During the summer I have many times to build gadgets, and when I found this easy circuit on the internet I' ve decided to make my own and to show you how to build a lie detector. First of all I am 15 now and now learn english in the school so sorry for my bad english. When you put your fingers on the touchpads you activate the circuit and you will hear a static noise. If you lie your fingers will get moist and the speaker will change its noise.
Step 1: Tools and Materials
*Materials: 2 AA Batteries
-9V battery clip (if you have a battery box like me)
-A small cardboard box
-A 8R speaker
-2x100k and 1x1k resister
-1 BC557 transistor and 1 BC547 transistor
-2 pieces of 1.5x1.5 inch aluminium foil
*Tools: Soldering Iron, Glue Gun, Needle
Step 2: Making the Circuit
I've made my circuit with an other speaker, but it worked fine. You need to solder two wires to the touchpads, because those will come out from the box. Be careful with the transistors, one of them is NPN and the another is PNP.
Step 3: Building the Case
1. With a glue gun we need to glue everything inside the cardboard box. On the bottom I put the 9V battery clip, because my battery box can connect to it, on the top is the speaker. With a needle you need to make two holes for the wires of the touchpads and ten or more holes for the speaker. The electronics are just simply soldered together, not on a PCB board. You can make another design. At the end you need to make the touchpads, which connects to the two wires.
Step 4: Testing
Put your fingers on the touchpads, and lie for a question. If you lie you will hear a static noise.
Now make your own lie detector and try it on a freind!
This is an easy project for school, or just for fun. I hpe you like it!
LillianG made it!