This is the FIRST Lie Detector project on Instructables.
Watch the video and then build it...
Step 1: Parts You Will Need...
I picked up all of the components at Radio Shack except for a few I list at the end.
1. Project Enclosure
2. 4.7K Resistor
3. 82K Resistor
4. 0.01uF Capacitor
5. 2N3904 Transistor
6. 2N3906 Transistor
7. 2-AA Battery holder
8. Small circuit board
Spare PC speaker, velcro, aluminum foil, wire and AA batteries in my extra parts bin.
Step 2: Basic Tools...
You will need a soldering iron/station, solder, screwdriver, hot glue, small drill bit and wire strippers.
Step 3: Build the Circuit...
Following the schematic shown here, build the circuit. Take your time and make good solder joints.
Step 4: Make the Finger Pads...
Install everything in the project enclosure leaving just the Finger Pad leads exposed through drilled holes. I also drilled holes in the box so you can hear the speaker.
I got the finger pad design from this article.
Using a strip of Velcro (soft side), cut a piece of aluminum foil the size of the veclro. Make sure the velcro is long enough to go around a big, fat finger. Some liars are chubby. Remove the sticky side of the velcro and attach the aluminum foil with one of the Finger Pad leads under the aluminum. Then use a smaller piece of the other part of the velcro (the 'hook' side) and attach it to the end so the whole pad can be wrapped and secured.
Step 5: Test It Out...
This works on the galvanic skin response. When you lie, your skin becomes moist. While this does work, it's not as accurate as a true Polygraph machine. Hope you enjoyed this Instructable and for another really good DIY Lie Detector, check out Jason Bradbury's!