Touch-Sensitive Switch (555)

Circuit Diagram

How to Build It

1. Place the NE555 timer chip on the board.
2. Connect pin 1 (GND) to ground and pin 8 (VCC) to +9V.
3. Connect pin 4 (RESET) directly to VCC.
4. Connect a 10K resistor from pin 2 (TRIGGER) to VCC — this normally keeps pin 2 HIGH.
5. Attach one bare wire to pin 2 and a second bare wire to ground — these are the two touch points.
6. Connect the LED (with current-limiting resistor) between pin 3 (OUTPUT) and ground.
7. Touch both wires simultaneously with your finger — the LED should turn on and stay on (your skin conducts just enough current to pull pin 2 low).

Bill of Materials