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Ideas

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Duckvader

New Member
Galvanic Skin Response

Skin resistance to detect a lie uses simple circuits like resistors to light up LEDs. If it is juz measuring resistance wouldnt it be simpleir juz using a ohm meter and measure it direcly.

If I want to display the value on a computer screen, what can use advice me on the circuit needed.

Wat program should I write???

We can measure the Voltage or Current difference.

I'm hoping to gather some values for comparison.

Do I still need to uses ADC????

Pluging some electrode to the fingers juz like tat and connect to a com running under some program seems scary.

Pls elobarate some ideas to me to solve tis problem.
 

HiTech

Well-Known Member
Biofeedback Monitor for the PC
**broken link removed**
This circuit uses an LM555 to form a biofeedback monitor that connects to a personal computer. Probe A and B are simply two foil strips glued to the cover of the case the parts are mounted in. This circuit measures the galvanic skin response (GSR) which indicates tension. As you relax, your skin resistance increases. The LM555 is configured as a pulse generator. The width of the pulse proportional to the product of C1, R1, and the skin resistance between probes A and B. PL1 is the printer port of a PC. Pin 16 , the INIT line, connects to the trigger input of the LM555. Sending a short pulse INIT pulse causes the output (pin 3) to go high, Pin 3 goes low at the end of the pulse. This time, from high to low, is an indicator of the GSR. Pin 20 is ground. Software must be written (or see Radio-Electronics Oct, 1988 page95) to operate the unit. To run the monitor, place your index finger on one probe and your second finger on the second probe. Do not move your fingers or change their pressure. The unit may also operate as a rudimentary lie-detector.
 

billymas

New Member
sory,its me (duckvader),i use my frens id to start this post,
so now we hv the circuit,
& whats the most suitable software to program it in order to run it?
 

philba

New Member
I thought the 555 wasn't spec'd to run at 3V. I did a quick check and the NE555 and LM555 have a min voltage of 4.5. However, the LMC555 (CMOS version from nat semi) looks to go down to 1.5V. so, best use a CMOS 555.

and billy, please use English, not IMglish.
 

penoy_balut

New Member
based on HiTech's circuit, put pin 2 to low to trigger the timer IC, then start a VB timer then poll pin 3 until its low, turn off VB timer, time is proportional to skin resistance
 

philba

New Member
billy, in case you haven't figured out, no one is going to do your school assignment for you. If make a good faith effort to design the code you will probably get help.
 
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