How to Build a Lie Detector

Are you curious to see if your loved one is lying to you? Are you trying to make a cool gadget for your next party? Or are you working on a science project? This simple lie detector can be made at home, using fairly simple electronic tools. If you are a child, please have an adult work with you.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• 33K 1/4W Resistor
• 5k Pot
• 1.5K 1/4W Resistor
• 1uF 16V Electrolytic Capacitor
• 2n3565 NPN Transistor
• 0-1 mA Analog Meter
• Electrodes
• Wire
• Casing

Electrodes

1. Find something suitable to use for the electrodes. You can use alligator clips, but that could end up being quite harmful to the person you are testing. You can use those electrode pads that are found in hospital equipment, but you could also just use wire and tape.

2. Assemble the parts according to the instructions in the schematic design -- in the picture above. Do NOT hook anyone up to this until you have finished the entire assembly process.

3. Hook the electrodes up to the back of the test subject's hand. Space the electrodes about an inch apart. Set the meter to where it defaults at zero. If the meter changes, the subject is lying.

4. Testing resistance: This detector tests for a decrease in skin resistance. When you lie, your skin loses some of its ability to resist pressure. This system will test that resistance and alert you when a lie is being told. Beware -- it is not as sophisticated as the machines that professional testers use.

Tips & Warnings

• Remember -- this is not a professional-grade lie detector test.
• Electricity can be dangerous! Follow the directions and schematic precisely.

Resources

• Information about the Electronics Involved