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Transcript of Sensor
MINI PROJECT REPORT 2011 PIR SENSOR BASED SECURITY SYSTEM
INTRODUCTION
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MINI PROJECT REPORT 2011 PIR SENSOR BASED SECURITY SYSTEM
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.
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BLOCK DIAGRAM
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MINI PROJECT REPORT 2011 PIR SENSOR BASED SECURITY SYSTEM
BLOCK DIAGRAM
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COMPARATORCOMPARATOR
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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
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MINI PROJECT REPORT 2011 PIR SENSOR BASED SECURITY SYSTEM
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
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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.
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CIRCUIT DIAGRAM
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CIRCUIT DESCRIPTION
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MINI PROJECT REPORT 2011 PIR SENSOR BASED SECURITY SYSTEM
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
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MINI PROJECT REPORT 2011 PIR SENSOR BASED SECURITY SYSTEM
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 -
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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
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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
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— 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.
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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-
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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).
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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.
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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:
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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:
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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.
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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
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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.
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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:
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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.
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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.
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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
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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".
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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
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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.
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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
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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
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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
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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:
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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):
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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:
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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
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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
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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.
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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
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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
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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
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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
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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
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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.
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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.
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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
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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.
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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
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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
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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
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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.
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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
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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
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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
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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
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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.
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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.
DEPT. OF ELECTRONICS & INSTRUMENTATION Page 62