X2 Lines)

The 2 line x 16 character LCD modules are available from awide range of manufacturers.

LCDs have become very popular over recent years forinformation display in many smart appliances. They areusually controlled by microcontrollers. They make complicatedequipment easier to operate.
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LCDs come in many shapes and sizes but the most common isthe 16 character x 2 line display with no back light. It requiresonly 11 connections eight bits for data (which can bereduced to four if necessary) and three control lines (we have

only used two here). It runs off a 5V DC supply and only needsabout 1mA of current. The display contrast can be varied bychanging the voltage into pin 3 of the display, usually with atrimpot.

4. IR Transmitter & Receiver:

Several motherboards have the necessary hardware for theinstallation of an infrared transmitter/receiver, requiring onlythe installation of a module containing the infrared sensor. Thegreat problem, however, is that this module is not easily foundin the market and, when it is, its price is high.

IR LED is being driven by a 38 KHz oscillator. The oscillator isusing a IC 555 timer to generate the square waveform. IC555is very robust and easily available IC. The Frequency

generated by 555 is adjustable and can be fine tuned to matchwith receiver.


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2. Voltage Regulator (7805)

Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or

Voltage regulatorPhotograph

variable output voltages. They are also rated by the maximum current they canpass. Negative voltage regulators are available, mainly for use in dual supplies.Most regulators include some automatic protection from excessive current('overload protection') and overheating ('thermal protection').

Many of the fixed voltage regulator ICs have 3 leads and look like powertransistors, such as the 7805 +5V 1A regulator shown on the right. They include

a hole for attaching a heatsink if necessary.

Features :
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1. Internal thermal overload protection2. No external components required3. Output transistor safe area protection4. Internal short circuit current limit

Voltage :

1. 7805..5V2. 7812.12V3. 7815.15V

3. D.C. motor :-

An electric motor is a machine which converts electrical energy into mechanical energy.


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Principle:

It is based on the principle that when a current-carrying conductor is placed in a

magnetic field, it experiences a mechanical force whose direction is given by Fleming'sLeft-hand rule and whose magnitude is given by

Force, F = B I l newton

Where B is the magnetic field in weber/m2.

I is the current in amperes and

l is the length of the coil in meter.

The force, current and the magnetic field are all in different directions.

If an Electric current flows through two copper wires that are between the poles of amagnet, an upward force will move one wire up and a downward force will move theother wire down.

Figure 1: Force in DC Motor
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Figure 2 : Magnetic Field in DC Motor

Figure 3 : Torque in DC Motor

Figure 4 : Current Flow in DC Motor

The loop can be made to spin by fixing a half circle of copper which is known ascommutator, to each end of the loop. Current is passed into and out of the loop bybrushes that press onto the strips. Thebrushes do not go round so the wire do not gettwisted. This arrangement also makes sure that the current always passes down on theright and back on the left so that the rotation continues. This is how a simple Electricmotor is made.
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The Stepper Motor

The stepper motor operation is directly related to the following points:

The motors rotation has several direct relationships to the applied pulses.

The sequence of applied pulses is directly related to the direction of motor shaft

rotation.

The speed of the motor shaft rotation is directly related to the frequency of the

input pulses.

The length of rotation is directly related to the number of input pulses applied.

The motor operates whenever command is given from the computer. It is a four-phase

DC motor. When the command for rotating right or left is given, the micro controller

supplies power to each of the four winding sequentially in steps. Thus, the motor rotatesaccordingly. However, the output of the micro controller is only +5 Volts. Which is not

sufficient to drive the motor. This needs to be amplified to make it useful for the motor.

That is why, the signal is first passed through a driver circuit (NPN General Purpose

Amplifier 845c). The voltage gain of this driver circuit is unity, but the current gain is

times for each transistor. Now, this current amplified signal is made to pass through a


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power circuit (407), where it is voltage amplified and made influential enough to operate

the stepper motor. since, the stepper motor has four windings, and each winding needs to

be controlled individually, the controller sends signal for each winding through a separate

pin and therefore, each signal is provided with a separate pair of driver and power circuit.

A major question arising is why the use of stepper motor and not the servo motor, since,

the servomotor has the distinct advantage of operating both in AC and DC. Well,

following are the advantages of the stepper motor:

The rotation angle of the motor is proportional to the input pulse.

The motor has full torque at standstill (if the windings are energized).

Precise positioning and repeatability of movement since good stepper motors have

an accuracy of 3 - 5% of a step and this error is non cumulative from one step to

the next.

Excellent response to starting/stopping/reversing.


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Very reliable since there are no contact brushes in the motor. Therefore the life of

the motor is simply dependant on the life of the bearing.

The motors response to digital input pulses provides open-loop control, making

the motor simpler and less costly to control.

It is possible to achieve very low speed synchronous rotation with a load that is

directly coupled to the shaft.

A wide range of rotational speeds can be realized, as the speed is proportional to

the frequency of the input pulses.

Less cost.

Degree of rotation is a function of their construction and therefore consistent.

No feedback is necessary for positional or speed control.


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Any errors present are non-cumulative.

Still however, the choice between the two depends on the application for which they arebeing used. But the economical operation of the stepper motor makes it a synthesisersfirst choice.

Four phase stepper motor operating circuit


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Stepper Motor Controlling Circuit

An operational amplifier, which is often called an op-amp, is a DC-coupled high-gainelectronic voltageamplifierwith differential inputs and, usually, a single output.[1]

Typically the output of the op-amp is controlled either bynegative feedback, whichlargely determines the magnitude of its output voltage gain, or bypositive feedback,

which facilitates regenerative gain and oscillation. High input impedance at the inputterminals (ideally infinite) and low output impedance (ideally zero) are important typicalcharacteristics.

Op-amps are among the most widely used electronic devices today, being used in a vastarray of consumer, industrial, and scientific devices. Many standard IC op-amps cost onlya few cents in moderate production volume; however some integrated or hybridoperational amplifiers with special performance specifications may cost over $100 US insmall quantities.

Modern designs are electronically more rugged than earlier implementations and some

can sustain direct short circuits on their outputs without damage.

The op-amp is one type ofdifferential amplifier. Other types of differential amplifierinclude the fully differential amplifier(similar to the op-amp, but with 2 outputs), theinstrumentation amplifier(usually built from 3 op-amps), the isolation amplifier(similarto the instrumentation amplifier, but which works fine with common-mode voltages thatwould destroy an ordinary op-amp), and negative feedback amplifier(usually built from1 or more op-amps and a resistive feedback network).

[edit] Applications

DIPpinout for 741-type operational amplifier
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Main article: Operational amplifier applications

[edit] Use in electronics system design

The use of op-amps as circuit blocks is much easier and clearer than specifying all their

individual circuit elements (transistors, resistors, etc.), whether the amplifiers used areintegrated or discrete. In the first approximation op-amps can be used as if they wereideal differential gain blocks; at a later stage limits can be placed on the acceptable rangeof parameters for each op-amp.

Circuit design follows the same lines for all electronic circuits. A specification is drawnup governing what the circuit is required to do, with allowable limits. For example, thegain may be required to be 100 times, with a tolerance of 5% but drift of less than 1% ina specified temperature range; the input impedance not less than 1 megohm; etc.

A basic circuit is designed, often with the help of circuit modeling (on a computer).

Specific commercially available op-amps and other components are then chosen thatmeet the design criteria within the specified tolerances at acceptable cost. If not allcriteria can be met, the specification may need to be modified.

A prototype is then built and tested; changes to meet or improve the specification, alterfunctionality, or reduce the cost, may be made.

[edit] Positive feedback configurations

Another typical configuration of op-amps is the positive feedback, which takes a fractionof the output signal back to the non-inverting input. An important application of it is the

comparator with hysteresis (i.e., theSchmitt trigger).

[edit] Basic single stage amplifiers

[edit] Non-inverting amplifier

An op-amp connected in the non-inverting amplifier configuration

The general op-amp has two inputs and one output. The output voltage is a multiple ofthe difference between the two inputs (some are made with floating, differentialoutputs):
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G is the open-loop gain of the op-amp. The inputs are assumed to have very highimpedance; negligiblecurrent will flow into or out of the inputs. Op-amp outputs havevery lowsource impedance.

If the output is connected to the inverting input, after being scaled by a voltage divider:

then:

, where G> 0

Solving forVout/ Vin, we see that the result is a linear amplifier with gain:

IfG is very large, comes close to .

[edit] Inverting amplifier

Because it does not require a differential input, this negative feedback connection was themost typical use of an op-amp in the days ofanalog computers.[citation needed] It remains verypopular,[citation needed] but many different configurations are possible, making it one of themost versatile of all electronic building blocks.
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An op-amp connected in the inverting amplifier configuration

By applying KCL at the inverting input,

However, because the input current into any operational amplifier is assumed to be zero,

and so

By applying KVL at the output,

However, because the operational amplifier is in a negative-feedback configuration, the

inverting input v can be assumed to match the non-inverting input v+ . In particular,

and so v is a virtual ground. Therefore,

Hence, closed loop gain [6]

Some Variations:o A resistor is often inserted between the non-inverting input and ground (so

both inputs "see" similar resistances), reducing the input offset voltage dueto different voltage drops due tobias current, and may reduce distortion insome op-amps.

o A DC-blockingcapacitormay be inserted in series with the input resistor

when a frequency responsedown to DC is not needed and any DC voltageon the input is unwanted. That is, the capacitive component of the inputimpedance inserts a DC zero and a low-frequencypolethat gives thecircuit abandpass orhigh-pass characteristic.

[edit] Circuit notation
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Circuit diagram symbol for an op-amp

The circuit symbol for an op-amp is shown to the right, where:

V+ : non-inverting input

V : inverting input

Vout: output VS+ : positive power supply VS : negative power supply

The power supply pins (VS+ and VS ) can be labeled in different ways (See IC powersupply pins). Despite different labeling, the function remains the same to provideadditional power for amplification of signal. Often these pins are left out of the diagramfor clarity, and the power configuration is described or assumed from the circuit.

[edit] Operation

The amplifier's differential inputs consist ofV+ input and a V input, and generally theop-amp amplifies only the difference in voltage between the two. This is called thedifferential input voltage. Operational amplifiers are usually used with feedback loopswhere the output of the amplifier would influence one of its inputs. The output voltageand the input voltage it influences settles down to a stable voltage after being connectedfor some time, when they satisfy the internal circuit of the op amp.

In its most common use, the op-amp's output voltage is controlled by feeding a fractionof the output signal back to the inverting input. This is known asnegative feedback. Ifthat fraction is zero (i.e., there is no negative feedback) the amplifier is said to be runningopen loop and its output is the differential input voltage multiplied by the total gain of the

amplifier, as shown by the following equation:

where V+ is the voltage at the non-inverting terminal, V is the voltage at the invertingterminal and G is the total open-loop gain of the amplifier.
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Since the magnitude of the open-loop gain is typically very large, open-loop operationresults in op-amp saturation (see below inNonlinear imperfections) unless the differentialinput voltage is extremely small. Finley's law states that "When the inverting and non-inverting inputs of an op-amp are not equal, its output is in saturation." Additionally, theprecise magnitude of this gain is not well controlled by the manufacturing process, and so

it is impractical to use an operational amplifier as a stand-alone differential amplifier.Instead, op-amps are usually used innegative-feedbackconfigurations.

Most single, dual and quad op-amps available have a standardized pin-out which permitsone type to be substituted for another without wiring changes. A specific op-amp may bechosen for its open loop gain, bandwidth, noise performance, input impedance, powerconsumption, or a compromise between any of these factors.

[edit] Ideal op-amp

Equivalent circuit of an operational amplifier.

Shown on the right is an example of an ideal operational amplifier. The main part in anamplifier is the dependent voltage source that increases in relation to the voltage drop

acrossRin, thus amplifying the voltage difference between V+ and V . Many uses havebeen found for operational amplifiers and an ideal op-amp seeks to characterize thephysical phenomena that make op-amps useful.

Supply voltages Vcc+ and Vcc are used internally to implement the dependent voltagesources. The positive source Vs+ acts as an upper bound on the output, and the negativesource Vs acts as a lower bound on the output. The internalVs+ and Vs connectionsare not shown here and will vary by implementation of the operational amplifier.

For any input voltages, an idealop-amp has the following properties:
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Infinite open-loop gain (i.e., when doing theoretical analysis, limit should be

taken as open loop gain Gopenloop goes to infinity) Infinitebandwidth (i.e., the frequency magnitude response is flat everywhere with

zerophase shift).

Infinite input impedance (i.e., , and so zero current flows from V+ to

V ) Zero input current (i.e., there is no leakage orbias current into the device)

Zero input offset voltage (i.e., when the input terminals are shorted so that V+ =V , the output is avirtual ground).

Infinite slew rate (i.e., the rate of change of the output voltage is unbounded) andpower bandwidth (full output voltage and current available at all frequencies).

Zero output impedance(i.e.,Rout= 0, and so output voltage does not vary withoutput current)

Zero noise Infinite Common-mode rejection ratio (CMRR)

Infinite Power supply rejection ratio for both power supply rails.

Because of these properties, an op-amp can be modeled as a nullor.

The 555 Timer IC is an integrated circuit (chip) implementing a variety oftimerandmultivibratorapplications. The IC was designed and invented by Hans R. Camenzind. Itwas designed in 1970 and introduced in 1971 by Signetics (later acquired by Philips).The original name was the SE555/NE555 and was called "The IC Time Machine".[1] The555 gets its name from the three 5-kohm resistors used in typical early implementations.[2] It is still in wide use, thanks to its ease of use, low price and good stability. As of2003[update], 1 billion units are manufactured every year.[citation needed]

Depending on the manufacturer, it includes over 20 transistors, 2diodes and 15 resistorson a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8).[3]

The 556 is a 14-pin DIP that combines two 555s on a single chip.

The 558 is a 16-pin DIP that combines four slightly modified 555s on a single chip (DIS& THR are connected internally, TR is falling edge sensitive instead of level sensitive).

Also available are ultra-low power versions of the 555 such as the 7555 and TLC555.[4]

The 7555 requires slightly different wiring using fewer external components and less

power.

The 555 has three operating modes:

Monostable mode: in this mode, the 555 functions as a "one-shot". Applicationsinclude timers, missing pulse detection, bouncefree switches, touch switches,frequency divider, capacitance measurement, pulse-width modulation (PWM) etc
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Astable - free running mode: the 555 can operate as anoscillator. Uses includeLED and lamp flashers, pulse generation, logic clocks, tone generation, securityalarms,pulse position modulation, etc.

Bistable mode orSchmitt trigger: the 555 can operate as aflip-flop, if the DIS pinis not connected and no capacitor is used. Uses include bouncefree latched

switches, etc.

NE555 from Signetics in dual-in-line package

Internal schematics

[edit] Usage

Schematic symbol
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The connection of the pins is as follows:

Nr

.Name Purpose

1 GND Ground, low level (0V)

2 TR A short pulse high low on the trigger starts the timer

3 Q During a timing interval, the output stays at+VCC

4 R A timing interval can be interrupted by applying a reset pulse to low (0V)

5 CV Control voltage allows access to the internal voltage divider (2/3 VCC)

6 THR The threshold at which the interval ends (it ends if U.thr 2/3 VCC)

7 DIS Connected to a capacitor whose discharge time will influence the timing interval

8 V+, VCC The positive supply voltage which must be between 3 and 15 V

Schematic of a 555 in monostable mode[edit] Monostable mode

In the monostable mode, the 555 timer acts as a one-shot pulse generator. The pulsebegins when the 555 timer receives a trigger signal. The width of the pulse is determinedby the time constant of an RC network, which consists of a capacitor(C) and a resistor(R). The pulse ends when the charge on the C equals 2/3 of the supply voltage. The pulse
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width can be lengthened or shortened to the need of the specific application by adjustingthe values of R and C.[5]

The pulse width of time tis given by

which is the time it takes to charge C to 2/3 of the supply voltage. See RC circuit for anexplanation of this effect.

The relationships of the trigger signal, the voltage on the C and the pulse width are shownbelow:

Diagram of waveforms of 555 in monostable mode

[edit] Astable mode

Standard 555 Astable Circuit

In astable mode, the '555 timer' outputs a continuous stream of rectangular pulses havinga specified frequency. A resistor (call it R1) is connected between Vcc and the dischargepin (pin 7) and another (R2) is connected between the discharge pin (pin 7) and thetrigger (pin 2) and threshold (pin 6) pins that share a common node. Hence the capacitor
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is charged through R1 and R2, and discharged only through R2, since pin 7 has lowimpedance to ground during output low intervals of the cycle, therefore discharging thecapacitor. The use of R2 is mandatory, since without it the high current spikes from thecapacitor may damage the internal discharge transistor.

In the astable mode, the frequency of the pulse stream depends on the values of R1, R2and C:

[6]

The high time from each pulse is given by

and the low time from each pulse is given by

where R1 and R2 are the values of the resistors inohms and C is the value of thecapacitor in farads.

[edit] Specifications

These specifications apply to the NE555. Other 555 timers can have better specificationsdepending on the grade (military, medical, etc).

Supply voltage (VCC) 4.5 to 15 V

Supply current (VCC = +5 V) 3 to 6 mA

Supply current (VCC = +15 V) 10 to 15 mA

Output current (maximum) 200 mA

Power dissipation 600 mW

Operating temperature 0 to 70 C

ADC0801/ADC0802/ADC0803/ADC0804/ADC0805
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8-Bit P Compatible A/D Converters

ADC0804

General Description

The ADC0801, ADC0802, ADC0803, ADC0804 and ADC0805 are CMOS 8-bitsuccessive approximation A/D converters that use a differential potentiometric laddersimilar to the 256R products. These converters are designed to allow operation with theNSC800 and INS8080Aderivative control bus with TRI-STATE output latches directlydriving the data bus. These A/Ds appear like memory locationsor I/O ports to themicroprocessor and no interfacing logic is needed. Differential analog voltage inputsallow increasing the common-mode rejection and offsetting the analog zero input voltagevalue. In addition, the voltage reference input can be adjusted to allow encoding anysmaller analog voltage span to the full 8 bits of resolution.

Features

Compatible with 8080 P derivativesno interfacing logic needed - access time -

135 ns

Easy interface to all microprocessors, or operates stand alone

Differential analog voltage inputs

Logic inputs and outputs meet both MOS and TTL voltage level specifications

Works with 2.5V (LM336) voltage reference

On-chip clock generator

0V to 5V analog input voltage range with single 5V supply

No zero adjust required


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0.3" standard width 20-pin DIP package

20-pin moulded chip carrier or small outline package

Operates ratio metrically or with 5 VDC, 2.5 VDC, or analog span adjusted voltage

reference

Key Specifications

Resolution 8 bits

Total error 1/4 LSB, 1/2 LSB and 1 LSB

Conversion time 100 s

Connection Diagram


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4. Max 232:-

Now that we have the 8 bit value in the 8051, we want to send that value to the PC. The8051 has a built in serial port that makes it very easy to communicate with the PC's serialport but the 8051 outputs are 0 and 5 volts and we need +10 and -10 volts to meet theRS232 serial port standard. The easiest way to get these values is to use the MAX232.The MAX232 acts as a buffer driver for the processor. It accepts the standard digital logicvalues of 0 and 5 volts and converts them to the RS232 standard of +10 and -10 volts. It


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also helps protect the processor from possible damage from static that may come frompeople handling the serial port connectors.

The MAX232 requires 5 external 1uF capacitors. These are used by the internal chargepump to create +10 volts and -10 volts.

For the first capacitor, the negative leg goes to ground and the positive leg goes to pin 16.

For the second capacitor, the negative leg goes to 5 volts and the positive leg goes to pin2.

For the third capacitor, the negative leg goes to pin 3 and the positive leg goes to pin 1.

For the fourth capacitor, the negative leg goes to pin 5 and the positive leg goes to pin 4.

For the fifth capacitor, the negative leg goes to pin 6 and the positive leg goes to ground.

The MAX232 includes 2 receivers and 2 transmiters so two serial ports can be used witha single chip. We will only use one transmiter for this project. The only connection thatmust be made to the 2051 is one jumper from pin 3 of the 2051 to pin 11 of the MAX232.

To power the MAX232 :

Connect pin 16 to 5 volts.Connect pin 15 to ground.

The only thing left is that we need some sort of connector to connect to the serial port.The sample code below is written for Comm1 and most computers use a 9 pin DB9 maleconnector for Comm1 so a 9 pin female connector is included for this project. You mayalso want to buy a DB9 extension cable (Shown on order form as DB9 to DB9 cable) tomake the connection easier. There should be 3 wires soldered to the DB9 connector pins2, 3 and 5. Connect the wire from pin 5 of the connector to ground on the breadboard.Connect the wire from pin 2 of the connector to pin 14 of the MAX232. (The other wireis for receiveing and is not used in this project.)


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5 . Proximity Sensor :-

Proximity sensors are sensors able to detect the presence of nearby objects without anyphysical contact. A proximity sensor often emits an electromagnetic or electrostatic field,

or a beam of electromagnetic radiation (infrared, for instance), and looks for changes inthe field or return signal. The object being sensed is often referred to as the proximitysensor's target. Different proximity sensor targets demand different sensors. For example,a capacitive or photoelectric sensor might be suitable for a plastic target; an inductiveproximity sensor requires a metal target.The maximum distance that this sensor candetect is defined "nominal range". Some sensors have adjustments of the nominal rangeor means to report a graduated detection distance.

Proximity sensors can have a high reliability and long functional life because of theabsence of mechanical parts and lack of physical contact between sensor and the sensedobject. A proximity sensor adjusted to a very short range is often used as a touch switch.
http://en.wikipedia.org/wiki/Sensorhttp://en.wikipedia.org/wiki/Touch_switchhttp://en.wikipedia.org/wiki/Sensorhttp://en.wikipedia.org/wiki/Touch_switch


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6. RELAY :-

A relay is really a remotely controlled switch. In the diagram above, a power circuitcontains a switch which is opened and closed by operation of a relay. The relay is

activated by a magnetic core which is energised when a controlling switch is closed. Asthe core is energised, it lifts and closes a pair of contacts in a second circuit - usually apower circuit. The current required for the relay is usually much lower than that used forthe power circuit so it can be provided by a battery.

7. TRANSISTORS:-

In electronics, a transistor is a semiconductor device commonly used to amplify orswitch electronic signals. A transistor is made of a solid piece of a semiconductormaterial, with at least three terminals for connection to an external circuit. A voltage or
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current applied to one pair of the transistor's terminals changes the current flowingthrough another pair of terminals. Because the controlled (output) powercan be muchlarger than the controlling (input) power, the transistor provides amplification of a signal.The transistor is the fundamental building block of modern electronic devices, and is usedin radio, telephone, computerand other electronic systems. Some transistors are packaged

individually but most are found in integrated circuits.

Usage

Thebipolar junction transistor, or BJT, was the first transistor invented, and through the1970s, was the most commonly used transistor. Even afterMOSFETs became available,the BJT remained the transistor of choice for many analog circuits such as simpleamplifiers because of their greater linearity and ease of manufacture. Desirable propertiesof MOSFETs, such as their utility in low-power devices, usually in the CMOSconfiguration, allowed them to capture nearly all market share for digital circuits; morerecently MOSFETs have captured most analog and power applications as well, includingmodern clocked analog circuits, voltage regulators, amplifiers, power transmitters, motordrivers, etc.

BJT used as an electronic switch,

In grounded-emitter configuration.Simplified operation

The essential usefulness of a transistor comes from its ability to use a small signal appliedbetween one pair of its terminals to control a much larger signal at another pair ofterminals. This property is called gain. A transistor can control its output in proportion tothe input signal, that is, can act as an amplifier. Or, the transistor can be used to turncurrent on or off in a circuit like an electrically controlled switch, where the amount ofcurrent is determined by other circuit elements.The two types of transistors have slight

differences in how they are used in a circuit. A bipolar transistor has terminals labelledbase, collector and emitter. A small current at base terminal (that is, flowing from thebase to the emitter) can control or switch a much larger current between collector andemitter terminals. For a field-effect transistor, the terminals are labelled gate, source, anddrain, and a voltage at the gate can control a current between source and drain.

The image to the right represents a typical bipolar transistor in a circuit. Charge will flowbetween emitter and collector terminals depending on the current in the base. Since
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internally the base and emitter connections behave like a semiconductor diode, a voltagedrop develops between base and emitter while the base current exists. The size of thisvoltage depends on the material the transistor is made from, and is referred to as VBE.

Simple circuit using a transistor Operation graph of a transistor

Transistor as an amplifier

Amplifier circuit, standard

common-emitter configuration.

The above common emitter amplifier is designed so that a small change in voltage in (Vin)changes the small current through the base of the transistor and the transistor's currentamplification combined with the properties of the circuit mean that small swings in Vinproduce large changes in Vout.

It is important that the operating parameters of the transistor are chosen and the circuitdesigned such that as far as possible the transistor operates within a linearportion of thegraph, such as that shown between A and B, otherwise the output signal will sufferdistortion.

Various configurations of single transistor amplifier are possible, with some providingcurrent gain, some voltage gain, and some both.

From mobile phones to televisions, vast numbers of products include amplifiers forsoundreproduction,radio transmission, and signal processing. The first discrete transistor audioamplifiers barely supplied a few hundred milliwatts, but power and audio fidelity

gradually increased as better transistors became available and amplifier architectureevolved.

Modern transistor audio amplifiers of up to a few hundred watts are common andrelatively inexpensive.

Some musical instrument amplifier manufacturers mix transistors and vacuum tubes inthe same circuit, as some believe tubes have a distinctive sound.
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8. RADIO FREQUANCY TRANSMITTER:RECEIVER

RF modem can be used for the application that need two way wireless data

transmission. It features high data rates (9600 bps fixed) and longer transmission

distance (100mts). The communication protocol is self controlled and completely

transparent to user interface. The module can be embedded to your current design

so that wireless communication can be set easily.

Operation :

Module works in the half-duplex mode. Means it can both transmit and receivebut not both at the same time. Module has packet buffer of 128 bytes. When

receiving 128 bytes from serial port, it will send data out at once. If the data

package received is below 128 bytes, the module will wait for about 30ms and

then send it. In order to send data immediately, 128 bytes data per transmission is

necessary. After each transmission, module will be switched to receiver mode

automatically. The switch time is about 5ms. The LED for TX and RX indicates

whether module is currently receiving or transmitting data. The data send is

checked for CRC error if any, the transmitter sends out data up to 15 times till

data is correctly received.

9. DB9 Connector


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In the photograph below, the connector on the left is a 9-pin (DE-9) connector plug. The

hexagonal pillars at either end of each connector have a threaded stud (not visible) thatpasses through flanges on the connector, fastening it to the metal panel. They also have athreaded hole that receives thejackscrews on the cable shell, to hold the plug and sockettogether.

Possibly because the original PC used DB25 connectors for the serial andparallel ports,many people,[who?] not knowing the significance of the letter "B" as the shell size, began tocall all D-sub connectors "DB" connectors instead of specifying "DA," "DC" or "DE."When the PC serial port began to use 9-pin connectors, they were often called "DB9"instead of DE9. It is now common to see DE9 connectors sold as "DB9" connectors.DB-9 is nearly always intended to be a 9 pin connector with anEsize shell.

10. Rectifiers

It is used to convert alternating current into direct current. Alternating current being bi-

directional flows in one direction during positive half cycle and in other direction during

negative half cycle. There can be half wave rectifier circuit or a full wave bridge rectifier

circuit. There are several ways of connecting diodes to make a rectifier to convert AC to

DC. The bridge rectifier is the most important and it produces full-wave varying DC. A

full-wave rectifier can also be made from just two diodes if a centre-tap transformer is

used, but this method is rarely used now that diodes are cheaper. A single diode can be

used as a rectifier but it only uses the positive (+) parts of the AC wave to produce half-wave varying DC.
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Fig:Basic Half Wave Rectifier Circuit

Fig :Full Wave Rectifier using a Center-tapped Transformer.

Fig : full wave Rectified Output is filtered by C1

Fig :This Circuit Performs Identically tothat Shown in Figure 3

In mains-supplied electronic systems the AC input voltage must be converted into a DC

voltage with the right value and degree of stabilization. Figures 1 and 2 show the simplest

rectifier circuits. In these basic configurations the peak voltage across the load is equal to

the peak value of the AC voltage supplied by the transformers secondary winding. Formost applications the output ripple produced by these circuits is too high. However, for

some applications - driving small motors or lamps, for example - they are satisfactory. If

a filter capacitor is added after the rectifier diodes the output voltage waveform is

improved considerably. Figures 3 and 4 show two classic circuits commonly used to

obtain continuous voltages starting from an alternating voltage. The Figure 3 circuit uses

a center-tapped transformer with two rectifier diodes while the Figure 4 circuit uses a

simple transformer and four rectifier diodes.

11. Diodes:


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In electronics, a diode is a two-terminal device (except that thermionic diodes may also

have one or two ancillary terminals for a heater). Diodes have two active electrodes

between which the signal of interest may flow, and most are used for their unidirectional

current property. The varicap diode is used as an electrically adjustable capacitor.

Currentvoltage characteristic

A semiconductor diode's currentvoltage characteristic, or IV curve, is related to the

transport of carriers through the so-called depletion layerordepletion region that exists at

thep-n junction between differing semiconductors. When a p-n junction is first created,

conduction band (mobile) electrons from the N-doped region diffuse into the P-doped

region where there is a large population of holes (places for electrons in which no

electron is present) with which the electrons "recombine". When a mobile electron

recombines with a hole, both hole and electron vanish, leaving behind an immobile

positively charged donor on the N-side and negatively charged acceptor on the P-side.

The region around the p-n junction becomes depleted ofcharge carriers and thus behaves

as an insulator.

However, the depletion width cannot grow without limit. For each electron-hole pair that

recombines, a positively-charged dopant ion is left behind in the N-doped region, and a

negatively charged dopant ion is left behind in the P-doped region. As recombination

proceeds and more ions are created, an increasing electric field develops through the

depletion zone which acts to slow and then finally stop recombination. At this point, there

is a "built-in" potential across the depletion zone.

If an external voltage is placed across the diode with the same polarity as the built-in

potential, the depletion zone continues to act as an insulator, preventing any significant

electric current flow. This is the reverse biasphenomenon. However, if the polarity of the
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external voltage opposes the built-in potential, recombination can once again proceed,

resulting in substantial electric current through the p-n junction. For silicon diodes, the

built-in potential is approximately 0.6 V. Thus, if an external current is passed through

the diode, about 0.6 V will be developed across the diode such that the P-doped region is

positive with respect to the N-doped region and the diode is said to be "turned on" as it

has a forward bias.

A diodes IV characteristic can be approximated by four regions of operation .

IV characteristics of a P-N junction diode (not to scale).

Fig: 2.8

12. Capacitors:

A capacitor is an electrical/electronic device that can store energy in the electric field

between a pair ofconductors (called "plates"). The process of storing energy in the

capacitor is known as "charging", and involves electric charges of equal magnitude, but

opposite polarity, building up on each plate

Electric circuits

Fig: 2.9
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The electrons within dielectric molecules are influenced by the electric field, causing the

molecules to rotate slightly from their equilibrium positions. The air gap is shown for

clarity; in a real capacitor, the dielectric is in direct contact with the plates. Capacitors

also allow AC current to flow and block DC current.

DC sources

The dielectric between the plates is an insulator and blocks the flow of electrons. A

steady current through a capacitor deposits electrons on one plate and removes the same

quantity of electrons from the other plate. This process is commonly called 'charging' the

capacitor. The current through the capacitor results in the separation of electric charge

within the capacitor, which develops an electric field between the plates of the capacitor,

equivalently, developing a voltage difference between the plates.

This voltage V is directly proportional to the amount of charge separated Q. Since the

current I through the capacitor is the rate at which charge Q is forced through the

capacitor (dQ/dt), this can be expressed mathematically as:

where I is the current flowing in the conventional direction measured in amperes, dV/dt is

the time derivative of voltage measured in volts persecond, and C is the capacitance in

farads.For circuits with a constant (DC) voltage source and consisting of only resistors

and capacitors, the voltage across the capacitor cannot exceed the voltage of the source.

Thus, an equilibrium is reached where the voltage across the capacitor is constant and the

current through the capacitor is zero. For this reason, it is commonly said that capacitors

block DC.

AC sources

The current through a capacitor due to an AC source reverses direction periodically. Thatis, the alternating current alternately charges the plates: first in one direction and then the

other. With the exception of the instant that the current changes direction, the capacitor

current is non-zero at all times during a cycle. For this reason, it is commonly said that

capacitors "pass" AC. However, at no time do electrons actually cross between the plates,
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unless the dielectric breaks down. Such a situation would involve physical damage to the

capacitor and likely to the circuit involved as well.

Since the voltage across a capacitor is proportional to the integral of the current, as shown

above, with sine waves in AC or signal circuits this results in a phase difference of 90

degrees, the current leading the voltage phase angle. It can be shown that the AC voltage

across the capacitor is in quadrature with the alternating current through the capacitor.

That is, the voltage and current are 'out-of-phase' by a quarter cycle. The amplitude of the

voltage depends on the amplitude of the current divided by the product of the frequency

the current with the capacitance, C.

Types of capacitors used:

1. Electrolytic capacitors:

An electrolytic capacitor is a type ofcapacitortypically with a larger capacitance per

unit volume than other types, making them valuable in relatively high-current and low-

frequency electrical circuits. This is especially the case in power-supply filters, where

they store charge needed to moderate output voltage and current fluctuations, in rectifier

output, and especially in the absence of rechargeablebatteries that can provide similar

low-frequency current capacity. They are also widely used as coupling capacitors in

circuits where AC should be conducted but DC should not; the large value of the

capacitance allows them to pass very low frequencies.

Axial (top) and radial (bottom) electrolytic capacitors

2. Ceramic Capacitors:
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A Ceramic Capacitor is a capacitorconstructed of alternating layers ofmetal and

ceramic, with the ceramic material acting as the dielectric. Depending on the dielectric,

whetherClass 1 orClass 2, the degree of temperature/capacity dependence varies. A

ceramic capacitor often has (especially the class 2) high dissipation factor, high

frequency coefficient of dissipation.

Ceramic capacitors

13. Resistances:

A resistor is a two-terminal electrical orelectronic component that opposes an electriccurrent by producing a voltage drop between its terminals in accordance with Ohm's law:

The electrical resistance is equal to the voltage drop across the resistor divided by the

current through the resistor while the temperature remains the same. Resistors are used as

part ofelectrical networks and electronic circuits.

Four-band and five-band axial resistors

Four-band identification is the most commonly used color coding scheme on all resistors.

It consists of four colored bands that are painted around the body of the resistor. The

scheme is simple: The first two numbers are the first two significant digits of the

resistance value, the third is a multiplier, and the fourth is the tolerance of the value (e.g.

green-blue-yellow red : 56 x (10^4) ohms = 56 x 10000 ohms = 560 kohms 2%). Each

color corresponds to a certain number, shown in the chart below. The tolerance for a 4-

band resistor will be 1%, 5%, or 10%
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.

14. Crystal Oscillator:

A crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibratingcrystal ofpiezoelectric 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), toprovide a stable clock signal fordigital integrated circuits, and to stabilize frequencies forradio transmitters and receivers. The most common type of piezoelectric resonator used is thequartz crystal, so oscillator circuits designed around them were called "crystal oscillators".
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A miniature 4 MHz quartz crystal enclosed in a hermetically sealed HC-49/US package,used as the resonator in a crystal oscillator.

Operation:

A crystal is a solid in which the constituent atoms, molecules, orions are packed in aregularly ordered, repeating pattern extending in all three spatial dimensions.

Almost any object made of an elastic material could be used like a crystal, withappropriate transducers, since all objects have natural resonant frequencies of vibration.For example, steel is very elastic and has a high speed of sound. It was often used inmechanical filters before quartz. The resonant frequency depends on size, shape,

elasticity, and the speed of sound in the material. High-frequency crystals are typicallycut in the shape of a simple, rectangular plate. Low-frequency crystals, such as those usedin digital watches, are typically cut in the shape of a tuning fork. For applications notneeding very precise timing, a low-cost ceramic resonatoris often used in place of aquartz crystal.

When a crystal ofquartz is properly cut and mounted, it can be made to distort in anelectric field by applying a voltage to an electrode near or on the crystal. This property isknown aspiezoelectricity. When the field is removed, the quartz will generate an electricfield as it returns to its previous shape, and this can generate a voltage. The result is that aquartz crystal behaves like a circuit composed of an inductor, capacitorand resistor, with

a precise resonant frequency. (See RLC circuit.)

15. Transformer:

A transformer is a device that transfers electrical energy from onecircuit to another through

inductively coupledelectrical conductors. A changing currentin the first circuit (theprimary) creates

changing magnetic field; in turn, this magnetic field induces a changing voltage in the second circuit

(thesecondary). By adding a load to the secondary circuit, one can make current flow in the transform

thus transferring energy from one circuit to the other.

The secondary induced voltage VS, of an ideal transformer, is scaled from the primary VP

by a factor equal to the ratio of the number of turns of wire in their respective windings:
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15.1 Basic principles

The transformer is based on two principles: firstly that an electric current can produce a

magnetic field (electromagnetism) and secondly that a changing magnetic field within a

coil of wire induces a voltage across the ends of the coil ( electromagnetic induction). Bychanging the current in the primary coil, it changes the strength of its magnetic field;

since the changing magnetic field extends into the secondary coil, a voltage is induced

across the secondary.

An ideal step-down transformer showing magnetic flux in the core

Fig: 2.14

A simplified transformer design is shown to the left. A current passing through theprimary coil creates a magnetic field. The primary and secondary coils are wrapped

around a core of very high magnetic permeability, such as iron; this ensures that most of

the magnetic field lines produced by the primary current are within the iron and pass

through the secondary coil as well as the primary coil.

15.2 Induction law

The voltage induced across the secondary coil may be calculated from Faraday's law of

induction, which states that:

where VS is the instantaneous voltage, NS is the number of turns in the secondary coil and

equals the magnetic flux through one turn of the coil. If the turns of the coil are

oriented perpendicular to the magnetic field lines, the flux is the product of the magnetic

field strength B and the area A through which it cuts. The area is constant, being equal to

the cross-sectional area of the transformer core, whereas the magnetic field varies with

time according to the excitation of the primary. Since the same magnetic flux passesthrough both the primary and secondary coils in an ideal transformer, [1] the instantaneous

voltage across the primary winding equals

Taking the ratio of the two equations for VS and VP gives the basic equation[5] for

stepping up or stepping down the voltage
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Losses :

1. Winding resistance

Current flowing through the windings causes resistive heating of the conductors.At higher frequencies, skin effect and proximity effect create additional windingresistance and losses.

2. Hysteresis losses

Each time the magnetic field is reversed, a small amount of energy is lost due to

hysteresis within the core. For a given core material, the loss is proportional to thefrequency, and is a function of the peak flux density to which it is subjected.[25]

3. Eddy currents

Ferromagnetic materials are also good conductors, and a solid core made fromsuch a material also constitutes a single short-circuited turn throughout its entirelength. Eddy currents therefore circulate within the core in a plane normal to theflux, and are responsible forresistive heating of the core material. The eddycurrent loss is a complex function of the square of supply frequency and inversesquare of the material thickness.[25]

4. Magnetostriction

Magnetic flux in a ferromagnetic material, such as the core, causes it to physicallyexpand and contract slightly with each cycle of the magnetic field, an effectknown as magnetostriction. This produces the buzzing sound commonlyassociated with transformers,[13] and in turn causes losses due to frictional heatingin susceptible cores.

5. Mechanical losses

In addition to magnetostriction, the alternating magnetic field causes fluctuatingelectromagnetic forces between the primary and secondary windings. These incitevibrations within nearby metalwork, adding to thebuzzing noise, and consuminga small amount of power.[26]
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6. Stray losses

Leakage inductance is by itself lossless, since energy supplied to its magnetic

fields is returned to the supply with the next half-cycle. However, any leakageflux that intercepts nearby conductive materials such as the transformer's supportstructure will give rise to eddy currents and be converted to heat.[27]

16. Webcam :

Webcams are video capturing devices connected to computers orcomputer networks,

often using USB or, if they connect to networks, ethernet orWi-Fi. They are well known

for their low manufacturing costs and flexible applications.

Videoconferencing

As webcam capabilities have been added to instant messaging text chat services such asAOL Instant Messenger, one-to-one live video communication over the internet has nowreached millions of mainstream PC users worldwide. Increased video quality has helped

webcams encroach on traditional video conferencing systems. New features such aslighting, real-time enhancements (retouching, wrinkle smoothing and vertical stretch) canmake users more comfortable, further increasing popularity. Features and performancevary between programs.

Videoconferencing support is included in programs as Yahoo Messenger, AOL InstantMessenger(AIM), Windows Live Messenger,Skype,iChat,Paltalk(now PaltalkScene),Ekiga , Stickam,Tokbox, Camfrog and meetcam.
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Some online video broadcasting sites have taken advantage of this technology to createinternet television programs centered around two (or more) people "diavlogging" witheach other from two different places. Among others, BloggingHeads.tv uses thistechnology to set up conversations between prominent journalists, scientists, bloggers,and philosophers.

As a control input device

Special software can use the video stream from a webcam to assist or enhance a user'scontrol of applications and games. Video features, including faces, shapes, models andcolors can be observed and tracked to produce a corresponding form of control. Forexample, the position of a single light source can be tracked and used to emulate a mousepointer, a head mounted light would allow hands-free computing and would greatly

improve computer accessibility. This can also be applied to games, providing additionalcontrol, improved interactivity and immersiveness.

FreeTrackis a free webcam motion tracking application forMicrosoft Windows that cantrack a special head mounted model in up to six degrees of freedom and output data tomouse, keyboar

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