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!