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Kaustubh Katdare
Kaustubh Katdare • Jan 18, 2009

Electronics Mini Project Idea: Simple Electronic Lie Detector

I came across a nice project idea on electro-tech-online. Its about simple electronic lie detector.

It works on following concept:

When you lie, your skin's resistance goes down. The circuit should measure the skin resistance and turn on a light when the resistance is goes below some set value.

What say? Anyone?
silverscorpion • Jan 18, 2009
I have a subject medical electronics in this sem and I have to do a mini project in that subject. I can very well take up this project. I was thinking more on bio potential measurement, like designing amplifier for ECG,EEG etc. Well, I was thinking about skin resistance too.
Problem is, these ideas are conceptually very simple, but are rather difficult to implement. Because, I dont think the change in resistance will be very much greater than some micro ohms and for such a small change to be captured and amplified, we need devices which are very very sensitive. There lies the problem.
Anyhow, I've to do a project, and I my as well do this. I'll post more after a quick research..
Kaustubh Katdare
Kaustubh Katdare • Jan 18, 2009
Engineers solve complicated problems, scorpion 😉 . I'm sure you'll do this project. Keep us posted with your proceedings, circuit diagrams, problems you faced and how you cracked them. 😀

All the best!
silverscorpion • Jan 19, 2009
It seems I was wrong.. The human skin in it's dry state has a huge resistance and when a person lies, due to fear, he sweats. the resistance of moist skin is much lower than that of the dry skin and the amount of lowering is a staggering five to ten percent, which is in the order of kilo ohms. There should be no problem in detecting the lowering of resistance.

Thinking about that, I found one small problem though, and it's not technical. This project actualy is a sweat detector and if a person lies without sweating, it cant be detected. So, the person on whom this device is tested must be really in fear. It wont work for "joke" lies. Now tell me how I can present the project to my professor..
aforadi • Jan 24, 2009
sumith123 • Jun 19, 2010
but its not a simple problem
because resistance value differ from each other body
so i think no default value can set on it

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