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Simple Lie Detector

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Thread starter #1
Here's a simple lie detector that can be built in a few minutes, but can be incredibly useful when you want to know if someone is really telling you the truth. It is not as sophisticated as the ones the professionals use, but it works. It works by measuring skin resistance, which goes down when you lie.

 
#2
Details of Parts

Here are the details of the specific parts you will need


Part Total Qty. Description Substitutions
  • R1 1 33K 1/4W Resistor
    R2 1 5K Pot
    R3 1 1.5K 1/4W Resistor
    C1 1 1uF 16V Electrolytic Capacitor
    Q1 1 2N3565 NPN Transistor
    M1 1 0-1 mA Analog Meter
    MISC 1 Case, Wire, Electrodes (See Nots)

Notes
1. The electrodes can be alligator clips (although they can be painful), electrode pads (like the type they use in the hospital), or just wires and tape.

2. To use the circuit, attach the electrodes to the back of the subjects hand, about 1 inch apart. Then, adjust the meter for a reading of 0. Ask the questions. You know the subject is lying when the meter changes.




http://www.aaroncake.net/circuits/lie.htm
 
#6
Hi, I live in a small city and I cant seem to find the correct transistor, do you think there could be any subsitutions? Thanks

Do you think any of these would work?
2N1711
2N3417
2N3439
2N3440
2N3440
2N3771
2N4124
2N4126
2N4400
2N4401
Thanks again
 

ibook

New Member
#7
the meter, does anyone know where to get one of the cheap. I went to local electronics store and the cheapest I saw was 5 bucks. What meter did you use OP. or could you cut me a link to some cheap ones.
 
#9
hi it was gr8
but ..is there any chance that our skin resistance does not go down when we lie..if so the lie detector would say a lie...
thanks
bye
 
#11
ElectroMaster said:
Here's a simple lie detector that can be built in a few minutes, but can be incredibly useful when you want to know if someone is really telling you the truth. It is not as sophisticated as the ones the professionals use, but it works. It works by measuring skin resistance, which goes down when you lie.

what are the details of components?
 
#12
reply

What are you talking about?

All the information is on this page and on the schematic except the transistor.

But it is documented on this page.
 
#16
Electrode:
A solid electric conductor through which an electric current enters or leaves an electrolytic cell or other medium.
A collector or emitter of electric charge or of electric-charge carriers, as in a semiconducting device.
 
#19
The 2N3565 NPN Transistor is not available in my place.Can i use a substitution for that.Someone please reply as to where i can get that transistor.I live in india in a place called Mangalore.I liked the idea of this project and decided to do it.But now the transistor and the analog meter in unavailable.So pls tell me where can i get these two parts.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
#20
spy_genius said:
The 2N3565 NPN Transistor is not available in my place.Can i use a substitution for that.Someone please reply as to where i can get that transistor.I live in india in a place called Mangalore.I liked the idea of this project and decided to do it.But now the transistor and the analog meter in unavailable.So pls tell me where can i get these two parts.
Any small signal NPN should be fine, the higher gain the better.
 
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