Sensor

MINI PROJECT REPORT 2011 PIR SENSOR BASED SECURITY SYSTEM

INTRODUCTION

DEPT. OF ELECTRONICS & INSTRUMENTATION Page 1


INTRODUCTION

Security is one of the major concerns of the present century. Many technologies are employed to tackle the burglars or house breakers. The most commonly used security systems like infrared and sound sensors have the disadvantage of particular line of sight and reliability. Having a wireless alarm system in your home is definitely the best way to protect your family and your home from possible break-ins. It doesn’t take a lot of time to install and they work on batteries.

A Passive Infrared sensor (PIR sensor) is an electronic device that measures infrared (IR) light radiating from objects in its field of view. PIR sensors are often used in the construction of PIR-based motion detectors . Apparent motion is detected when an infrared source with one temperature, such as a human, passes in front of an infrared source with another temperature, such as a wall.

All objects above absolute zero emit energy in the form of radiation. It is usually infrared radiation that is invisible to the human eye but can be detected by electronic devices designed for such a purpose. The term passive in this instance means that the PIR device does not emit an infrared beam but merely passively accepts incoming infrared radiation. “Infra” meaning below our ability to detect it visually, and “Red” because this color represents the lowest energy level that our eyes can sense before it becomes invisible. Thus, infrared means below the energy level of the color red, and applies to many sources of invisible energy.


http://en.wikipedia.org/wiki/Human_eye

http://en.wikipedia.org/wiki/Absolute_zero

http://en.wikipedia.org/wiki/Wall

http://en.wikipedia.org/wiki/Human

http://en.wikipedia.org/wiki/Temperature

http://en.wikipedia.org/wiki/Motion_detector

http://en.wikipedia.org/wiki/Infrared

http://en.wikipedia.org/wiki/Electronic_device


BLOCK DIAGRAM



BLOCK DIAGRAM


COMPARATORCOMPARATOR




BLOCK DIAGRAM DESCRIPTION

1. SENSOR SECTION

i) PIR SENSOR

A Passive Infrared Sensor (PIR) is an electronic device that measures infrared (IR) light radiating from objects in its field of view. It is a human body sensor. The sensor senses the passive infrared radiation from the human body and produces an output. The current thus produced is very low & need to be amplified.

ii) TWO STAGE AMPLIFIER

The output voltage produced by the PIR sensor is very low & hence need to be amplified. For this purpose it is fed into a 2 stage amplifier. Here we amplifies the voltage in two stages using an op amp circuit. The range of the sensor depends upon the gain of the amplifier.

iii) COMPARATOR

Comparator is a circuit which compares the input voltage (output from the amplifier) with a fixed reference voltage and produces an output.

iv) TRANSISTOR SWITCH

When the transistor is working as a switch, cut off and saturation regions are the stable regions of its operation; while active region is the unstable region if its operation. The current from the comparator is very low & is amplified in this section.

v) BISTABLE MULTIVIBRATOR

Here we use IC CD4017 as the bi-stable multivibrator . It is a decade counter. As we know a bi-stable multivibrator has two stable states we take the output from second & third pins and reset the fourth pin.

iv) RELAY UNIT



It is an electromechanical switch. It is a 12V supply to switch a 230V supply. The relay used is a 12V, 200ohm, 6A relay.

2. TRANSMITTER SECTION

i) ENCODER

The output from Bi-stable multivibrator is given to the data in of the encoder.

It transmits the 4bit data serially.

ii) ASK TRANSMITTER

The output data from the encoder is given to the ASK transmitter. The transmitter allows the data from the encoder to be modulated at a frequency of

433MHz & is transmitted via a transmitting antenna.

3. POWER SUPPLY

All the electronic circuits require a dc electric source for energising; such a dc energy source is derived from our landline high power supply. Initially the line supply is step down by a step down transformer, and then a bridge rectifier rectifies it. The output of the rectifier is rippled dc; this rippled dc is smoothened by using filter capacitor or by capacitor filter.

4. RECEIVER SECTION

i) ASK RECEIVER

Here we use an ASK receiver whose frequency is same as that of the ASK transmitter i.e., 433MHz. The signal from the antenna (i.e. the 8 bit address and 4 bit serial data) is received by the ASK receiver.

ii) DECODER

Here we use HT 12D as the decoder. The received data which is to be decoded is given as the input of the decoder. The decoder converts 4bit serial data into parallel data.

iii) TRANSISTOR SWITCH



The output of the decoder is very small (about +5V) i.e., it doesn’t produces enough current to drive the buzzer. So we use a transistor switch which amplifies the current thus making it capable to drive the buzzer.

iv) BUZZER

Buzzer circuit converts the electrical signal received to voice signal thus producing a sound or alarm for alert.



CIRCUIT DIAGRAM











CIRCUIT DESCRIPTION



1.SENSOR CIRCUIT

PASSIVE INFRARED RADIAL SENSOR

A Passive Infrared sensor (PIR sensor) is an electronic device that

measures infrared (IR) light radiating from objects in its field of view. PIR

sensors sets in front of an infrared source with another temperature, such as

a wall.

All objects above absolute zero emit energy in the form of radiation. It is usually

infrared radiation that is invisible to the human eye but can be detected by

electronic devices designed for such a purpose. The term passive in this instance

means that the PIR device does not emit an infrared beam but merely passively

accepts incoming infrared radiation. “Infra” meaning below our ability to detect

it visually, and “Red” because this color represents the lowest energy level that

our eyes can sense before it becomes invisible. Thus, infrared means below the

energy level of the color red, and applies to many sources of invisible energy.

Design

Infrared radiation enters through the front of the sensor, known as the sensor

face. At the core of a PIR sensor is a solid state sensor or set of sensors, made

from an approximately 1/4inch square of natural or artificial pyroelectric

materials, usually in the form of a thin film, out of gallium

nitride (GaN), caesium nitrate (CsNO3), polyvinyl fluorides, derivatives of

phenylpyrazine, and cobalt phthalocyanine. (See pyroelectric crystals.) Lithium



tantalate (LiTaO3) is a crystal exhibiting both piezoelectric and pyroelectric

properties.

The sensor is often manufactured as part of an integrated circuit and may consist

of one (1), two (2) or four (4) 'pixels' of equal areas of the pyroelectric material.

Pairs of the sensor pixels may be wired as opposite inputs to a differential

amplifier. In such a configuration, the PIR measurements cancel each other so

that the average temperature of the field of view is removed from the electrical

signal; an increase of IR energy across the entire sensor is self-cancelling and

will not trigger the device. This allows the device to resist false indications of

change in the event of being exposed to flashes of light or field-wide

illumination. (Continuous bright light could still saturate the sensor materials

and render the sensor unable to register further information.) At the same time,

this differential arrangement minimizes common-mode interference, allowing

the device to resist triggering due to nearby electric fields. However, a

differential pair of sensors cannot measure temperature in that configuration and

therefore this configuration is specialized for motion detectors, see below.

PIR-based motion detector

Directional Infrared Radial Sensor

Excellent performance infrared sensor for use in alarm burglar systems,

visitor presence monitoring, light switches and robots. Narrow detection beam

for use in hallway and defined area detection systems.

Features

Dual Compensating Elements

Excellent Operating Stability

Supply Voltage: 3-15V

Narrow Sense Window for Directional Sensing

Body Dimensions: 9.1mm Diameter, 4.5mm High excluding pins, Pins -



13.5mm.

Fresnel Lens

Fresnel Lens to suit above PIR Sensors. Designed for white light immunity

and uniform sensitivity from any angle. Inexpensive and easy to use.

Features

Designed for Use with above Sensors

Optimized for Dual Element Pyroelectric Devices

White Light Immunity to Reduce False Triggers

UV Resistant for Outdoor Applications

Designed for Uniform Sensitivity to Reduce Electronic Gain

2.OPERATIONAL AMPLIFIER

An operational amplifier ("op-amp") is a DC-coupled high-gain electronic

voltage amplifier with a differential input and, usually, a single-ended

output. An op-amp produces an output voltage that is typically hundreds of

thousands times larger than the voltage difference between its input terminals.

Operational amplifiers are important building blocks for a wide range of

electronic circuits. They had their origins in analog computers where they were

used in many linear, non-linear and frequency-dependent circuits. Their



popularity in circuit design largely stems from the fact the characteristics of the

final elements (such as their gain) are set by external components with little

dependence on temperature changes and manufacturing variations in the op-amp

itself. The op-amp is one type of differential amplifier. Other types of

differential amplifier include the fully differential amplifier (similar to the op-

amp, but with two outputs), the instrumentation amplifier (usually built from

three op-amps), the isolation amplifier (similar to the instrumentation amplifier,

but with tolerance to common-mode voltages that would destroy an ordinary op-

amp), and negative feedback amplifier (usually built from one or more op-amps

and a resistive feedback network).

Circuit notation

Circuit diagram symbol for an op-amp

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

: non-inverting input

: inverting input

: output

: positive power supply

: negative power supply

The power supply pins ( and ) can be labelled in different ways (See IC

power supply pins). Despite different labelling, the function remains the same


http://en.wikipedia.org/wiki/File:Op-amp_symbol.svg

http://en.wikipedia.org/wiki/File:Op-amp_symbol.svg


— to provide additional power for amplification of the signal. Often these pins

are left out of the diagram for clarity, and the power configuration is described

or assumed from the circuit.

Operation

The amplifier's differential inputs consist of a input and a input, and

ideally the op-amp amplifies only the difference in voltage between the two,

which is called the differential input voltage. The output voltage of the op-amp

is given by the equation,

where is the voltage at the non-inverting terminal is, is the voltage

at the inverting terminal and AOL is the open-loop gain of the amplifier.

(The term "open-loop" refers to the absence of a feedback loop from the

output to the input.)

Typically the op-amp's very large gain is controlled by negative feedback,

which largely determines the magnitude of its output ("closed-loop") voltage

gain in amplifier applications, or the transfer function required (in analog

computers). Without negative feedback, and perhaps with positive

feedback for regeneration, an op-amp acts as a comparator. High

input impedance at the input terminals and low output impedance at the output

terminal(s) are important typical characteristics.


http://en.wikipedia.org/wiki/File:Operational_amplifier_noninverting.svg


With no negative feedback, the op-amp acts as a comparator. The inverting

input is held at ground (0 V) by the resistor, so if the V in applied to the non-

inverting input is positive, the output will be maximum positive, and if V in is

negative, the output will be maximum negative. Since there is no feedback from

the output to either input, this is an open loop circuit. The circuit's gain is just

the GOL of the op-amp.

Adding negative feedback via the voltage divider Rf,Rg reduces the gain.

Equilibrium will be established when Vout is just sufficient to reach around and

"pull" the inverting input to the same voltage as V in. As a simple example, if

Vin = 1 V and Rf = Rg, Vout will be 2 V, the amount required to keep V– at 1 V.

Because of the feedback provided by Rf,Rg this is a closed loop circuit. Its over-

all gain Vout / Vin is called the closed-loop gain ACL. Because the feedback is

negative, in this case ACL is less than the AOL of the op-amp.

The magnitude of AOL is typically very large—10,000 or more for integrated

circuit op-amps—and therefore even a quite small difference between and

drives the amplifier output nearly to the supply voltage. This is

called saturation of the amplifier. The magnitude of AOL is not well controlled

by the manufacturing process, and so it is impractical to use an operational

amplifier as a stand-alone differential amplifier. If predictable operation is

desired, negative feedback is used, by applying a portion of the output voltage to

the inverting input. The closed loop feedback greatly reduces the gain of the

amplifier. If negative feedback is used, the circuit's overall gain and other

parameters become determined more by the feedback network than by the op-


http://en.wikipedia.org/wiki/File:Op-amp_open-loop_1.svg


amp itself. If the feedback network is made of components with relatively

constant, stable values, the unpredictability and inconstancy of the op-amp's

parameters do not seriously affect the circuit's performance.

If no negative feedback is used, the op-amp functions as a switch or comparator.

Positive feedback may be used to introduce hysteresis or oscillation.

Ideal and real op-amps

An equivalent circuit of an operational amplifier that models some resistive non-

ideal parameters.

An ideal op-amp is usually considered to have the following properties, and they

are considered to hold for all input voltages:

Infinite open-loop gain (when doing theoretical analysis, a limit may be

taken as open loop gain AOL goes to infinity).

Infinite voltage range available at the output (vout) (in practice the voltages

available from the output are limited by the supply voltages and ).

The power supply sources are called rails.

Infinite bandwidth (i.e., the frequency magnitude response is considered

to be flat everywhere with zero phase shift).


http://en.wikipedia.org/wiki/File:Op-Amp_Internal.svg

http://en.wikipedia.org/wiki/File:Op-Amp_Internal.svg


Infinite input impedance (so, in the diagram, , and zero current

flows from to ).

Zero input current (i.e., there is assumed to be no leakage or bias current

into the device).

Zero input offset voltage (i.e., when the input terminals are shorted so that

, the output is a virtual ground or vout = 0).

Infinite slew rate (i.e., the rate of change of the output voltage is

unbounded) and power bandwidth (full output voltage and current

available at all frequencies).

Zero output impedance (i.e., Rout = 0, so that output voltage does not vary

with output current).

Zero noise.

Infinite Common-mode rejection ratio (CMRR).

Infinite Power supply rejection ratio for both power supply rails.

In practice, none of these ideals can be realized, and various shortcomings and

compromises have to be accepted. Depending on the parameters of interest, a

real op-amp may be modelled to take account of some of the non-infinite or

non-zero parameters using equivalent resistors and capacitors in the op-amp

model. The designer can then include the effects of these undesirable, but real,

effects into the overall performance of the final circuit. Some parameters may

turn out to have negligible effect on the final design while others represent

actual limitations of the final performance that must be evaluated.



Basic single stage amplifiers

Non-inverting amplifier

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

In a non-inverting amplifier, the output voltage changes in the same direction as

the input voltage.

The gain equation for the op-amp is:

However, in this circuit V– is a function of Vout because of the negative feedback

through the R1R2 network. R1 and R2 form a voltage divider, and as V– is a high-

impedance input, it does not load it appreciably. Consequently:

where

Substituting this into the gain equation, we obtain:

Solving for Vout:


http://en.wikipedia.org/wiki/File:Op-Amp_Non-Inverting_Amplifier.svg


If AOL is very large, this simplifies to

.

Inverting amplifier

An op-amp connected in the inverting amplifier configuration

In an inverting amplifier, the output voltage changes in an opposite direction to

the input voltage.

As for the non-inverting amplifier, we start with the gain equation of the op-

amp:

This time, V– is a function of both Vout and Vin due to the voltage divider formed

by Rf and Rin. Again, the op-amp input does not apply an appreciable load, so:

Substituting this into the gain equation and solving for Vout:


http://en.wikipedia.org/wiki/File:Op-Amp_Inverting_Amplifier.svg


If AOL is very large, this simplifies to

.

A resistor is often inserted between the non-inverting input and ground (so both

inputs "see" similar resistances), reducing the input offset voltage due to

different voltage drops due to bias current, and may reduce distortion in some

op-amps.

A DC-blocking capacitor may be inserted in series with the input resistor when

a frequency response down to DC is not needed and any DC voltage on the

input is unwanted. That is, the capacitive component of the input impedance

inserts a DC zero and a low-frequency pole that gives the circuit a band

pass or high-pass characteristic.

Positive feedback configurations

Another typical configuration of op-amps is with positive feedback, which takes

a fraction of the output signal back to the non-inverting input. An important

application of it is the comparator with hysteresis, the Schmitt trigger.

Positive voltage level detector

A positive reference voltage Vref is applied to one of the op-amp's inputs. This

means that the op-amp is set up as a comparator to detect a positive voltage. If

the voltage to be sensed, Ei, is applied to op amp's (+) input, the result is a

noninverting positive-level detector. When Ei is above Vref, VO equals +Vsat.

When Ei is below Vref, VO equals -Vsat.



If Ei, is applied to the inverting input, the circuit is an inverting positive-level

detector: When Ei is above Vref, VO equals -Vsat.

Negative voltage level detector

A negative voltage detector is a circuit that detects when input signal E i crosses

the negative voltage -Vref. When Ei is above -Vref, VO equals +Vsat. When Eiis

below -Vref, VO equals -Vsat.When Ei is above -Vref, VO equals -Vsat, and when

Eiis below -Vref, VO equals +Vsat.

Sine to square wave converter

The zero detector will convert the output of a sine-wave from a function

generator into a variable-frequency square wave. If Ei is a sine wave, triangular

wave, or wave of any other shape that is symmetrical around zero, the zero-

crossing detector's output will be square.

Because of the wide slew-range and lack of positive feedback, the response of

all the level detectors described above will be relatively slow. Using a general-

purpose op-amp, for example, the frequency of Ei for the sine to square wave

converter should probably be below 100 Hz.

3. COMPARATOR

LM 324N IC configured as Comparator. The Comparator has two inputs, one is

inverting terminal and other is non-inverting terminal. Fixed reference voltage is

applied to inverting terminal (-ve).and other time varying signal is applied to

non-inverting terminal (+ve).because of this arrangement the circuit is called

Comparator.

When Vin is less than Vref, the output voltage Vo is set –Vsat.

Because the voltage at the –ve input is higher than at the +input. on other hand



when vin is greater than Vref the +ve input becomes positive with respect to –

ve input.,Vo goes to +Vsat thus Vo changes from one saturation level to

another.

4.TRANSISTOR AS A SWITCH

When we use a transistor as a switch, we will be operating it in either an "all

on" or an "all off" mode. Depending on the transistor, we'll just apply some

"maximum" base voltage to drive it into saturation and allow for maximum

collector current, or we'll not apply any base voltage and the device will not be

conducting any current through it. That's the "on and off" of it.

This idea applies to the "standard" transistor. Things change a bit for FETs and

some other devices, but the concept of using the device in an "all on" or "all off"

state is common to the application of all devices acting as switches. We either

turn them "all the way on" or "all the way off" via the base, gate or applicable

terminal of the device.

The Transistor as a Switch

When used as an AC signal amplifier, the transistors Base biasing voltage is

applied so that it always operates within its "active" region that is the linear part

of the output characteristics curves are used. However, both the NPN & PNP

type bipolar transistors can be made to operate as an "ON/OFF" type solid state

switch by biasing its Base differently to that of an amplifier. Solid state switches

are one of the main applications of transistors. Transistor switches are used for

controlling high power devices such as motors, solenoids or lamps, but they can

also be used in digital electronics and logic gate circuits.



If the circuit uses the Bipolar Transistor as a Switch, then the biasing of the

transistor, either NPN or PNP is arranged to operate at the sides of the V-

I characteristics curves we have seen previously. The areas of operation for a

transistor switch are known as the Saturation Region and the Cut-off Region.

This means then that we can ignore the operating Q-point biasing and voltage

divider circuitry required for amplification, and just turn the transistor "fully-

OFF" (cut-off region) or "fully-ON" (saturation region) as shown below.

Operating Regions

The pink shaded area at the bottom of the curves represents the "Cut-off" region

while the blue area to the left represents the "Saturation" region of the transistor.

Both these transistor regions are defined as:



1. Cut-off Region

Here the operating conditions of the transistor are zero input base current ( IB ),

zero output collector current ( IC ) and maximum collector voltage ( VCE ) which

results in a large depletion layer and no current flowing through the device.

Therefore the transistor is switched "Fully-OFF".

Cut-off Characteristics

The input and Base are grounded

(0v)

Base-Emitter voltage VBE < 0.7V

Base-Emitter junction is reverse

biased

Base-Collector junction is

reverse biased

Transistor is "fully-OFF" (Cut-

off region)

No Collector current flows

(IC = 0)

Vout = VCE = VCC = "1"

Transistor operates as an "open

switch"

Then we can define the "cut-off region" or "OFF mode" of a bipolar transistor

switch as being, both junctions reverse biased, IB < 0.7V and IC = 0. For a PNP

transistor, the Emitter potential must be negative with respect to the Base.



2. Saturation Region

Here the transistor will be biased so that the maximum amount of base current is

applied, resulting in maximum collector current resulting in the minimum

collector emitter voltage drop which results in the depletion layer being as small

as possible and maximum current flowing through the transistor. Therefore the

transistor is switched "Fully-ON".

Saturation Characteristics

The input and Base are

connected to VCC

Base-Emitter voltage VBE > 0.7V

Base-Emitter junction is forward

biased

Base-Collector junction is

forward biased

Transistor is "fully-ON"

(saturation region)

Max Collector current flows

(IC = Vcc/RL)

VCE = 0 (ideal saturation)

Vout = VCE = "0"

Transistor operates as a "closed

switch"

Then we can define the "saturation region" or "ON mode" of a bipolar transistor

switch as being, both junctions forward biased, IB > 0.7V and IC = Maximum.



For a PNP transistor, the Emitter potential must be positive with respect to the

Base.

Then the transistor operates as a "single-pole single-throw" (SPST) solid state

switch. With a zero signal applied to the Base of the transistor it turns "OFF"

acting like an open switch and zero collector current flows. With a positive

signal applied to the Base of the transistor it turns "ON" acting like a closed

switch and maximum circuit current flows through the device.

An example of an NPN Transistor as a switch being used to operate a relay is

given below. With inductive loads such as relays or solenoids a flywheel diode

is placed across the load to dissipate the back EMF generated by the inductive

load when the transistor switches "OFF" and so protect the transistor from

damage. If the load is of a very high current or voltage nature, such as motors,

heaters etc., then the load current can be controlled via a suitable relay as

shown.

Circuit Basic NPN Transistor Switching

The circuit resembles that of the Common Emitter circuit we looked at in the



previous tutorials. The difference this time is that to operate the transistor as a

switch the transistor needs to be turned either fully "OFF" (cut-off) or fully

"ON" (saturated). An ideal transistor switch would have infinite circuit

resistance between the Collector and Emitter when turned "fully-OFF" resulting

in zero current flowing through it and zero resistance between the Collector and

Emitter when turned "fully-ON", resulting in maximum current flow. In practice

when the transistor is turned "OFF", small leakage currents flow through the

transistor and when fully "ON" the device has a low resistance value causing a

small saturation voltage (VCE) across it. Even though the transistor is not a

perfect switch, in both the cut-off and saturation regions the power dissipated by

the transistor is at its minimum.

In order for the Base current to flow, the Base input terminal must be made

more positive than the Emitter by increasing it above the 0.7 volts needed for a

silicon device. By varying this Base-Emitter voltage VBE, the Base current is

also altered and which in turn controls the amount of Collector current flowing

through the transistor as previously discussed. When maximum Collector

current flows the transistor is said to be saturated. The value of the Base

resistor determines how much input voltage is required and corresponding Base

current to switch the transistor fully "ON".



5.CD 4017 IC ACT AS BISTABLE MULTIVIBRATOR

Description

CD4017B is a 5-stage and Johnson counters having 10 and 8 decoded outputs,

respectively. Inputs include a CLOCK, a RESET, and a CLOCK INHIBIT

signal. Schmitt trigger action in the CLOCK input circuit provides pulse shaping

that allows unlimited clock input pulse rise and fall times.

These counters are advanced one count at the positive clock signal transition if

the CLOCK INHIBIT signal is low. Counter advancement via the clock line is

inhibited when the CLOCK INHIBIT signal is high. A high RESET signal

clears the counter to its zero count. Use of the Johnson counter configuration

permits high-speed operation, 2-input decode-gating and spike-free decoded

outputs. Anti-lock gating is provided, thus assuring proper counting sequence

Features

Fully static operation

Medium speed operation…10 MHz (typ.) at VDD = 10 V

Standardized, symmetrical output characteristics

100% tested for quiescent current at 20 V

5-V, 10-V, and 15-V parametric ratings

Meets all requirements of JEDEC Tentative Standard No. 13B, "Standard

Specifications for Description of ’B’ Series CMOS Devices"

Applications:

o Decade counter/decimal decode display (CD4017B)

o Binary counter/decoder



o Frequency division

o Counter control/timers

o Divide-by-N counting

o For further application information, see ICAN-6166 "COS/MOS MSI Counter

and Register Design and Applications"

6.ASK TRANSMITTER :

The TWS-434 and RWS-434 are extremely small, and are excellent for

applications requiring short-range RF remote control. The transmitter module is

only 1/3 the size of a standard postage stamp, and can easily be placed inside

small plastic enclosure.

TWS-434: The transmitter output is up to 8mW at 433.92MHz with a range of

approximately 400 foot (open area) outdoors. Indoors, the range is

approximately 200 foot, and will go through most walls.....

TWS-434A

The TWS-434 transmitter accepts both linear and digital inputs, can operate

from 1.5 to 12 Volts-DC, and makes building a miniature hand-held RF

transmitter very easy. The TWS434 is approximately the size of a standard

postage stamp.



TWS-434 Pin Diagram

7.ASK RECIVER: RWS-434: The receiver also operates at 433.92MHz, and

has a sensitivity of 3uV. The RWS-434 receiver operates from 4.5 to 5.5 volts-

DC, and has both linear and digital outputs.

RWS-434 Receiver

RWS-434 Pin Diagram

Note: For maximum range, the recommended antenna should be approximately

35cm long. To convert from centimetres to inches -- multiply by 0.3937. For


http://www.rentron.com/images/rws434med.jpg


35cm, the length in inches will be approximately 35cm x 0.3937 = 13.7795

inches long. We tested these modules using a 14", solid, 24 gauge hobby type

wire, and reached a range of over 400 foot. Your results may vary depending on

your surroundings.

AMPLITUDE-SHIFTKEYING

Amplitude-shift keying (ASK) is a form of modulation that

represents digital data as variations in the amplitude of a carrier wave.

The amplitude of an analog carrier signal varies in accordance with the bit

stream (modulating signal), keeping frequency and phase constant. The level of

amplitude can be used to represent binary logic 0s and 1s. We can think of a

carrier signal as an ON or OFF switch. In the modulated signal, logic 0 is

represented by the absence of a carrier, thus giving OFF/ON keying operation

and hence the name given.

Like AM, ASK is also linear and sensitive to atmospheric noise, distortions,

propagation conditions on different routes in PSTN, etc. Both ASK modulation

and demodulation processes are relatively inexpensive. The ASK technique is

also commonly used to transmit digital data over optical fiber. For LED

transmitters, binary 1 is represented by a short pulse of light and binary 0 by the

absence of light. Laser transmitters normally have a fixed "bias" current that

causes the device to emit a low light level. This low level represents binary 0,

while a higher-amplitude light wave represents binary 1.

Encoding

The simplest and most common form of ASK operates as a switch, using the

presence of a carrier wave to indicate a binary one and its absence to indicate a

binary zero. This type of modulation is called on-off keying, and is used


http://en.wikipedia.org/wiki/On-off_keying

http://en.wikipedia.org/wiki/Binary_numeral_system

http://en.wikipedia.org/wiki/Digital_data

http://en.wikipedia.org/wiki/PSTN

http://en.wikipedia.org/wiki/Amplitude_modulation

http://en.wikipedia.org/wiki/Binary_numeral_system

http://en.wikipedia.org/wiki/Phase_(waves)

http://en.wikipedia.org/wiki/Frequency

http://en.wikipedia.org/wiki/Signal_(electrical_engineering)

http://en.wikipedia.org/wiki/Carrier_wave

http://en.wikipedia.org/wiki/Amplitude

http://en.wikipedia.org/wiki/Data

http://en.wikipedia.org/wiki/Digital

http://en.wikipedia.org/wiki/Modulation


at radio frequencies to transmit RAYSUN code (referred to as continuous

wave operation),

More sophisticated encoding schemes have been developed which represent

data in groups using additional amplitude levels. For instance, a four-level

encoding scheme can represent two bits with each shift in amplitude; an eight-

level scheme can represent three bits; and so on. These forms of amplitude-shift

keying require a high signal-to-noise ratio for their recovery, as by their nature

much of the signal is transmitted at reduced power.

Here is a diagram showing the ideal model for a transmission system using an

ASK modulation:

It can be divided into three blocks. The first one represents the transmitter, the

second one is a linear model of the effects of the channel, the third one shows

the structure of the receiver. The following notation is used:

ht(f) is the carrier signal for the transmission

hc(f) is the impulse response of the channel

n(t) is the noise introduced by the channel

hr(f) is the filter at the receiver

L is the number of levels that are used for transmission

Ts is the time between the generation of two symbols


http://en.wikipedia.org/wiki/Signal-to-noise_ratio

http://en.wikipedia.org/wiki/Bit

http://en.wikipedia.org/wiki/Continuous_wave

http://en.wikipedia.org/wiki/Continuous_wave

http://en.wikipedia.org/w/index.php?title=RAYSUN_code&action=edit&redlink=1

http://en.wikipedia.org/wiki/Radio_frequency


Different symbols are represented with different voltages. If the maximum

allowed value for the voltage is A, then all the possible values are in the range

[−A, A] and they are given by:

the difference between one voltage and the other is:

Considering the picture, the symbols v[n] are generated randomly by

the source S, then the impulse generator creates impulses with an area

of v[n]. These impulses are sent to the filter ht to be sent through the

channel. In other words, for each symbol a different carrier wave is sent

with the relative amplitude.

Out of the transmitter, the signal s(t) can be expressed in the form:

In the receiver, after the filtering through hr (t) the signal is:

where we use the notation:

nr(t) = n(t) * hr(f)

g(t) = ht(t) * hc(f) * hr(t)

where * indicates the convolution between two

signals. After the A/D conversion the signal z[k] can

be expressed in the form:


http://en.wikipedia.org/wiki/Analog-to-digital_converter

http://en.wikipedia.org/wiki/Convolution


In this relationship, the second term represents the symbol to be extracted. The

others are unwanted: the first one is the effect of noise; the second one is due to

the intersymbol interference.

If the filters are chosen so that g(t) will satisfy the Nyquist ISI criterion, then

there will be no intersymbol interference and the value of the sum will be zero,

so:

z[k] = nr[k] + v[k]g[0]the transmission will be affected only by noise.

Probability of error. The probability density function of having an error of

a given size can be modeled by a Gaussian function; the mean value will be

the relative sent value, and its variance will be given by:

where ΦN(f) is the spectral density of the noise within the band and Hr (f) is

the continuous Fourier transform of the impulse response of the

filter hr (f).The probability of making an error is given by:

where, for example, is the conditional probability of making an error

given that a symbol v0 has been sent and is the probability of sending a

symbol v0.If the probability of sending any symbol is the same, then:

If we represent all the probability density functions on the same plot

against the possible value of the voltage to be transmitted, we get a

picture like this (the particular case of L = 4 is shown):


http://en.wikipedia.org/wiki/Conditional_probability

http://en.wikipedia.org/wiki/Probability_of_error

http://en.wikipedia.org/wiki/Continuous_Fourier_transform

http://en.wikipedia.org/wiki/Spectral_density

http://en.wikipedia.org/wiki/Variance

http://en.wikipedia.org/wiki/Normal_distribution

http://en.wikipedia.org/wiki/Probability_density_function

http://en.wikipedia.org/wiki/Nyquist_ISI_criterion

http://en.wikipedia.org/wiki/Intersymbol_interference


The probability of making an error after a single symbol has been sent is the

area of the Gaussian function falling under the functions for the other symbols.

It is shown in cyan just for just one of them. If we call P+ the area under one side

of the Gaussian, the sum of all the areas will be: 2LP + − 2P + . The total

probability of making an error can be expressed in the form:

We have now to calculate the value of P+. In order to do that, we can move the

origin of the reference wherever we want: the area below the function will not

change. We are in a situation like the one shown in the following picture:

it does not matter which Gaussian function we are considering, the area we want

to calculate will be the same. The value we are looking for will be given by the

following integral:


http://en.wikipedia.org/wiki/Probability_of_error

http://en.wikipedia.org/wiki/File:Ask_dia_calc_prob.png

http://en.wikipedia.org/wiki/File:Ask_dia_calc_prob_2.png


where erfc() is the complementary error function. Putting all these results

together, the probability to make an error is:

from this formula we can easily understand that the probability to make an error

decreases if the maximum amplitude of the transmitted signal or the

amplification of the system becomes greater; on the other hand, it increases if

the number of levels or the power of noise becomes greater.

This relationship is valid when there is no inter symbol interference, i.e. g(t) is

a Nyquist function.

8.POWER SUPPLY SECTION

Rectifier

A rectifier is an electrical device that converts alternating current (AC), which

periodically reverses direction, to direct current (DC), which is in only one

direction, a process known as rectification. Rectifiers have many uses including

as components of power supplies and as detectors of radio signals. Rectifiers

may be made of solid state diodes, vacuum tube diodes, mercury arc valves, and

other components.

.

The Full Wave Rectifier

In the previous Power Diodes tutorial we discussed ways of reducing the ripple

or voltage variations on a direct DC voltage by connecting capacitors across the

load resistance. While this method may be suitable for low power applications it

is unsuitable to applications which need a "steady and smooth" DC supply


http://www.electronics-tutorials.ws/diode/diode_5.html

http://en.wikipedia.org/wiki/Mercury_arc_valve

http://en.wikipedia.org/wiki/Vacuum_tube

http://en.wikipedia.org/wiki/Diode

http://en.wikipedia.org/wiki/Solid_state_(electronics)

http://en.wikipedia.org/wiki/Radio

http://en.wikipedia.org/wiki/Detector_(radio)

http://en.wikipedia.org/wiki/Power_supply

http://en.wikipedia.org/wiki/Direct_current

http://en.wikipedia.org/wiki/Alternating_current

http://en.wikipedia.org/wiki/Nyquist_ISI_criterion

http://en.wikipedia.org/wiki/Complementary_error_function


voltage. One method to improve on this is to use every half-cycle of the input

voltage instead of every other half-cycle. The circuit which allows us to do this

is called a Full Wave Rectifier.

Like the half wave circuit, a full wave rectifier circuit produces an output

voltage or current which is purely DC or has some specified DC component.

Full wave rectifiers have some fundamental advantages over their half wave

rectifier counterparts. The average (DC) output voltage is higher than for half

wave, the output of the full wave rectifier has much less ripple than that of the

half wave rectifier producing a smoother output waveform.

In a Full Wave Rectifier circuit two diodes are now used, one for each half of

the cycle. A transformer is used whose secondary winding is split equally into

two halves with a common centre tapped connection, (C). This configuration

results in each diode conducting in turn when its anode terminal is positive with

respect to the transformer centre point C producing an output during both half-

cycles, twice that for the half wave rectifier so it is 100% efficient as shown

below.

Full Wave Rectifier Circuit



The full wave rectifier circuit consists of two power diodes connected to a single

load resistance (RL) with each diode taking it in turn to supply current to the

load. When point A of the transformer is positive with respect to point C,

diode D1 conducts in the forward direction as indicated by the arrows. When

point B is positive (in the negative half of the cycle) with respect to point C,

diode D2 conducts in the forward direction and the current flowing through

resistor R is in the same direction for both half-cycles. As the output voltage

across the resistor R is the phasor sum of the two waveforms combined, this

type of full wave rectifier circuit is also known as a "bi-phase" circuit.

As the spaces between each half-wave developed by each diode is now being

filled in by the other diode the average DC output voltage across the load

resistor is now double that of the single half-wave rectifier circuit and is

about 0.637Vmax of the peak voltage, assuming no losses.



Where: VMAX is the maximum peak value in one half of the secondary winding

and VRMS is the rms value.

The peak voltage of the output waveform is the same as before for the half-wave

rectifier provided each half of the transformer windings have the same rms

voltage value. To obtain a different DC voltage output different transformer

ratios can be used. The main disadvantage of this type of full wave rectifier

circuit is that a larger transformer for a given power output is required with two

separate but identical secondary windings making this type of full wave

rectifying circuit costly compared to the "Full Wave Bridge Rectifier" circuit

equivalent.

The Full Wave Bridge Rectifier

Another type of circuit that produces the same output waveform as the full wave

rectifier circuit above is that of the Full Wave Bridge Rectifier. This type of

single phase rectifier uses four individual rectifying diodes connected in a

closed loop "bridge" configuration to produce the desired output. The main

advantage of this bridge circuit is that it does not require a special centre tapped

transformer, thereby reducing its size and cost. The single secondary winding is

connected to one side of the diode bridge network and the load to the other side

as shown below.

The Diode Bridge Rectifier



The four diodes labeled D1 to D4 are arranged in "series pairs" with only two

diodes conducting current during each half cycle. During the positive half cycle

of the supply, diodes D1 and D2 conduct in series while diodes D3 and D4 are

reverse biased and the current flows through the load as shown below.

The Positive Half-cycle



During the negative half cycle of the supply, diodes D3 and D4 conduct in

series, but diodes D1 and D2switch "OFF" as they are now reverse biased. The

current flowing through the load is the same direction as before.

The Negative Half-cycle

As the current flowing through the load is unidirectional, so the voltage

developed across the load is also unidirectional the same as for the previous two

diode full-wave rectifier, therefore the average DC voltage across the load

is 0.637Vmax. However in reality, during each half cycle the current flows

through two diodes instead of just one so the amplitude of the output voltage is

two voltage drops ( 2 x 0.7 = 1.4V ) less than the input VMAX amplitude. The



ripple frequency is now twice the supply frequency (e.g. 100Hz for a 50Hz

supply)

Typical Bridge Rectifier

Although we can use four individual power diodes to make a full wave bridge

rectifier, pre-made bridge rectifier components are available "off-the-shelf" in a

range of different voltage and current sizes that can be soldered directly into a

PCB circuit board or be connected by spade connectors. The image to the right

shows a typical single phase bridge rectifier with one corner cut off. This cut-off

corner indicates that the terminal nearest to the corner is the positive or +ve

output terminal or lead with the opposite (diagonal) lead being the negative or -

ve output lead. The other two connecting leads are for the input alternating

voltage from a transformer secondary winding.

The Smoothing Capacitor

We saw in the previous section that the single phase half-wave rectifier

produces an output wave every half cycle and that it was not practical to use this

type of circuit to produce a steady DC supply. The full-wave bridge rectifier

however, gives us a greater mean DC value (0.637 Vmax) with less

superimposed ripple while the output waveform is twice that of the frequency of

the input supply frequency. We can therefore increase its average DC output



level even higher by connecting a suitable smoothing capacitor across the output

of the bridge circuit as shown below.

Full-wave Rectifier with Smoothing Capacitor

The smoothing capacitor converts the full-wave rippled output of the rectifier

into a smooth DC output voltage. Generally for DC power supply circuits the

smoothing capacitor is an Aluminium Electrolytic type that has a capacitance

value of 100uF or more with repeated DC voltage pulses from the rectifier

charging up the capacitor to peak voltage. However, there are two important

parameters to consider when choosing a suitable smoothing capacitor and these

are its Working Voltage, which must be higher than the no-load output value of

the rectifier and its Capacitance Value, which determines the amount of ripple

that will appear superimposed on top of the DC voltage. Too low a value and

the capacitor has little effect but if the smoothing capacitor is large enough

(parallel capacitors can be used) and the load current is not too large, the output



voltage will be almost as smooth as pure DC. As a general rule of thumb, we are

looking to have a ripple voltage of less than 100mV peak to peak.

The maximum ripple voltage present for a Full Wave Rectifier circuit is not

only determined by the value of the smoothing capacitor but by the frequency

and load current, and is calculated as:

Bridge Rectifier Ripple Voltage

Where: I is the DC load current in amps, ƒ is the frequency of the ripple or twice

the input frequency in Hertz, and C is the capacitance in Farads.

The main advantages of a full-wave bridge rectifier is that it has a smaller AC

ripple value for a given load and a smaller reservoir or smoothing capacitor than

an equivalent half-wave rectifier. Therefore, the fundamental frequency of the

ripple voltage is twice that of the AC supply frequency (100Hz) where for the

half-wave rectifier it is exactly equal to the supply frequency (50Hz).

The amount of ripple voltage that is superimposed on top of the DC supply

voltage by the diodes can be virtually eliminated by adding a much improved π-

filter (pi-filter) to the output terminals of the bridge rectifier. This type of low-

pass filter consists of two smoothing capacitors, usually of the same value and a

choke or inductance across them to introduce a high impedance path to the

alternating ripple component. Another more practical and cheaper alternative is

to use a 3-terminal voltage regulator IC, such as a LM78xx for a positive output

voltage or the LM79xx for a negative output voltage which can reduce the ripple

by more than 70dB (Datasheet) while delivering a constant output current of

over 1 amp.



In the next tutorial about diodes, we will look at the Zener Diode which takes

advantage of its reverse breakdown voltage characteristic to produce a constant

and fixed output voltage across itself.

Linear Regulator

In electronics, a linear regulator is a voltage regulator based on an active

device (such as a bipolar junction transistor, field effect transistor or vacuum

tube) operating in its "linear region" (in contrast, a switching regulator is based

on a transistor forced to act as an on/off switch) or passive devices like zener

diodes operated in their breakdown region. The regulating device is made to act

like a variable resistor, continuously adjusting a voltage divider network to

maintain a constant output voltage. It is very inefficient compared to a switched-

mode power supply, since it sheds the difference voltage by dissipating heat.

Overview

The transistor (or other device) is used as one half of a potential divider to

control the output voltage, and a feedback circuit compares the output voltage to

a reference voltage in order to adjust the input to the transistor, thus keeping the

output voltage reasonably constant. This is inefficient: since the transistor is

acting like a resistor, it will waste electrical energy by converting it to heat. In

fact, the power loss due to heating in the transistor is the current times

the voltage dropped across the transistor. The same function can be performed

more efficiently by a switched-mode power supply (SMPS), but it is more

complex and the switching currents in it tend to produce electromagnetic

interference. A SMPS can easily provide more than 30A of current at voltages

as low as 3V, while for the same voltage and current, a linear regulator would be

very bulky and heavy.


http://en.wikipedia.org/wiki/Electromagnetic_interference

http://en.wikipedia.org/wiki/Electromagnetic_interference

http://en.wikipedia.org/wiki/Switched-mode_power_supply

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Current_(electricity)

http://en.wikipedia.org/wiki/Voltage_divider



http://en.wikipedia.org/wiki/Voltage_divider

http://en.wikipedia.org/wiki/Resistor

http://en.wikipedia.org/wiki/Zener_diode

http://en.wikipedia.org/wiki/Zener_diode




http://en.wikipedia.org/wiki/Field_effect_transistor

http://en.wikipedia.org/wiki/Bipolar_junction_transistor

http://en.wikipedia.org/wiki/Voltage_regulator

http://www.electronics-tutorials.ws/diode/diode_7.html


Linear regulators exist in two basic forms: series regulators and shunt

regulators.

Series regulators are the more common form. The series regulator works by

providing a path from the supply voltage to the load through a variable

resistance (the main transistor is in the "top half" of the voltage divider). The

power dissipated by the regulating device is equal to the power supply output

current times the voltage drop in the regulating device.

The shunt regulator works by providing a path from the supply voltage to

ground through a variable resistance (the main transistor is in the "bottom

half" of the voltage divider). The current through the shunt regulator is

diverted away from the load and flows uselessly to ground, making this form

even less efficient than the series regulator. It is, however, simpler,

sometimes consisting of just a voltage-reference diode, and is used in

very low-powered circuits where the wasted current is too small to be of

concern. This form is very common for voltage reference circuits.

All linear regulators require an input voltage at least some minimum amount

higher than the desired output voltage. That minimum amount is called

the dropout voltage. For example, a common regulator such as the 7805 has an

output voltage of 5V, but can only maintain this if the input voltage remains

above about 7V, before the output voltage begins sagging below the rated

output. Its dropout voltage is therefore 7V - 5V = 2V. When the supply voltage

is less than about 2V above the desired output voltage, as is the case in low-

voltage microprocessor power supplies, so-called low dropout

regulators (LDOs) must be used.

When one wants an output voltage higher than the available input voltage, no

linear regulator will work (not even an LDO). In this situation, a switching

regulator must be used




http://en.wikipedia.org/wiki/Low_dropout_regulator



http://en.wikipedia.org/wiki/Microprocessor

http://en.wikipedia.org/wiki/Dropout_voltage

http://en.wikipedia.org/wiki/Low-power_electronics



Using a linear regulator

Linear regulators can be constructed using discrete components but are usually

encountered in integrated circuit forms. The most common linear regulators are

three-terminal integrated circuits in the TO220 package. (The TO-220 package

is the same kind that many medium-power transistors commonly come in: three

legs in a straight line protruding from a black plastic molded case with a metal

black plate which has a hole for bolting to a heat sink).

Common solid-state series voltage regulators are the LM78xx (for positive

voltages) and LM79xx (for negative voltages), and common fixed voltages are 5

V (for transistor-transistor logic circuits) and 12 V (for communications circuits

and peripheral devices such as disk drives). In fixed voltage regulators the

reference pin is tied to ground, whereas in variable regulators the reference pin

is connected to the centre point of a fixed or variable voltage divider fed by the

regulator's output. A variable voltage divider (such as a potentiometer) allows

the user to adjust the regulated voltage.

FIXED REGULATORS

An assortment of 78xx series ICs

"Fixed" three-terminal linear regulators are commonly available to generate

fixed voltages of plus 3 V, and plus or minus 5 V, 6V, 9 V, 12 V, or 15 V when

the load is less than 1.5 amperes.


http://en.wikipedia.org/wiki/Ampere

http://en.wikipedia.org/wiki/78xx

http://en.wikipedia.org/wiki/Potentiometer

http://en.wikipedia.org/wiki/Ground_(electricity)

http://en.wikipedia.org/wiki/Disk_drive

http://en.wikipedia.org/wiki/Transistor-transistor_logic


http://en.wikipedia.org/wiki/TO220

http://en.wikipedia.org/wiki/Integrated_circuit

http://en.wikipedia.org/wiki/Integrated_circuit

http://en.wikipedia.org/wiki/File:7800_IC_regulatorsa.jpg

http://en.wikipedia.org/wiki/File:7800_IC_regulatorsa.jpg


The "78xx" series (7805, 7812, etc.) regulate positive voltages while the "79xx"

series (7905, 7912, etc.) regulate negative voltages. Often, the last two digits of

the device number are the output voltage; eg, a 7805 is a +5 V regulator, while a

7915 is a -15 V regulator. There are variants on the 78xx series ICs, such as 78L

and 78S, some of which can supply up to 1.5 Amps.

9.RELAY

A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the signal coming in from one circuit and re-transmitting it to another. Relays were used extensively in telephone exchanges and early computers to perform logical operations.

A type of relay that can handle the high power required to directly drive an electric motor is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protective relays

Basic design and operation

Simple electromechanical relay


http://en.wikipedia.org/wiki/Protective_relay

http://en.wikipedia.org/wiki/Moving_parts

http://en.wikipedia.org/wiki/Solid-state_relays

http://en.wikipedia.org/wiki/Contactor

http://en.wikipedia.org/wiki/Electromagnet

http://en.wikipedia.org/wiki/Switch

http://en.wikipedia.org/wiki/Electric

http://en.wikipedia.org/w/index.php?title=79xx&action=edit&redlink=1


http://en.wikipedia.org/wiki/File:Relay_Parts.jpg

http://en.wikipedia.org/wiki/File:Relay_Parts.jpg


Small relay as used in electronics

A simple electromagnetic relay consists of a coil of wire surrounding a soft iron core, an iron yoke which provides a low reluctance path for magnetic flux, a movable iron armature, and one or more sets of contacts (there are two in the relay pictured). The armature is hinged to the yoke and mechanically linked to one or more sets of moving contacts. It is held in place by a spring so that when the relay is de-energized there is an air gap in the magnetic circuit. In this condition, one of the two sets of contacts in the relay pictured is closed, and the other set is open. Other relays may have more or fewer sets of contacts depending on their function. The relay in the picture also has a wire connecting the armature to the yoke. This ensures continuity of the circuit between the moving contacts on the armature, and the circuit track on the printed circuit board (PCB) via the yoke, which is soldered to the PCB.

When an electric current is passed through the coil it generates a magnetic field that attracts the armature and the consequent movement of the movable contact(s) either makes or breaks (depending upon construction) a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage application this reduces


http://en.wikipedia.org/wiki/Magnetic_field

http://en.wikipedia.org/wiki/Magnetic_field

http://en.wikipedia.org/wiki/Electric_current

http://en.wikipedia.org/wiki/Printed_circuit_board

http://en.wikipedia.org/wiki/Printed_circuit_board

http://en.wikipedia.org/wiki/Spring_(device)

http://en.wikipedia.org/wiki/Armature_(electrical_engineering)

http://en.wikipedia.org/wiki/Magnetic_reluctance

http://en.wikipedia.org/wiki/Magnetic_core

http://en.wikipedia.org/wiki/Magnetic_core

http://en.wikipedia.org/wiki/Coil

http://en.wikipedia.org/wiki/File:Relay2.jpg

http://en.wikipedia.org/wiki/File:Relay2.jpg


Types

Latching relay noise; in a high voltage or current application it reduces arcing.

When the coil is energized with direct current, a diode is often placed across the coil to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to semiconductor circuit components. Some automotive relays include a diode inside the relay case. Alternatively, a contact protection network consisting of a capacitor and resistor in series (snubber circuit) may absorb the surge. If the coil is designed to be energized with alternating current (AC), a small copper "shading ring" can be crimped to the end of the solenoid, creating a small out-of-phase current which increases the minimum pull on the armature during the AC cycle.[1]

A solid-state relay uses a thyristor or other solid-state switching device, activated by the control signal, to switch the controlled load, instead of a solenoid. An optocoupler (a light-emitting diode (LED) coupled with a photo transistor) can be used to isolate control and controlled circuits.

Latching relay with permanent magnet

A latching relay has two relaxed states (bistable). These are also called "impulse", "keep", or "stay" relays. When the current is switched off, the relay remains in its last state. This is achieved with a solenoid operating a ratchet and cam mechanism, or by having two opposing coils with an over-center spring or permanent magnet to hold the armature and contacts in position while the coil is relaxed, or with a permanent core. In the ratchet and cam example, the first pulse to the coil turns the relay on and the second pulse turns it off. In the two coil example, a pulse to one coil turns the relay on and a pulse to the opposite coil turns the relay off. This type of relay has the advantage that one coil


http://en.wikipedia.org/wiki/Solenoid

http://en.wikipedia.org/wiki/Photo_transistor

http://en.wikipedia.org/wiki/Photo_transistor

http://en.wikipedia.org/wiki/Light-emitting_diode

http://en.wikipedia.org/wiki/Optocoupler

http://en.wikipedia.org/wiki/Thyristor

http://en.wikipedia.org/wiki/Relay#cite_note-0

http://en.wikipedia.org/wiki/Alternating_current

http://en.wikipedia.org/wiki/Snubber

http://en.wikipedia.org/wiki/Semiconductor

http://en.wikipedia.org/wiki/Voltage_spike


http://en.wikipedia.org/wiki/Direct_current

http://en.wikipedia.org/wiki/Arcing

http://en.wikipedia.org/wiki/File:Latching_relay_bistable_permanent_magnet.jpg

http://en.wikipedia.org/wiki/File:Latching_relay_bistable_permanent_magnet.jpg


consumes power only for an instant, while it is being switched, and the relay contacts retain this setting across a power outage. A permanent core latching relay requires a current pulse of opposite polarity to make it change state.



WORKING OF THE SYSTEM

WORKING OF THE COMPLETE SYSTEM

This is a new concept of security system in which PIR sensors commonly known as human body sensors are used to detect thermal radiations from human body.

Once the security system is initialised, this sensor senses the presence of any warm blooded animals. Thermal radiations that are continuously emitted from living animals detected by the sensor and corresponding voltage in the range of



mv are produced. This low voltage from sensor is amplified using a two stage amplifier. This amplified signal is compared with reference voltage using a comparator and the output of the comparator is used to trigger the bi-stable multivibrator and buzzer is initiated along with the light systems.

This signal is transmitted to the control station of the security control room for alerting the security officials.

COST ESTIMATION

PIR SENSOR D204B 1 350ASK MODULE 433 MHz 1 380IC HT 12E 1 42

HT12D 1 42CD4017 1 9LM 324 1 9LM7805 2 18LM7812 1 9

TRANSISTOR S8050 2 8S8550 1 4



SL100 1 9DIODE 1N4007 4 4

1N4148 2 2CAPACITOR 2200M/25V 1 12

100M/40V 2 8100M/25V 2 610M/25V 2 44.7M/25V 1 2104 4 4103 4 4

RESISTORS 10LED 6 6DIP SWITCH 8BIT 2 66SWITCH 230V/6A 2 46TRANSFORMER 0-12V 1A 1 85

0-18V 1A 1 105CONNECTOR 2PIN 4 12

4PIN 1 5RELAY 200E/12V 1 48

100E/12V 1 105IC BASE 18PIN 2 10

14PIN 1 416PIN 1 3

BUZZER 12V 2 48CABIN 8*6 1 550POWER CORD 240V/6A 1 80BATTERY 9VDC 1 25

SOLDERING LED 40-60 50g 68DOT PCB 6*4 2 88

TOTAL 2294



APPLICATIONS OF PIR SENSOR

Security systems Automatic lighting Systems Automatic Door Openers Common toilets, for lights & exhaust fans Common staircases For parking lights For garden lights For changing rooms in shops For corridors Motion-activated nightlight Alarm systems Robotics & Holiday animated props



Used VCRs and DVD players, to receive infrared light coming from a television remote.

PIR sensors are also used as motion detectors for most public doorways in grocery stores, hospitals, and libraries.

PIR sensors can also be used for military applications in the form of laser range finding night

ADVANTAGES

Small size makes it easy to conceal Compatible with all Parallax microcontrollers Very low power consumption 3.3V & 5V operation Able to detect infrared light from between several feet and several yards

away, depending on how the device is calibrated PIR sensors also do not need an external power source as they generate

electricity as they absorb infrared light Ability to be mass produced at low cost Imperviousness to interference from electromagnetic fields.



DISADVANTAGES

PIR sensors can also be expensive not only to purchase, but to install and calibrate as well.

PIR motion sensors are susceptible to false triggering due to environmental conditions or improper set-up

Loss of sensitivity when target and ambient temperature are close Normally cannot detect very slow-moving, small, or ectodermic

(cold-bodied, generally matching ambient temperature) targets.

Any obstacles in between the sensor & the target will limit the sensor’s coverage area & not give the desired result.

Any kind of moving object will trigger the sensor. They are not very accurate

CONCLUSION

We have used the easily available components from authorized distributors for this project to complete with full output within the allotted time period. The things we learned during the three years of course have been effectively made use of for the implementation of the project. We have collected materials and matter for this project from renowned electronic websites and authentic books. The cost of effective and basic components used in this circuit make this project worth its application. The circuit is reliable, easy to install everywhere. Thus we conclude by ensuring that our security system will guard all your valuable properties.


Sensor

Documents

mini project report

pir device

pir sensors

infrared source

construction of pir

human body sensor

infrared means

passive infrared radiation