Test Rig Security & Monitoring System

8/10/2019 Test Rig Security & Monitoring System

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TEST RIG SECURITY & MONITORING SYSTEM

DEPT OF E&C, APSCE Page 1

CHAPTER 1

INTRODUCTION

PC BASED SAFETY AND SECURITY MONITORING ANALYSIS AND

WARNING SYSTEM FOR FIGHTER AIRCRAFT SIMULATION TEST RIGis detection and

warning of human influence in the test rig equipment it also gives detection and warning of the

pressure and temperature of the pumps. The project gives the platform for analyzing of the

parameters like pressure and temperature in the pumps of hydraulic section.

The test rig area is separated by three sections viz, test rig equipment, hydraulic section and

control room. Test rig equipment has the architecture similar to the aircraft where each and every

individual part is tested. A hydraulic section performs the work of sending temperature and pressure

to the aircrafts for those which are being tested according to the aircraft design it behaves like the

heart of the system. Hydraulic section comprises of two main pumps and two sub pumps with each

pair set for temperature and pressure separately. Finally control room is the place where all the

simulation process is done.

So if there is a human intervention in the rig area, indication is given to the control room

through pc display and the alert to human as well as in control room using buzzer.

The rig area consists of 4 pumps, 2 main pumps and 2 sub pumps which are located in the

hydraulic section. These pumps provide constant pressure and temperature to the test rig area for

testing aircrafts.

If the pressure and the temperature value crosses the critical values it will damage the test

rig equipment and as well as aircraft also. We can also update the pressure and the temperature

values when required.


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So in case of any variations in the temperature and the pressure indication is given by pc

display and alert is given by buzzer in the control room.


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CHAPTER 3

BLOCK DIAGRAM


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BLOCK DIAGRAM EXPLANATION

IR TRANSMITTER AND RECEIVER MODULE:-

IR Transmitter and receiver module is a major part of this system. It plays a very important

role in detection of the human interference in the rig area. The IR transmitter will be continuously

transmitting the high signal and the receiver will be receiving the signals. When a person enters in

between this area the receiver will not receive any signal and a low signal is sent to the next stage

which is a buffer stage.

BUFFER DRIVER:-

The buffer is used to match the impedance and the driver consists of the amplifier stage

with the Darlington pair configuration.

RELAY:-

The relay we use here is the electromechanical relay which is used to connect to the

parallel port. The relay drives the parallel port.

RF

RECIEVER

MICROCONTROLLER

AT89C51

LCD

DISPLAY


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TEMPERATURE SENSOR:-

The temperature sensor we use here is DR-25. This sensor acts as a negative temperature co-

efficient, as the temperature increases the resistance decreases. The output of this sensor is fed to the

comparator stage.

COMPARATOR:-

This stage is used for comparison purpose. In this stage we set one reference value and then

compare other to inputs with this value. Then the output of the comparator is given to the

optocoupler stage. When there is a variation in the temp/illumination in the thermistor, it measures

impedance of the sensor smartly and decides which gate to open. The circuit diagram shows that

three operational amplifiers compare the drop across the test leads to a fixed voltage and indicate

which of the two is highest by switching their output to the positive supply level or ground.

OPTO-COUPLER:-

The Opto-coupler IC has a photo diode which illuminates whenever input signal

appears. Then it couples the signal to the driver stage. Then in the driver stage the impedance is

matched and sent to the relay and further to the computer for displaying purpose.

POTENTIOMETER:-The potentiometer is the physical device where we have a provision to vary the

resistance. First we set one threshold value for this upon varying the potentiometer below and above

the threshold value the pressure can be detected. Then the varying signal is given to the comparator

section to compare and then it is given to the opto-coupler stage and then to relay and finally to

driver and relay.

PARALLEL PORT AND MONITOR:-

The low signals from the relay are given to the parallel port. The parallel port is used to

connect between our hardware circuit and the computer. In monitor using any of the software we

display the temperature values, pressure values and can view the persons entering in the zone. The

monitor is kept in the control room for the display purpose.


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CHAPTER 3

HARDWARE DESCRIPTION

3.1 POWER SUPPLY UNIT

CIRCUIT DIAGRAM OF +5V & +12V FULL WAVE REGULATED POWER

The circuit needs two different voltages, +5V & +12V, to work. These dual voltages are

supplied by this specially designed power supply. The power supply, unsung hero of every electronic

circuit, plays very important role in smooth running of the connected circuit. The main object of this

power supply is, as the name itself implies, to deliver the required amount of stabilized and pure

power to the circuit. Every typical power supply contains the following sections:

1.Step-down Transformer:The conventional supply, which is generally available to the user, is 230V

AC. It is necessary to step down the mains supply to the desired level. This is achieved by using

suitably rated step-down transformer. While designing the power supply, it is necessary to go for

230A C

D

C

C

IC17812

D

C

IC1780

+12V

+5V


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little higher rating transformer than the required one. The reason for this is, for proper working of the

regulator IC (say KIA 7805) it needs at least 2.5V more than the expected output voltage

2. Rectifier stage:Then the step-downed Alternating Current is converted into Direct Current. This

rectification is achieved by using passive components such as diodes. If the power supply is

designed for low voltage/current drawing loads/circuits (say +5V), it is sufficient to employ full-

wave rectifier with centre-tap transformer as a power source. While choosing the diodes the PIV

rating is taken into consideration.

3. Filter stage:But this rectified output contains some percentage of superimposed a.c. ripples. So

to filter these a.c. components filter stage is built around the rectifier stage. The cheap, reliable,

simple and effective filtering for low current drawing loads (say upto 50 mA) is done by using shunt

capacitors. This electrolytic capacitor has polarities, take care while connecting the circuit.

4. Voltage Regulation: The filtered d.c. output is not stable. It varies in accordance with the

fluctuations in mains supply or varying load current. This variation of load current is observed due to

voltage drop in transformer windings, rectifier and filter circuit. These variations in d.c. output

voltage may cause inaccurate or erratic operation or even malfunctioning of many electronic circuits.

For example, the circuit boards which are implanted by CMOS or TTL ICs.

1 2 3

KIA


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The stabilization of d.c. output is achieved by using the three terminal voltage regulator IC.

This regulator IC comes in two flavors: 78xx for positive voltage output and 79xx for negative

voltage output. For example 7805 gives +5V output and 7905 gives -5V stabilized output. These

regulator ICs have in-built short-circuit protection and auto-thermal cutout provisions. If the load

current is very high the IC needs heat sink to dissipate the internally generated power.

Circuit Description:

A d.c. power supply which maintains the output voltage constant irrespective of a.c. mains

fluctuations or load variations is known as regulated d.c. power supply. It is also referred as full-

wave regulated power supply as it uses four diodes in bridge fashion with the transformer. This

laboratory power supply offers excellent line and load regulation and output voltages of +5V & +12

V at output currents up to one amp.

1. Step-down Transformer: The transformer rating is 230V AC at Primary and 12-0-12V,

1Ampers across secondary winding. This transformer has a capability to deliver a current of

1Ampere, which is more than enough to drive any electronic circuit or varying load. The 12VAC

appearing across the secondary is the RMS value of the waveform and the peak value would be 12 x

1.414 = 16.8 volts. This value limits our choice of rectifier diode as 1N4007, which is having PIV

rating more than 16Volts.

2. Rectifier Stage:The two diodes D1 & D2 are connected across the secondary winding of the

transformer as a full-wave rectifier. During the positive half-cycle of secondary voltage, the end A of

the secondary winding becomes positive and end B negative. This makes the diode D1 forward

biased and diode D2 reverse biased. Therefore diode D1 conducts while diode D2 does not. During

the negative half-cycle, end A of the secondary winding becomes negative and end B positive.

Therefore diode D2 conducts while diode D1 does not. Note that current across the centre tap

terminal is in the same direction for both half-cycles of input a.c. voltage. Therefore, pulsating d.c. is

obtained at point C with respect to Ground.

3. Filter Stage:Here Capacitor C1 is used for filtering purpose and connected across the rectifier

output. It filters the a.c. components present in the rectified d.c. and gives steady d.c. voltage. As the

rectifier voltage increases, it charges the capacitor and also supplies current to the load. When

capacitor is charged to the peak value of the rectifier voltage, rectifier voltage starts to decrease. As


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the next voltage peak immediately recharges the capacitor, the discharge period is of very small

duration. Due to this continuous charge-discharge-recharge cycle very little ripple is observed in the

filtered output. Moreover, output voltage is higher as it remains substantially near the peak value of

rectifier output voltage. This phenomenon is also explained in other form as: the shunt capacitor

offers a low reactance path to the a.c. components of current and open circuit to d.c. component.

During positive half cycle the capacitor stores energy in the form of electrostatic field. During

negative half cycle, the filter capacitor releases stored energy to the load.

4. Voltage Regulation Stage:Across the point D and Ground there is rectified and filtered d.c. In

the present circuit KIA 7812 three terminal voltage regulator IC is used to get +12V and KIA 7805

voltage regulator IC is used to get +5V regulated d.c. output. In the three terminals, pin 1 is input

i.e., rectified & filtered d.c. is connected to this pin. Pin 2 is common pin and is grounded. The pin 3

gives the stabilized d.c. output to the load. The circuit shows two more decoupling capacitors C2 &

C3, which provides ground path to the high frequency noise signals. Across the point E and F

with respect to ground +5V & +12V stabilized or regulated d.c output is measured, which can be

connected to the required circuit.

Note: While connecting the diodes and electrolytic capacitors the polarities must be taken into

consideration. The transformers primary winding deals with 230V mains, care should be taken with

it.

3.2 IR TRANS-RECEIVER MODULE

These IR Transmitter and two IR Receivers are fitted on front side of vehicle and are continuously

switched ON for obstacle detection purpose.

3.2.1 IR TRANSMITTERThe circuit components are explained as:

IR LED:The IR LED or Infra Red Light Emitting Diode is an electronic device which gives off or

emits light when current is passed through it. Like general diode, this IR LED passes current only in

one direction and requires forward operation voltage of about 2V and forward operation current in

10 to 20 mA range. Maximum reverse voltage that the IR LED can withstand is typically 3 to 5V,


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more than this could damage the component. It does not have any current control function, so, when

the IR LED is used in a circuit, a resistor must be used in series to limit the current flow through it. If

greater range is required, this resistor may be reduced to a minimum value with a consequent

adverse effect on current consumption. Do not reduce the value of resistor unless you do require the

greater range, otherwise the relay may not trip reliably close in due to reflections caused by the high

light output. For a good range, the current through the LEDs must be large. Since, however, currents,

the pulses must be short, and this is why PDM is used (In this type of modulation, the time of

occurrence of the first and last transition edge, is varied from its unmodulated position).

When the IR LED is used in an application such as the remote controlling transmitter, where the

battery is the main source of current, providing continuous high current to keep the IR LED ON will

consume too much of power. So when the power is applied to the IR LED, the supply is provided as

pulses. If the pulse repetition frequency is rapid enough (more than 50 Hz) then to the receiver eye

the IR LED will appear as continuously ON. For example, instead of supplying 25 mA current

continuously, one can provided 50 mA current as pulse to get brighter light output with the same

power consumption.

The Infrared diode used is of plastic pack and is similar in appearance to the familiar Red

LED, except that the plastic encapsulation is deep violet colour.

As stated earlier, the IR Remote Controlling system consists of a set of an IR transmitter and an IR

receiver. Whenever the IR transmitter is activated, it generates a invisible Infra-red light beam signal

and transmits an it towards the IR receiver. The transmitters and receivers are positioned facing each

other.

The source of light in the transmitter is an Infrared LED and rather than merely providing a

continuous source of light, it is flashed on and off at about 10Khz.This is done so that the receiver

can selectively amplify the signal from the transmitter and completely reject ambient light.

The information is passed from the IR Transmitter and Receiver in the form of combinational

digital pulse signals. These pulses are transmitted to the receiver by modulating a carrier frequency

using Pulse Code Modulation [PCM] method. That means it uses pulse-duration (pulse-width)

modulation. The modulated signal is produced in the traditional manner of having the audio signal

set against a pure high-frequency triangular signal generator can be found on 55. If another generator


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is used, make sure that its off-set is equal to half the supply voltage of 5 V and its peak value is 2.5

Vpp.

3.2.2 PCM IR TRANSMITTER IC

PCM IR Transmitter IC:

This 20 pin DIL packaged IC has integrated all the necessary stages to transmit the IR pulse

beams to the receiver. As the pin-out diagram of the IC shows, pin-20 is supply pin and pin-18 is

ground pin. Since the IC has in-built Oscillator circuit, whose frequency can be adjusted between

445 K Hz and 510 K Hz, it needs outer components to oscillate with transmitter circuit needs. SO to

get the calculated frequency range, specific value crystal and capacitors are connected to the pin-2

[OSC IN] and output is taken on pin-3 [OSC OUT]. This frequency is used by the IC as a reference

frequency to oscillate. The pin-19 is the out pin, which is fed to the transmitter circuit.

The IC can be used in two modes: Flash Mode, where pin-1 [Transmission Mode pin] is

connected with Supply pin and the average current consumption is 6.5 mA; Carrier Mode, where

pin-1 is connected to ground and average current consumption is around 13 mA.


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CIRCUIT DIAGRAM OF IR TRANSMITTER

Circuit Description

The Infra Red Transmitter is made very simple by employing the dedicated & commercially

available IC1. Here the IC1 is used in flash mode by connecting Transmission Mode Pin 1 to +Vcc,

and thus reduces average current consumption to 6.5 mA. In this mode minimum and maximum

transmission times are 2.1 milliseconds and 3.6 milliseconds respectively and the duty cycle is 0.7%.

Since the Circuit is intended to send only one signal code, IC1 is configured for address one

[refer the table in IC description] by making all the Address Input pins, Code pins to zero or ground.

As soon the switch S1 is switched ON, the circuit gets its working voltage of 9 Volts through pin-20.

Inside the IC, it creates the address 1 as a command code and sent to the output pin-19.

S1

C3

C2

Infra-Red

LEDs

R2

R1

2

3

Signal

Diodes

C1

+Vcc

X1

IC1

20 1

18

15

19


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This command signal output from the IC1 is given through a resistor R1 to the base of the

Transistor T1. The output from this transistor T1 is fed to the base of another Transistor T2. These

two transistors amplify the command signal to the sufficient level and then drive the IR LEDs. The

Collector of both the transistors is connected to the pair of Infra Red LEDs. When the transistor T2

goes to saturation region, that means starts conducting, the current will flow through the two series

IR LEDs. Thus they illuminate for that period and gets off. This process continues as per the switch

S1 is pushed ON and the pulses will be sent through IR LEDs continues. Thus the command signal

is transmitted to IR receiver successfully.

3.2.3 IR Receiver

The packets of infra-red light transmitted from the IR Transmitter of the user remote

control are received on a sensor module which is sensitive to infra-red light. Next, the signal is

converted back into electrical pulses by a 36 KHz receiver and an associated detector. And that

electrical pulse is fed to driver circuit, which in result supply trigger pulse to Schmitt Trigger circuit.

The circuit components are explained as:

IR Receiver eye

An IR Receiver Eye is a module, which is encapsulated with Photo Transistor whose semiconductor

junction is mounted beneath an optical lens. It is normally used in its open base configuration and act

as a light-to-voltage converter. The base is open; the value of the reverse current across collector and

emitter will depend on the amount of illumination on the base face. In dark conditions it is near zero

and under bright light it is tens or hundreds of mA.


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Circuit Description

This circuit activates the relay whenever there is a presence of Infra Red Rays. The working

principle of this module is very simple:

Power Supply

The mains voltage is step-down to 6V using a transformer. This secondary 6V is rectified

using full-wave rectifier, which is composed by D1 & D2 diodes. This is further filtered using

electrolytic capacitor C2 and fed to regulator IC1. This three-terminal IC stabilizes the input and

gives out the constant +5V as working voltage for the circuit.

D

R

R

C

D

C

C

R

R

R

R

T

InfraRed

IC2

IC1

D O

I

G

23

0

N/

C

To Trains

Power Supply IR Receiver Driver


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IR Receiver

The IR Sensor Module has 3 terminals: signal input, supply pin and the ground pin. This

module works on regulated +5Votls, and exceeding this limit may cause the damage of it. So, this

Sensor is given Vcc through a biasing resistor R1 and grounded pin is given to negative terminal of

the supply. Whenever the Infra Red rays falls on this Sensors eye [that black mole on Sensor] it

produces varying signal voltages at output pin. This is given to amplifier stage built by an PNP

transistor TR1 through an current limiting resistor R2. The output of this amplifier is fed to a buffer

situated in IC2. This buffer or converter enhances the current capacity of the signal and send to

driver stage. The signal output is monitored by observing the glowing indicator LED D4.

Driver & Circuit Breaker:

The driver is built around TR1 and a low-impedance relay. The signal diode D3 is there toprevent the back e.m.f produced by the switching action of the relay. When user does not press any

key, the receiver does not receive any IR rays from the opposite end, and hence No signals to TR2

base.

As this E-Power Supply units Receiver senses interrupt of IR Rays from the opposite IR

Transmitter, it alerts driver section. The IR signal from the buffer enters the base of TR2, it

undergoes saturation and activates the relay RL1. Since, relay RL1s N/O [Normally Open] pins are

connected to Schmitt Trigger Circuit.

Note: The circuit is fully stabilized from the false triggering and other interferences. This is

achieved by using capacitors at proper places. As this is an Unlatch Circuit the relay actuates only

when the IR beams are present at the eye of the sensor module. And releases the switching as-

soon-as there are no IR radiations.


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3.3 DR-25 TEMPERATURE SENSOR

DR-25 heat-shrinkable tubing is flexible and abrasion resistant. It is made from a radiation

cross-linked elastomeric material specially formulated for optimum high temperature fluid

resistance, and long term heat resistance. The operating temperature of DR-25 tubing is from -75Cto +150C for long periods. Shrinking to 50% of its supplied diameter when heated, 10 standard

sizes of DR-25 tubing will cover the diameter range from 1.6 mm to 70 mm.

DR-25 tubing is suitable as a jacketing material for military vehicle cables and harnesses.

When used in conjunction with System-25 heat-shrinkable moulded shapes and S1125 high

performance adhesive, these products provide a complete cable harness system capability.

DR-25 temperature sensor acts as a negative temperature co-efficient, as the temperature

increases the resistance reduces. The equivalent temperature is taken into the comparator section and

compared with the threshold value. The DR-25 flexible fluid resistant elastomeric tubing,

developed from DR-25, is a thin wall version ideal for use where space and weight saving are

important. It also offers excellent resistance to fluids at high temperature and to long-term heat

exposure. It has a shrink ratio of 2:1 and can withstand high temperature.

The figure above shows the neat picture of DR-25 temperature sensor. This has a minimum

full recovery temperature of +175C. Its weight is 7 gram per meter. It has a spool quantity of 50

meter. After heating it recovers up to 1.6m in diameter.


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3.4 Potentiometer

A potentiometer is a three-terminal resistor with a sliding contact that forms an adjustable

voltage divider. If only two terminals are used (one side and the wiper), it acts as a variable resistor

or rheostat. Potentiometers are commonly used to control electrical devices such as volume controlson audio equipment. Potentiometers operated by a mechanism can be used as position transducers,

for example, in a joystick.

Potentiometers are rarely used to directly control significant power, since the power

dissipated in the potentiometer would be comparable to the power in the controlled load. Instead

they are used to adjust the level of analog signals (e.g. volume controls on audio equipment), and as

control inputs for electronic circuits. For example, a light dimmer uses a potentiometer to control the

switching of a TRIAC and so indirectly control the brightness of lamps.

Fig. Potentiometer

3.4.1 Theory of operation

The potentiometer can be used as a voltage divider to obtain a manually adjustable output

voltage at the slider (wiper) from a fixed input voltage applied across the two ends of the

potentiometer. This is the most common use of them.


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The

voltage across RL can be calculated by:

If RL is large compared to the other resistances (like the input to an operational amplifier),

the output voltage can be approximated by the simpler equation:

Potentiometer applications

Potentiometers are widely used as user controls, and may control a very wide variety of

equipment functions. The widespread use of potentiometers in consumer electronics has declined in

the 1990s, with digital controls now more common. However they remain in many applications,

such as volume controls and as position sensors

One of the most common uses for modern low-power potentiometers is as audio control

devices. Both linear potentiometers and rotary potentiometers are regularly used to adjust loudness,

frequency attenuation and other characteristics of audio signals.

The 'log pot' is used as the volume control in audio amplifiers, where it is also called an

"audio taper pot", because the amplitude response of the human ear is also logarithmic. It ensures

that, on a volume control marked 0 to 10, for example, a setting of 5 sounds half as loud as a settingof 10. There is also an anti-log pot or reverse audio taper which is simply the reverse of a

logarithmic potentiometer. It is almost always used in a ganged configuration with a logarithmic

potentiometer, for instance, in an audio balance control. Potentiometers used in combination with

filter networks act as tone controls or equalizers.


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3.5 CIRCUIT DIAGRAM OF TEMPERATURE AND PRESSURE

D

D

R

R

R

D

T5

T

1

D

A

A

1

1

5

2

1

1

1

3

R

R

R

D

D

4

76

P

P

R

R

R

R

R

R

R

R

A

A

A

T3

R

R

TEMP

/LDRSENS

RL

R

A1 TO A3

R

I

I

I

COMPARATO

OPTOCOU

DRIVER

RL

B

RL


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Operational Amplifier

Designed originally for analogue computer and control applications, the operational amplifier

has found its way into almost every field of electronics. Todays Integrated Circuit Op-Amps offer

many advantages over their discrete component predecessors. Circuit design is greatly simplified

with the added bonus that the characteristics of the latest generation of Op-Amps, far exceed those of

their predecessors.

An Op-amp is a direct coupled high gain amplifier, usually consisting of one or more

differential amplifiers and usually followed by a level translator and an output stage. Output stage is

generally a push-pull or push-pull complementary symmetry pair. An Op-amp is available as single

IC package. The maximum common mode voltage that can be applied to an Op-amp without

disturbing its proper function is of the order +13 V or13 V.

THE DESIRABLE CHARACTERISTICS OF OP-AMPS ARE:

a) The open-loop voltage gain should be very high (ideally infinity).

b) The input resistance should be very high (ideally infinity).

c) The output resistance should be very low (ideally zero).

d) Full power bandwidth should be as wide as possible.

e) Slew rate should be as large as possible.

f) Input offset should be as small as possible.g) CMRR should be as large as possible.

ELECTRICAL PARAMETERS OF OP-AMP:

1. I/p off-set voltage (Vio):

It is the voltage that must be applied between the two input terminals of an op-amp to verify

the output to be null.

2. I/p off-set current (Iio):

The algebraic difference between the current into the inverting and noninverting terminal

is reffered as input Off-set current.


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3.I/p Bias current:

It is the average of the current that flow into inverting and non-inverting input terminalsof the

Op-amp.In the equation form:

IB= (IB1+IB2) / 2

4. Differential I/p resistance:

It is the equivalent resistance that can be measured at either terminal connected to group.

5. I/p capacitance:

It is the equivalent capacitance that can be measured at either the inverting or non-inverting

input terminal with the either terminal connected to ground .

6.CMRR (Common Mode Rejection Ratio ):

The CMRR is defined as the ratio of differential voltage gain Ad to thecommon voltage

gain Acm

CMRR = Ad / Acm .

The higher the value of CMRR ,better is the matching between two input terminals and

smaller is the output common mode voltage .

7. SVRR (Supply Voltage Rejection Ratio ):

The change in OP-amps input OFF SET voltage Vio caused by variation in supply voltages

is called the SVRR . These are expressed in v / v or in dBs

SVRR = Vio / V .

Where ,Vio = input offset voltage & V= supply voltage

8. Input Voltage Range:

It is the maximum common mode voltage that can be applied to an Op-amp without

disturbing its proper function. It is of the order +13 V or13 V

9. Large Signal Voltage Gain:

Since the OP-amp amplifies difference voltage between two input terminals, the voltage gain

of the amplifier is defined as,

A= o/p Voltage / Diff. i/p Voltage = Vo / Vid.

10. Gain Bandwidth Product:

It is the bandwidth of the Op-amps when the gain is unity.


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11 Slew Rate:

It is defined as max. rate of change of output voltage / unit of time and is expressed in volts / sec.

| V / sec

SR = dvo / dt |

| max.

POWER DRIVING CIRCUITS:

In many applications, a relay will require some form of interface to the circuit to which it is

connected. Often such an interface need consist of nothing more than a single transistor. Almost any

n-p-n transistor with a current gain of 50 or more can be used in the circuit. However, it is important

to ensure that it is operated within its maximum collector current (IC(max)) rating. The coil resistance

of relay and preferred transistors are as follows: 50 ohm to 200 ohm - T1P31 (or equivalent), 200Ohm to 400 Ohm - BC142 (or equivalent), 400 Ohm to 1.2 K Ohm - BC108 (or equivalent). The

circuit requires an input current of about 0.5 mA when operated from a 5V source. In some

applications it may be desirable to increase the sensitivity of the circuit, in which case a Darlington

driver stage can be used. A Darlington driver based on two (discrete) n-p-n devices requires a

current of only a mere 40A at 5V in order to operate the relay. This circuit can be used with relays

having coil resistance as low as about 200 ohm and will also operate reliable with an input current of

as little as 40A.

OPTO-COUPLER IC MCT 2E:

Buffers does not affect the logical state of a digital signal (i.e. logic 1 input results into logic

1 output where as logic 0 input results into logic 0 output). Buffers are normally used to provide

extra current drive at the output are used in interfacing applications. This 6-pin DIL packaged IC

MCT 2E acts as Buffer as-well-as Isolator. The input signals may be of 2.5 to 5V digital TTL

compatible or DC analogue the IC gives 5V constant signal output. The IC acts as isolator and

provides isolation to the main circuit from varying input signals. The working voltage of IC is fed at

pin-5 and input to pin-1. The pin-2 is ground and pin-4 is output. Note that pin-3 and pin-6 are not

available pins, which must be left free. And the isolated circuit must have its own ground

connection.


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The Opto-coupler IC has a photo diode which illuminates whenever input signal appears at

pin-1. A photo transistor, whose Base-lead open, receives the signal from the blinking photo diode

and passes it intact to the output pin-4. As this switching action is very fast, in term of micro

seconds, the signal transfer is successfully done without any delay and signal loss. As there is any

physical contact between photo diode and photo transistor is observed, it is used for isolating two

sections of the circuit. Especially the delicate digital circuits or signal sensitive stages whose output

is supposed to drive a fluctuating stage or mains operated load.

Since the digital outputs of the some circuits cannot sink much current, they are not capable

of driving relays directly. So, high-voltage high-current Darlington arrays are added to this opto-

coupler IC for interfacing low-level logic circuitry and peripheral power loads. Typical loads include

relays, solenoids, stepping motors, magnetic print hammers, multiplexed LED and incandescent

displays, and heaters.

Circuit Description:

COMPARATOR STAGE:

When there is a variation in the temp/illumination in the thermistor or ldr, it measures

impedance of the sensor smartly and decides which gate to open. The circuit diagram shows that

three operational amplifiers compare the drop across the test leads to a fixed voltage and indicate

which of the two is highest by switching their output to the positive supply level or ground [see the

accompanying table].

INPUT

GND

N/C

1

2

3

6

5

4

N/C

Vcc

OUTPUT

MCT2E OPTOCOUPLER


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3.6 RADIO FREQUENCY OPERATION

Radio must surely be one of the most fascinating aspects of electronics. This part of

explanation provides a brief introduction to radio communication before describing the circuitry of

RF receivers and transmitters. The aim has been to provide the user with sufficient information towhat his or her appetite for a subject which has a broad appeal to a large number of dedicated

enthusiasts all over the world

FM broadcasting

TV bands 1V/V

3 100 m

Very high frequency, VHF

SW broadcasting

MW broadcastingMedium frequency, MF

300 KHz 1 Km

LW broadcastingLow frequency, LF

10 Km30 KHz

Fig ( A) The Radio Frequency Spectrum

3 GHz 10 cm

Frequency Wavelength

30 MHz 10 m

30 MHz 1 m

Ultra high frequency, UHF

High frequency, HF


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3.6.1 Radio Frequency Signals:

Radio frequency signals are generally understood to occupy a frequency range, which

extends from a few tens of kilohertz to several hundred giga-hertz. The lowest part of radio

frequency range, which is of practical use (below 30 kHz), is only suitable for narrow-band

communications. At this frequency, signals propagate as ground waves (following the curvature of

the earth) over very long distance. At the other extreme, the highest frequency range, which is of

practical importance, extends above 30GHz. At these microwave frequencies, considerable

bandwidths are available (sufficient to transmit many television channel using point-to-point links or

to permit very high definition radar systems) and signals tend to propagate strictly along line -of-

sight paths.

At other frequencies, signals may propagate by various means, including reflection from

ionized layers in the ionosphere. At frequencies between 3MHz and 30MHz, for example,

ionospheric propagation regularly permits intercontinental broadcasting and communications using

simple equipment within the scope of the enthusiastic radio amateur and short-wave listener.

For convenience, the radio frequency spectrum is divided into a number of bands, each

spanning a decade of frequency. The use to which each frequency range is put depends upon a

number of factors, paramount amongst which is the propagation characteristic within the bandconcerned. Other factors, which need to be taken into account, include the efficiency of practical

aerial system in the range concerned and the bandwidth available. It is also worth noting that,

although it may appear from Figure A that a great deal of the radio frequency spectrum is not used, it

should be stressed that competition for frequency space is fierce. Frequency allocations are,

therefore, ratified by international agreement and the various user services carefully safeguard their

own areas of the spectrum.

Frequency and wavelength

Radio waves propagate in air (or space) at the speed of light (300 million meters per second).

The velocity of propagation[v], wavelength[] and frequency [f] of a radio wave are related by the

equation:


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V = f= 3 X 108

m/s

This equation can be arranged to make f or the subject, as follows:

F = 3 X 108/ Hz and = 3 X 10

8/ fm

As an example, a signal at a frequency of 1 MHz will have a wavelength of 300 m whereas a signal

at a frequency of 10 MHz will have a wavelength of 30m.

Modulation

In order to convey information using a radio frequency carrier, the signal information must

be superimposed or modulated onto the carrier. Modulation is the name given to the process of

changing a particular property of the carrier wave in sympathy with the instantaneous voltage (or

current) signal.

The most commonly used methods of modulation are amplitude modulation (AM) and

frequency modulation (FM). In the former case, the carrier amplitude (its peak voltage) varies

according to the voltage, at any instant, of the modulating signal. In the latter case, the carrier

frequency is varied in accordance with the voltage, at any instant, of the modulating signal.

Figure B shows the effect of amplitude and frequency modulating a sinusoidal carrier (notethat the modulating signal is, in the case, also sinusoidal). In practice, many more cycles of the radio

frequency carrier would occur in the time span of the cycle of the modulating signal.

The term angle modulation is the generic term encompassing both frequency modulation

and phase modulation. Frequency modulation involves operating directly upon the frequency

determining elements of an oscillator stage (e.g. by means of a variable capacitance diode placed

across the oscillator-tuned circuit or connected in series with a quartz crystal).

Phase modulation, on the other hand, acts indirectly by changing the phase of the signal in a

subsequent stage (e.g. by means of a variable capacitance diode acting in a phase shifting circuit).


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If the modulating signal (audio) is correctly tailored

prior to its application to the phase modulated stage,

the end result is identical to that of frequency

modulation. The reason for this is that, in a true FM

system, the deviation produced is the same for all

modulating signals of equal amplitude (i.e. the

amount frequency deviation is independent of the

frequency of the modulating signal). In a phase-

modulated system, on other hand, the amount of

frequency deviation is proportional to both

modulating signal amplitude and modulating signal

frequency. Thus in a phase modulated system without

audio tailoring, a modulation signal of 2 kHz will

produce twice as much frequency deviation as an

equal amplitude modulating signal of 1 kHz. The

desired audio response required to produce FM, therefore, is one, which rolls off the frequency

response by half for each doubling of frequency (equivalent to 6-dB per octave roll-off). This can be

easily achieved using a simple R-C low-pass filter.

Demodulation

Demodulation is the reverse of modulation and is the means by which the signal information

is recovered from the modulated carrier. Demodulation is achieved by means of a demodulator

consists of a reconstructed version of the original signal information present at the input of the

modulator stage within the transmitter.

Figure C shows the simplified block schematic of a simple radio communication system

comprising on AM transmitter and a tuned radio frequency (TRF) receiver. Within the transmitter,

the carrier wave (of constant frequency) is generated by means of a radio frequency oscillator stage.

In order to ensure that the carrier is both accurate and within in frequency, this stage would normally

employ a quartz crystal within its frequency generating circuitry.

Amplitude & Frequency Modulation


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The output of the modulator (a modulated carrier) is amplified before outputting to the aerial

system. The output is usually carefully filtered to remove any spurious signals (harmonics) which

may be present and which may otherwise cause interference to other services.

At the receiver, the signal produced by the receiving aerial is a weak copy of the transmitted

signal (its level is usually measured in a V). Also present will be countless other signals at different

frequencies (and some with appreciably larger amplitude than the desired signal). These unwanted

signals must be rejected by the receivers radio frequency tuned circuits if they are no to cause

problems in later stages.

3.6.2 RF TRANSMITTER MODULE

The RF transmitter is built around the ASIC and common passive and active components,

which are very easy to obtain from the material shelf. The circuit works on Very High Frequency

band with wide covering range. The Carrier frequency is 147 MHz and Data frequencies are 17

MHz, 19 MHz,22 MHz & 25 MHz. It should be noted that ASIC or Application Specific Integrated

Circuit is proprietary product and data sheet or pin details or working principles are not readily

available to the user.


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ASIC:

Application Specific Integrated Circuit [ASIC] is another option for embedded hardware

developers. The ASIC needs to be custom-built for a specific application, so it is costly. If the

embedded system being designed is a consumer item and is likely to be sold in large quantities, then

going the ASIC route is the best option, as it considerably reduces the cost of each unit. In addition,

size and power consumption will also be reduced. As the chip count (the number of chips on the

system) decreases, reliability increases.

If the embedded system is for the mass market, such as those used in CD players, toys, and

mobile devices, cost is a major consideration. Choosing the right processor, memory devices, and

peripherals to meet the functionality and performance requirements while keeping the cost

reasonable is of critical importance. In such cases, the designers will develop an Application Specific

Integrated Circuit or an Application Specific Microprocessor to reduce the hardware components

and hence the cost. Typically, a developer first creates a prototype by writing the software for a

general-purpose processor, and subsequently develops an ASIC to reduce the cost.

Oscillator:

An electronic device that generates sinusoidal oscillations of desired frequency is known as a

sinusoidal oscillator. Although we speak of an oscillator as generating a frequency, it should be

noted that it does not create energy, but merely acts as an energy converter. It receives d.c. energy

and changes it into a.c energy of desired frequency. The frequency of oscillations depends upon the

constants of the device.

A circuit which produces electrical oscillations of any desired frequency is known as an oscillatory

circuit or tank circuit. A simple oscillatory circuit consists of a capacitor (C) and inductance coil (L)

in parallel. This electrical system can produce electrical oscillations of frequency determined by the

values ofLand C. The sequence of charge and discharge results in alternating motion of electrons or

an oscillating current. The energy is alternately stored in the electric field of the capacitor and the

magnetic field of the inductance coil. This intercharge of energy between L and Cis repeated over

and again resulting in the production of oscillations.


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In order to obtain continuous undamped a.c. output from the tank circuit, it is necessary to supply the

correct amount of power to the circuit. The most practical way to do this is to supply d.c. power to

some device which should convert it to necessary a.c. power for supply to the tank circuit. This can

be achieved by employing a transistor circuit. Because of its ability to amplify, a transistor is very

efficient energy converter i.e. it converts d.c. power to a.c. power. If the damped oscillations in the

tank circuit are applied to the base of transistor, it will result in an amplified reproduction of

oscillations in the collector circuit. Because of this amplification more energy is available in the

collector circuit than in the base circuit. If a part of this collector-circuit energy is feedback by some

means to the base circuit in proper phase to aid the oscillations in the tank circuit, then its losses will

be overcome and continuous undamped oscillations will occur.

Hartley Oscillator is very popular and is commonly used as a local oscillator in radio

receivers. It has two main advantages viz., adaptability to a wide range of frequencies and is easy to

tune.

The RF transmitter is built around the common passive and active components, which are

very is to obtain from the material shelf. The circuit works on Very High Frequency band with wide

covering range.


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CIRCUIT DIAGRAM OF RF TRANSMITTER

CIRCUIT DESCRIPTION:

The ASIC Transmitter IC has four inputs and only one output pin. The four inputs are for the

frequency range of 17 KHz, 19 KHz, 22 KHz and 25 KHz and four switches are provided for each

range. When any one switch is selected, that frequency is added to the Transmitter circuit as data

frequency and transmitted in the air. The Crystal X1 with two coupling capacitor provides the

working oscillator frequency to the circuit. The Capacitors C6 and C7 are to stabilize the crystal

oscillator frequency.

R

R4

C5

R3

R

C7

CT

C3C4

L1

L2

T2

R

+Vc

Gnd

17 KHz

S1

19KHz

S2ASIC

C6X


32/55



The ASIC output is added to the transmitter circuits oscillator transistor T1s base. The data

frequency is added with carrier frequency 147 MHz and aired for transmitting purpose. The

transistor T1 is heart of the Hartely Oscillator and oscillates at carrier frequency of 147 MHz along

with tuned circuit formed by coil L1 and capacitor C4. The Data frequency is fed to T1 on

base through resistors R4 and R5. Capacitors C1 and C3 and for stabilizing the tuned circuit along

with resistor R3.

To increase the range of the circuit, transmitting signals must be strong enough to travel the

long distance [i.e., upto 100 meters in this prototype]. So the generated signals are made strong by

amplifying to certain level with the help of Transistor T2 and associated circuit.

The Radio frequency thus generated is fed to pre-amplifier transistor T2 on base terminal.

The resistor R6 provides the bias voltage to T2 and capacitors C5 & C7 removes the noise and

harmonics present in the circuit. The antenna coil L2 transmits the radio frequency in the

3.6.3 RF RECEVER MODULE


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CIRCUIT DIAGRAM OF RF RECEIVER

RF RECEIVER

This circuit is built around the ASIC i.e., Application Specific Integrated Circuit, hence less

circuitry is observed. The Radio Frequency tuned circuit has 147 M Hz carrier frequency with four

options viz., 17Khz, 19Khz, 22KHz and 25KHz.

The transmitted signals are received on coil L1 which acts as receiver antenna. The oscillator

transistor removes the received signals from 147MHz carrier frequency and fed to ASIC. The tank

circuit formed by C1 and L1 gives the carrier frequency range. The current limiting resistor R1 and

bypass capacitor C5 stabilizes the oscillator. The resistor R2, R3 and R4 provide the biasing voltage

to the oscillator transistor T1. Capacitors C2 and C3 are there to bypass the noise and harmonicspresent in the received signals. Through coupling capacitor C7 output of the RF Receiver is fed to

ASIC.

The ASIC manipulates the received signal and gives out four channels as output viz., 17

KHz, 19KHz, 22KHz and 25KHz. Each channel is amplified by pre-amplifier transistor T2 along

with bias resistor R9. The output of the pre-amplifier transistor is fed to relay driver stage to activate

T

T

T

TT

T

C

C2

R

R

C

T1

ASIC

R4 R5

R6

R7R9

R9


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the respective relay ON. The Darlington pair T3 and T4 are arranged in driver stage to drive the low

impedance relay.

3.6.4 TELESCOPIC ANTENNA:-

A telescopic antenna is collapsible. It is a series of small diameter tubes of 6 to 8 inches in

length nested one inside the other. The antenna ca be extended to its full length or retracted to a

small length for storage of portability.

Radio antennas are optimally sized based upon wavelength of the frequency they are expected to

"see" . Even multiples of wave length are also used for antennas to minimize there length. i.e. ( 1/2

or 1/4 wavelength)

Antenna wave length (lambda) is base on the speed (c) that a radio signal travels which is about

3x10^8 m/s (300000000 m/s) divided by the frequency(f)

lambda=c/f

Frequencies in the hertz range would have wavelengths in the 1000's of kilometers range. So

any practical length antenna (2 or 3 feet in Length) would work just as well as a larger 5 to 10 foot

antenna as the wavelength is so large.

Fig. Telescopic Antenna


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3.6.5 Loop Antenna

A loop antenna is a radio antenna consisting of a loop (or loops) of wire, tubing, or other

electrical conductor with its ends connected to a balanced transmission line. Within this physical

description there are two very distinct antenna designs: the small loop with a size muchsmaller than

a wavelength, and the resonant loop antenna with a circumference approximately equal to the

wavelength.

Small loops have a poor efficiency and are mainly used as receiving antennas at low

frequencies. Except for car radios, almost every AM broadcast receiver sold has such an antenna

built inside of it or directly attached to it. These antennas are also used forradio direction finding.

Resonant loop antennas are less common. They are typically used at higher frequencies, especially

VHF and UHF, where their size is manageable. They can be viewed as a modification of the folded

dipole antenna and have somewhat similar characteristics. Although the loop may be in the shape of

a circle, distorting it into a somewhat different closed shape does not qualitatively alter its

characteristics in a resonant loop antenna the most important characteristic, resonant frequency, is

determined by the circumference of the loop. For a given loop area, the length of the conductor is

minimized in the case of a circle, making that shape optimum for small loops. Loop antenna use

coupling coils for inductive transmission systems including LF and HF RFID tags and readers.Although these do use radio frequencies, and involve the use of small loops which may be physically

indistinguishable from the small loop antennas discussed here, such systems are not designed to

transmit radio waves. They are near field systems involving alternating magnetic fields only, and

may be analyzed as poorly coupledtransformer windings; their performance criteria are dissimilar to

radioantennas as discussed here.
http://en.wikipedia.org/wiki/Antenna_%28radio%29http://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Balanced_linehttp://en.wikipedia.org/wiki/Transmission_linehttp://en.wikipedia.org/wiki/Electrically_shorthttp://en.wikipedia.org/wiki/Electrically_shorthttp://en.wikipedia.org/wiki/Resonanthttp://en.wikipedia.org/wiki/Antenna_gain#Efficiencyhttp://en.wikipedia.org/wiki/AM_broadcasthttp://en.wikipedia.org/wiki/Radio_direction_findinghttp://en.wikipedia.org/wiki/Folded_dipolehttp://en.wikipedia.org/wiki/Folded_dipolehttp://en.wikipedia.org/wiki/RFIDhttp://en.wikipedia.org/wiki/Near_and_far_fieldhttp://en.wikipedia.org/wiki/Transformerhttp://en.wikipedia.org/wiki/Antenna_%28radio%29http://en.wikipedia.org/wiki/Antenna_%28radio%29http://en.wikipedia.org/wiki/Transformerhttp://en.wikipedia.org/wiki/Near_and_far_fieldhttp://en.wikipedia.org/wiki/RFIDhttp://en.wikipedia.org/wiki/Folded_dipolehttp://en.wikipedia.org/wiki/Folded_dipolehttp://en.wikipedia.org/wiki/Radio_direction_findinghttp://en.wikipedia.org/wiki/AM_broadcasthttp://en.wikipedia.org/wiki/Antenna_gain#Efficiencyhttp://en.wikipedia.org/wiki/Resonanthttp://en.wikipedia.org/wiki/Electrically_shorthttp://en.wikipedia.org/wiki/Electrically_shorthttp://en.wikipedia.org/wiki/Transmission_linehttp://en.wikipedia.org/wiki/Balanced_linehttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Antenna_%28radio%29


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3.7 MICRO CONTROLLER

The field parameters are monitored by this Microcontroller chip with the help of user written

program and generates alert message for LCD display and fault code for remote monitoring end

transmission. The Microcontroller Chip has input port for getting fault condition of field parametersand Stop signal through RF Receiver and output port for sending fault code to DTMF Encoder and

switching Relay [MCB] for isolating power line from load.

3.7.1 INTRODUCTION OF MICRO-CONTROLLER

What is a microcontroller?

The general definition of a microcontroller is a single chip computer, which refers to the factthat they contain all of the functional sections (CPU, RAM, ROM, I/O, ports and timers) of a

traditionally defined computer on a single integrated circuit. Some experts even describe them as

special purpose computers with several qualifying distinctions that separate them from other

computers.

Microcontrollers are "embedded" inside some other device (often a consumer product) so

that they can control the features or actions of the product. Another name for a microcontroller,

therefore, is "embedded control ler."

Microcontrollers are dedicated to one task and run one specific program. The program is

stored in ROM (read-only memory) and generally does not change.

Microcontrollers are often low-power devices. A desktop computer is almost always plugged

into a wall socket and might consume 50 watts of electricity. A battery-operated microcontroller

might consume 50 mill watts.

A microcontroller has a dedicated input device and often (but not always) has a small LED or

LCD display for output. A microcontroller also takes input from the device it is controlling and

controls the device by sending signals to different components in the device.

A microcontroller is often small and low cost. The components are chosen to minimize size

and to be as inexpensive as possible.


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A microcontroller is often, but not always, ruggedized in some way. The microcontroller

controlling a car's engine, for example, has to work in temperature extremes that a normal computer

generally cannot handle. A car's microcontroller in Kashmir regions has to work fine in -30 degree F

(-34 C) weather, while the same microcontroller in Gujarat region might be operating at 120

degrees F (49 C). When you add the heat naturally generated by the engine, the temperature can go

as high as 150 or 180 degrees F (65-80 C) in the engine compartment. On the other hand, a

microcontroller embedded inside a VCR hasn't been ruggedized at all.

Clearly, the distinction between a computer and a microcontroller is sometimes blurred.

Applying these guidelines will, in most cases, clarify the role of a particular device.

Why are they so popular?

The programmability of modern desktop PCs makes them extraordinarily versatile. The

functionality of the entire machine can be altered by merely changing its programming.

Microcontrollers share this attribute with their desktop relatives. The chips are manufactured with

powerful capabilities and the end user determines exactly how the device will function. Often, this

makes a dramatic difference in the cost and complexity of a particular design. The true impact of this

statement is best illustrated by example.

For every clock pulse, the circuit produces one of the three bit numbers in the sequence 000,

100, 111, 010, 011. This design has been implemented with three flip-flops and seven discrete gates

as well as a significant amount of wiring.

The design of this system can be quite laborious. One must begin with a state graph followed

by a state table. Then, the flip-flop T input equations must be derived from a set of Karnaugh maps.

Next, the t input equations must be transformed into the actual T input network. All of this circuitry

must then be wired together; a task that's time consuming and sometimes error prone. On the otherhand, this can be accomplished with a simpler, less costly microcontroller design. Notice the

dramatic difference in the amount of hardware and wiring. This simple circuit, along with about a

dozen lines of code, will perform the same task as the first circuit. There are other benefits as well.

The microcontroller implementation does not have to contend with the undetermined states that

sometimes occur with discrete designs. Also consider for a moment what would be required to


38/55



change the sequence of numbers in the first circuit. What if the output needs to be changed

to eight bits instead of three? These are trivial modifications for the microcontroller while the

discrete circuit would require a complete redesign.

The example above is not an obscure case. The effects of this device are being felt in almostevery facet of digital design. A sure method of determining the popularity of an electronic device is

to note when they attain widespread use by hobbyists. It therefore becomes essential that the

electronics engineer or hobbyist learn to program these microcontrollers to maintain a level of

competence and to gain the advantages microcontrollers provide in his or her own circuit designs.


39/55



CIRCUIT DIAGRAM [MOTHER BOARD] OF 89C51


40/55



CIRCUIT DESCRIPTION

The mother board of 89C51 has following sections: Power Supply, 89C51 IC, Oscillator,

Reset Switch & I/O ports. Let us see these sections in detail.

POWER SUPPLY:

This section provides the clean and harmonic free power to IC to function properly. The

output of the full wave rectifier section, which is built using two rectifier diodes, is given to filter

capacitor. The electrolytic capacitor C1 filters the pulsating dc into pure dc and given to Vin pin-1 of

regulator IC 7805.This three terminal IC regulates the rectified pulsating dc to constant +5 volts. C2

& C3 provides ground path to harmonic signals present in the inputted voltage. The Vout pin-3 gives

constant, regulated and spikes free +5 volts to the mother board.

The allocation of the pins of the 89C51 follows a U-shape distribution. The top left hand

corner is Pin 1 and down to bottom left hand corner is Pin 20. And the bottom right hand corner is

Pin 21 and up to the top right hand corner is Pin 40. The Supply Voltage pin Vcc is 40 and ground

pin Vss is 20.

OSCILLATOR:

If the CPU is the brain of the system then the oscillator, or clock, is the heartbeat. It provides

the critical timing functions for the rest of the chip. The greatest timing accuracy is achieved with a

crystal or ceramic resonator. For crystals of 2.0 to 12.0 MHz, the recommended capacitor values

should be in the range of 15 to 33pf2.

Across the oscillator input pins 18 & 19 a crystal x1 of 4.7 MHz to 20 MHz value can be connected.

The two ceramic disc type capacitors of value 30pF are connected across crystal and ground,

stabilizes the oscillation frequency generated by crystal.


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I/O PORTS:

There are a total of 32 i/o pins available on this chip. The amazing part about these ports is

that they can be programmed to be either input or output ports, even "on the fly" during operation!

Each pin can source 20 mA (max) so it can directly drive an LED. They can also sink a maximum

of 25 Ma current.

Some pins for these I/O ports are multiplexed with an alternate function for the peripheral features

on the device. In general, when a peripheral is enabled, that pin may not be used as a general purpose

I/O pin. The alternate function of each pin is not discussed here, as port accessing circuit takes care

of that.

This 89C51 IC has four I/O ports and is discussed in detail:P0.0 TO P0.7

PORT0 is an 8-bit [pins 32 to 39] open drain bi-directional I/O port. As an output port, each pin can

sink eight TTL inputs and configured to be multiplexed low order address/data bus then has internal

pull ups. External pull ups are required during program verification.

P1.0 TO P1.7

PORT1 is an 8-bit wide [pins 1 to 8], bi-directional port with internal pull ups. P1.0 and P1.1 can be

configured to be the timer/counter 2 external count input and the timer/counter 2 trigger input

respectively.

P2.0 TO P2.7

PORT2 is an 8-bit wide [pins 21 to 28], bi-directional port with internal pull ups. The PORT2 output

buffers can sink/source four TTL inputs. It receives the high-order address bits and some control

signals during Flash programming and verification.

P3.0 TO P3.7

PORT3 is an 8-bit wide [pins 10 to 17], bi-directional port with internal pull ups. The Port3 output

buffers can sink/source four TTL inputs. It also receives some control signals for Flash programming

and verification.


42/55



PSEN Program Store Enable [Pin 29] is the read strobe to external program memory. ALE Address

Latch Enable [Pin 30] is an output pulse for latching the low byte of the address during accesses to

external memory.

EA External Access Enable [Pin 31] 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.

RSTReset input [Pin 9] must be made high for two machine cycles to resets the devices oscillator.

The potential difference is created using 10MFD/63V electrolytic capacitor and 20K Ohm resistor

with a reset switch.

3.8 LCD MODULE

LCDs can add a lot to any application in terms of providing an useful interface for the user,

debugging an application or just giving it a "professional" look. The most common type of LCD

controller is the Hitatchi 44780 which provides a relatively simple interface between a processor and

an LCD. Using this interface is often not attempted by inexperienced designers and programmers

because it is difficult to find good documentation on the interface, initializing the interface can be a

problem and the displays themselves are expensive.

The most common connector used for the 44780 based LCDs is 14 pins in a row, with pin

centers 0.100" apart. The pins are wired as:

DATA

R/ S

R/ W

E450 nSec

LCD DATA WRITE WAVEFORM


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Pins Description

1 Ground

2 Vcc

3 Contrast Voltage

4 "R/S" _Instruction/Register Select

5 "R/W" _Read/Write LCD Registers

6 "E" Clock

7 -

14

Data I/O Pins

The interface is a parallel bus, allowing simple and fast reading/writing of data to and from

the LCD.

The LCD Data Write Waveform will write an ASCII Byte out to the LCD's screen. The

ASCII code to be displayed is eight bits long and is sent to the LCD either four or eight bits at a

time. If four bit mode is used, two "nibbles" of data (Sent high four bits and then low four bits with

an "E" Clock pulse with each nibble) are sent to make up a full eight bit transfer. The "E" Clock is

used to initiate the data transfer within the LCD.

Sending parallel data as either four or eight bits are the two primary modes of operation.

While there are secondary considerations and modes, deciding how to send the data to the LCD is

most critical decision to be made for an LCD interface application.


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The different instructions available for use with the 44780 are shown in the table below:

R/S R/W D7 D6 D5 D4 D3 D2 D1 D0 Instruction/Description

4 5 14 13 12 11 10 9 8 7 Pins

0 0 0 0 0 0 0 0 0 1 Clear Display

0 0 0 0 0 0 0 0 1 * Return Cursor and LCD to Home Position

0 0 0 0 0 0 0 1 ID S Set Cursor Move Direction

0 0 0 0 0 0 1 D C B Enable Display/Cursor

0 0 0 0 0 1 SC RL * * Move Cursor/Shift Display

0 0 0 0 1 DL N F * * Set Interface Length

0 0 0 1 A A A A A A Move Cursor into CGRAM

0 0 1 A A A A A A A Move Cursor to Display

0 1 BF * * * * * * * Poll the "Busy Flag"

1 0 D D D D D D D D Write a Character to the Display at the

Current Cursor Position

1 1 D D D D D D D D Read the Character on the Display at the

Current Cursor Position

The bit descriptions for the different commands are: "*" - Not Used/Ignored. This bit can be either

"1" or "0"

Most LCD displays have a 44780 and support chip to control the operation of the LCD. The

44780 is responsible for the external interface and provides sufficient control lines for sixteen

characters on the LCD. The support chip enhances the I/O of the 44780 to support up to 128

characters on an LCD. From the table above, it should be noted that the first two entries ("8x1",

"16x1") only have the 44780 and not the support chip. This is why the ninth character in the 16x1

does not "appear" at address 8 and shows up at the address that is common for a two line LCD.

The Character Set available in the 44780 is basically ASCII. It is "basically" because some

characters do not follow the ASCII convention fully (probably the most significant difference is

0x05B or "\" is not available). The ASCII Control Characters (0x008 to 0x01F) do not respond as

control characters and may display funny (Japanese) characters.


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Experts typically use a potentiometer wired as a voltage divider. This will provide an easily

variable voltage between Ground and Vcc, which will be used to specify the contrast (or "darkness")

of the characters on the LCD screen. You may find that different LCDs work differently with lower

voltages providing darker characters in some and higher voltages do the same thing in others.

LCD Contrast Circuit

+Vcc

Pin-3 Contrast

LCD10K pot

Shift Register LCD Data Write

R6

D0D1

Dn

E

LCD

E Clock

S/R

Processor

Data

Data

Clock0

0


46/55



Liquid crystal panel service life 100,000 hours minimum at 25oC -10

oC

sumption becomes three times higher than initial value

Safety

the liquid crystal

touches your skin or clothes, wash it off immediately using soap and plenty of water.

Handling

frame from the module.

Mounting and Design

placing transparent plates (e.g.

acrylic or glass) on the display surface, frame, and polarizing plate

-supply voltage is applied.

transparent electrodes may break.

Storage

oC - 10

oC and the humidity below

65% RH.


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3.8.1 LCD BASIC

A liquid crystal display (LCD) is a thin, flat display device made up of any number of color

or monochrome pixels arrayed in front of a light source or reflector. Each pixel consists of a column

of liquid crystal molecules suspended between two transparent electrodes, and two polarizing filters,

the axes of polarity of which are perpendicular to each other. Without the liquid crystals between

them, light passing through one would be blocked by the other. The liquid crystal twists the

polarization of light entering one filter to allow it to pass through the other.

Many microcontroller devices use 'smart LCD' displays to output visual information. LCD

displays designed around Hitachi's LCD HD44780 module, are inexpensive, easy to use, and it is

even possible to produce a readout using the 8x80 pixels of the display. They have a standard ASCII

set of characters and mathematical symbols.

For an 8-bit data bus, the display requires a +5V supply plus 11 I/O lines. For a 4-bit data bus

it only requires the supply lines plus seven extra lines. When the LCD display is not enabled, data

lines are tri-state and they do not interfere with the operation of the microcontroller.

Fig.4.1: A typical LCD

3.8.2 Signals to the LCD

The LCD also requires 3 control lines from the microcontroller: Enable (E)

This line allows access to the display through R/W and RS lines. When this line is low, the LCD is

disabled and ignores signals from R/W and RS. When (E) line is high, the LCD checks the state of

the two control lines and responds accordingly.


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Pin description

Most LCDs with 1 controller has 14 Pins and LCDs with 2 controller has 16 Pins (two pins

are extra in both for back-light LED connections)

Fig.4.2 Pindiagramof 2x16lineLCD

Pin Details

Table: 4.1


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3.9 BUZZER AND BUTTON INTERFACE

3.9.1 Buzzer

This is a small 12mm round buzzer that operates around the audible 2kHz range. We drove it

directly from a 5V Controller to generate the tones for our Simon demonstration game. Use buzzers

to create simple music or user interfaces.

Fig:.1 HDX

Button interface:

The Button Interface module provides you with a set of programmable buttons that can be

made to create and reset variables when clicked.

There is a Push button used in our project which basically used to reset the Microcontroller.

A push-button is a simple switch mechanism for controlling some aspect of a machine or a process.

The surface is usually flat or shaped to accommodate the human finger or hand, so as to be easily

depressed or pushed.

Fig:.2 Button


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CHAPTER 4

SOFTWARE REQUIREMENTS

The software we have used in our project is C and C-Graphics. This software is user

friendly and can be programmed in easy way. In our project we had used this software because it caneasily read the signals from the parallel port and display the consequences.

The KEIL is a software package, which is a part of an Embedded C. This is used to

program the microcontroller. The KEIL program which executed will generate .hex file that is used

to program the microcontroller. The starting address from which the code has to be transferred can

be changed and selected by the user.

The KEIL software helps to make the programming easy. The hex-codes can be transferred

into the microcontroller by using a serial bus RS-232. The microcontroller has a program in its

internal ROM and when executed will receive the data from the RS-232 that is connected to the

serial port or mouse port of a computer.

The MicroVision4 IDE from KEIL software, combines project management, make facilities,

source code editing, program debugging and complete simulation in one power environment.

MicroVision2 helps you get program work faster than while providing an easy use development

platform. The editor and debugger are integrated into a single application and provide a flawless

embedded project development environment.

The microcontroller has been programmed using KEIL software. The program is written in

the KEIL software and then executed. The software will provide .hex file. The .hex file will consist

of hexadecimal codes, which are the op-codes that have to be coded into the microcontroller. By

interfacing the computer and the microcontroller with RS-232 bus, we can download, the hex codes

into the microcontroller from away address. This codes when executed provides the output, which is

required by the programmer.

Hence the difficulty of the assembly language programming has been replaced with KEIL

high-level-language, which is easy to program.


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CHAPTER 5

APPLICATION

For test rig security areas especially in fighter aircraft.

It can be used in industries for security purposes

It can be used in homes


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CHAPTER 6

Advantage & Limitation6.1Advantage

It is easy to use

This provides a high level of security

By using this, the manual error is reduced

It alerts the operator who is at the control room and intruder who is entering the test rig area

The concern person is alerted when there is any deviation from the normal condition using

pager device

6.2 Limitation There are some chances of false alarming

Distance is reduced


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CHAPTER 7

CONCLUSION

In todays world security is needed in almost all the field. Large number of accidents occurs

in the industries due to negligence and lack of security in this project, we have included the alarm

system to intimate both trespasser and the operator at the control room, This concept is quite

efficient because we can monitor it any where


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CHAPTER 8

FUTURE ENHANCEMENTS

This project can be used in many others scenarios to measure other different parameters such

as temperature, humidity, smoke etc..also by using visual basic(VB),we can enhance the graphical

representation of various system parameters

Instead of using RF transceiver, we can use GSM modem for communication purpose

Date post:	02-Jun-2018
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Test Rig Security & Monitoring System

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