1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Simple Lie Detector

Discussion in 'Electronic Projects' started by ElectroMaster, Jul 19, 2002.

Thread Status:
Not open for further replies.
  1. ElectroMaster

    ElectroMaster Administrator

    Joined:
    Jul 5, 2002
    Messages:
    2,057
    Likes:
    127
    Location:
    Broadbeach, AU
    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.

    [​IMG]
     
  2. Tom McCurdy

    Tom McCurdy New Member

    Joined:
    Dec 6, 2004
    Messages:
    38
    Likes:
    1
    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
     
    • Like Like x 1
  3. haerifar

    haerifar New Member

    Joined:
    Mar 28, 2004
    Messages:
    6
    Likes:
    0
    Location:
    Iran - Tehran
    nice post thanks
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. Shion Uzuki

    Shion Uzuki New Member

    Joined:
    Jun 2, 2003
    Messages:
    2
    Likes:
    0
    Location:
    University of Waterloo

    LOL cool
     
  6. Projek_01

    Projek_01 New Member

    Joined:
    Mar 11, 2005
    Messages:
    3
    Likes:
    0
    Nice. Thanks for the great ideal
     
  7. Projek_01

    Projek_01 New Member

    Joined:
    Mar 11, 2005
    Messages:
    3
    Likes:
    0
    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
     
  8. ibook

    ibook New Member

    Joined:
    Jun 1, 2005
    Messages:
    1
    Likes:
    0
    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. theinfamousbob

    theinfamousbob Member

    Joined:
    Mar 31, 2005
    Messages:
    546
    Likes:
    5
    Location:
    Cleveland, Ohio, USA
    I would use the meter out of one of those cheap battery testers that are about $4 US i think...
     
  10. yogpra

    yogpra New Member

    Joined:
    Jun 17, 2005
    Messages:
    1
    Likes:
    0
    Location:
    chennai,INDIA
    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. Roboticinfo

    Roboticinfo New Member

    Joined:
    Jan 15, 2005
    Messages:
    1,037
    Likes:
    0
    Location:
    USA, California
    reply

    Yep

    your skin resistance can go down because you are nervous or scared.

    So it is hard to tell
     
  12. subahu

    subahu New Member

    Joined:
    Jun 21, 2005
    Messages:
    2
    Likes:
    0
    what are the details of components?
     
  13. Roboticinfo

    Roboticinfo New Member

    Joined:
    Jan 15, 2005
    Messages:
    1,037
    Likes:
    0
    Location:
    USA, California
    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.
     
  14. lavanya389

    lavanya389 New Member

    Joined:
    Jul 25, 2005
    Messages:
    1
    Likes:
    0
    great one
     
  15. coolboy8505

    coolboy8505 New Member

    Joined:
    Jul 28, 2005
    Messages:
    5
    Likes:
    0
    That's really cool!
     
  16. coolboy8505

    coolboy8505 New Member

    Joined:
    Jul 28, 2005
    Messages:
    5
    Likes:
    0
    Sry, can anyone tell what is Electrodes?
     
  17. heathtech

    heathtech New Member

    Joined:
    Jun 6, 2005
    Messages:
    160
    Likes:
    0
    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.
     
  18. swap_too_fast

    swap_too_fast New Member

    Joined:
    Aug 9, 2005
    Messages:
    1
    Likes:
    0
    Location:
    nasik
    plz, tell me taht how I can know that someone tells me lie, means which is the indicator in the circuit.
     
  19. Someone Electro

    Someone Electro New Member

    Joined:
    Sep 10, 2003
    Messages:
    2,579
    Likes:
    2
    Location:
    A boring village in Europe (slovene)
    M1 is the indicator
     
  20. spy_genius

    spy_genius New Member

    Joined:
    Nov 7, 2005
    Messages:
    3
    Likes:
    0
    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.
     
  21. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,294
    Likes:
    647
    Location:
    Derbyshire, UK
    ONLINE
    Any small signal NPN should be fine, the higher gain the better.
     
Thread Status:
Not open for further replies.

Share This Page