Hai i m karthika doing ECE 3rd year... i need to do some mini projects this year.. so i kindly request u to send me some ideas about lie detector and the circuit diagram for the same..

More Info About lie detector


some brief exolanation about lie detector


Lie detection is the practice of determining whether someone is lying. Activities of the body not easily controlled by the conscious mind are compared under different circumstances. Usually this involves asking the subject control questions where the answers are known to the examiner and comparing them to questions where the answers are not known. Critics claim that "lie detection" by use of polygraphy has no scientific validity because it is not a scientific procedure


refered by :
http://en.wikipediawiki/Lie_detection

some brief exolanation about lie detector


Lie detection is the practice of determining whether someone is lying. Activities of the body not easily controlled by the conscious mind are compared under different circumstances. Usually this involves asking the subject control questions where the answers are known to the examiner and comparing them to questions where the answers are not known. Critics claim that "lie detection" by use of polygraphy has no scientific validity because it is not a scientific procedure


refered by :
http://en.wikipediawiki/Lie_detection

PRESENTED BY:
HEMALATHA.T
SUDHA.S
SUSHMITHA.K

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ABSTRACT
 The detector circuit which we are going to do is for detecting a Lie.
 The lie detector circuit diagram consists of three transistors, a capacitor, two lights or LEDs, five resistors, and a variable resistor.
 The Lie Detector circuit is based on the fact that a person’s skin resistance changes when they sweat (sweating because they’re lying).
 Dry skin has a resistance of about 1 million ohms, whereas the resistance of moist skin is reduced by a factor of ten or more.
 We have also added an alarm circuit which will indicate when the person is telling lies so that it will help us as an alternate when there occurs a problem with the LED.
 This lie detector is a simple one and detects lie when the person sweats based on the fear when he lies so that the resistance level goes down when compared to the dry skin.
 We can also call this as a sweat detector.
 The Lie Detector has a number of other uses, detailed below, and it could perhaps more accurately be described as an 'Experiment Machine'.
Block Diagram
DESCRIPTION
VOLTAGE DIVIDER :
A voltage divider (also known as a potential divider) is a simple linear circuit that produces an output voltage that is a fraction of its input voltage.
A voltage divider referenced to ground can be created by connecting two electrical impedances in series
LOW PASS FILTER :
 A low-pass filter is a filter that passes low-frequency signals but attenuates (reduces the amplitude of) signals with frequencies higher than the cut off frequency.
 Capacitor can act as LPF and removes the 50Hz induced mains hum that is found on a person's body.
BUFFER AMPLIFIER :
 A voltage buffer amplifier is used to transfer a voltage from a first circuit, having a high output impedance level, to a second circuit with a low input impedance level.
 Unity gain voltage buffer is used.
VOLTAGE COMPARATOR :
A comparator is a device that compares two voltages or currents and switches its output to indicate which is larger.
Two transistors act as a voltage comparator. Depending upon voltage at the base of two transistor, the LEDs will come on.
POWER SUPPLY :
A 9v dc power supply is given using battery.
LED :
Depending upon the output from the voltage comparator either green or red LED will glow.
ALARM :
The alarm is connected parallel to red LED to produce alarm when the red LED glows to indicate the person is lying
CIRCUIT DIAGRAM
ALARM CIRCUIT
CIRCUIT DESCRIPTION
 The circuit diagram of the Lie Detector is shown above. It consists of three transistors (TR1 to TR3), a capacitor (C1), two lights or LEDs (L1 & L2), five resistors (R1 to R5), and a variable resistor (VR1).
 This circuit is based on the fact that a person's skin resistance changes when they sweat (sweating because they're lying).
 Dry skin has a resistance of about 1 million ohms, whereas the resistance of moist skin is reduced by a factor of ten or more.
 Resistors R1 and R2 form a voltage divider. They have resistances of 1 000 000 ohms (1 mega ohms) and, because their values are equal, the voltage at the upper probe wire is half the battery voltage (about 4.5 volts).
 A person holding the probe wires will change the voltage at the upper probe wire depending on their skin resistance.
 The skin resistance is in parallel with R2 and, because it is likely to be similar to or smaller than R2, the voltage at the probe wire will fall as skin resistance falls.
 Capacitor C1 functions as a smoothing capacitor and removes the 50Hz induced mains hum that is found on a person's body.
 TR1 and R3 form a buffer circuit (called an emitter-follower).
 The voltage at the emitter of TR1 follows the voltage at the probe wire and is now able to drive transistor TR2.
 Transistors TR1 and TR2 act as a voltage comparator.
 If the voltage at the base of TR2 is higher than at the base of TR3 then the green LED (L1) will come on.
 If the reverse is true then the red LED (L2) will light.
ALARM DESCRIPTION
 This small 3 transistors audio amplifier circuit will be suitable for small battery powered devices.
 The 3.3 ohm resistors connected to the emittters of PNP-NPN transistor couple, and the purpose of this resistors is to stabilize the transistor gain, so the temperature change won’t affect the performance much.
 Any PNP-NPN transistor couple with identical performance that capable of handling 100mA collector current should be suitable to replace the final transistors.
 The voltage swing of the output will be 2 Volt at maximum (at 9V DC supply), so the current at 8 ohm speaker will be 0.25A, and the maximum power would be the 2V*0.25A=0.5Watts.
WORKING
 To test the Lie Detector hold the probe wires.
 Adjust VR1 until the green LED is just on and the red LED is just off.
 This is the point at which the voltage at the base of TR2 is just greater than at the base of TR3.
 Now use moist fingers to hold the probes.
 This lowers the skin resistance and causes the voltage at the base of TR2 to fall.
 The voltage at the base of TR3 is now greater and the red LED comes on.
WORK SCHEDULE
 JAN 4th- Abstract Preparation.
 JAN 7th- Submitted Abstract for approval.
 JAN 17th-Necessary components were decided and block diagram was prepared.
 JAN 20th-Review.
 FEB 5th-Purchase of components.
 FEB 6th- Implementation of the circuit.
 FEB 9th- Circuit to be submitted for the approval.
 FEB 15th- Gathering information regarding our project.
 FEB 20th- Alterations in the circuit diagram.
 FEB 28th- Implementation of the Modified circuit diagram.
 MAR 3rd- Implementation of the circuit in PCB board.
 MAR 12th- Final verification of the output and our project model will be ready to be demonstrated.
 MAR 15th-Preparation of the complete paper.
 MAR 23rd- Presentation of the paper with demo for the approval.
 MAR 25th- Report preparation.
 MAR 30th- Report Submission.

PRESENTED BY:
RAHUL KHARE

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LIE DETECTOR
WHAT IS LIE DETECTER
 Lie detectors are the instruments that monitor a person’s reactions.
 Detect only the displacement in deceptive behavior.
CIRCUIT DIAGRAM
WORKING OF LIE DETECTORS
 RESPIRATORY RATE.
 BLOOD PRESSURE.
 GALVANIC SKIN RESISTANCE.
 ARM AND LEG MOVEMENTS.
PHYSIOLOGICAL RESPONSES
 POLYGRAPH EXAMINERS
(PSYCHOPHYSIOLOGIST)
FUNCTIONS
1. Setting up the polygraph and preparing the subject being tested.
2. Asking questions.
3. Profiling the test subject.
4. Analyzing and evaluating test data.
REQUIREMENTS
 Five years of investigative experience and associative degree.
 Students must attend and pass a ten week intensive course.
 Students must enter an internship program and conduct a minimum of 25 exams for actual cases.
ERRORS
 FALSE POSITIVE- the response of a truthful person is determined to be deceptive.
 FALSE NEGATIVE-the response of deceptive person is determined to be truthful.
COMMON COUNTERMEASURES
 The idea of counter measures is to cause a certain reactions that will skew the test’s result.
 Sedatives.
 Antiperspirant on finger tips.
 Tacks placed in shoes.
 Biting tongue ,lip or cheek.
WHO USES POLYGRAPHS?
 National security(central intelligence agency,FBI,national security agency,ext).
 Criminal investigation.
 Pre employment screening.
 Internal affairs investigations of law enforcements.
 Banks.
SHORTCOMMINGS AND COUNTERMEASURES
 PRESSURE ON THE SUBJECT.
 NO STANDARD PAPER FOR POLYGRAPH EXAMINERS.
 COUNTERMEASURES.
 POSSIBILITY OF HUMAN ERRORS IS ALWAYS THERE.
CONCLUSION
 Testing the conductivity of the human body.
 Testing the conductivity of objects.
 Determining whether a houseplant needs watering.
 Determining whether a cake is cooked.
 ON THE BASIS OF MY STUDIED I HAD CONCLUDED THAT THIS MACHINE IS 70% CORRECT FOR LIE DETECTING AND 100% FOR OTHER PURPOSES.

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Lie Detector Circuit Description:
The circuit diagram of the Lie Detector is shown above. It consists of three transistors (TR1 to TR3), a capacitor (C1), two lights or LEDs (L1 & L2), five resistors (R1 to R5), and a variable resistor (VR1). Suitable transistors to use are BC547, BC548 or BC549, or any other small NPN transistor.
The Lie Detector circuit works based on the fact that a person's skin resistance changes when they sweat (sweating because they're lying). Dry skin has a resistance of about 1 million ohms, whereas the resistance of moist skin is reduced by a factor of ten or more.
Resistors R1 and R2 form a voltage divider. They have resistances of 1 000 000 ohms (1 mega ohms) and, because their values are equal, the voltage at the upper probe wire is half the battery voltage (about 4.5 volts).
A person holding the Lie Detector probe wires will change the voltage at the upper probe wire depending on their skin resistance. The skin resistance is in parallel with R2 and, because it is likely to be similar to or smaller than R2, the voltage at the probe wire will fall as skin resistance falls.
Capacitor C1 functions as a smoothing capacitor and removes the 60Hz induced mains hum that is found on a person's body.
TR1 and R3 form a buffer circuit (called an emitter-follower). The voltage at the emitter of TR1 follows the voltage at the probe wire and is now able to drive transistor TR2.
Transistors TR1 and TR2 act as a voltage comparator. If the voltage at the base of TR2 is higher than at the base of TR3 then the green LED (L1) will come on. If the reverse is true then the red LED (L2) will light.
To test the Lie Detector hold the probe wires. Adjust VR1 until the green LED is just on and the red LED is just off. This is the point at which the voltage at the base of TR2 is just greater than at the base of TR3. Now use moist fingers to hold the probes. This lowers the skin resistance and causes the voltage at the base of TR2 to fall. The voltage at the base of TR3 is now greater and the red LED comes on.
How to Use the Lie Detector
The Lie Detector needs tuning before it can be used, and it needs tuning for every person that uses it as everyone has slightly different skin.
Touch the two probe wires against the palm of your (dry) hand, such that the metal ends are a couple of centimeters apart (the metal ends must not touch each other). Adjust the tuning control (VR1) until the red light (FALSE) just goes out. The Lie Detector is now tuned for your skin. If you lick your palm and touch the wires against it again, the red light should come on brightly.
You should now understand how to use the Lie Detector to detect a real lie. Touch the two probe wires against the palm of the subject's hand and adjust the tuning control as before until the red light just goes out. When the subject tells a lie, and begins to sweat, the red light will get brighter.
It must be emphasized that the Lie Detector won't detect every lie, as it is really only a sweat detector. It only detects lies that have consequences to being told, lies that cause the subject to sweat (with fear). Pretend or 'joke' lies won't have any effect.
The Lie Detector has a number of other uses, detailed below, and it could perhaps more accurately be described as an 'Experiment Machine'.
• Use lie detector to test the conductivity of the human body. Get a group of people to hold hands in a circle with the two probes of the Lie Detector as part of the circle. See how many bodies the current will flow through to make the red LED light.
• Testing the conductivity of objects. For example, metals, plastics, wood, hair, the lead of a pencil. If a material is conductive then touching the lie detector probe wires against it will make the red LED light.
• Determining whether a houseplant needs watering. Touch the lie detector probe wires against the soil. If the green LED stays on, the plant needs watering. If the red LED comes on, the soil is sufficiently moist.
• Determining whether a cake is cooked. Press the lie detector probe wires into the surface of the cake. If the red LED comes on then the cake is still moist and needs further cooking
Lie Detector Electronic Kit Specifications
• Lie Detector PCB dimensions 2" x 2" (5.08cm x 5.08cm)
• Power supply 9V battery (not included)
• Lie Detector electronic kit assembly is required
• Lie Detector kit is a great educational gift