This is a fun device that you can use to detect AC currents flowing in a wire, for example to find hidden wires in your walls. It’s a fun device for experimenting with detecting electromagnetic waves, but do not use it as a safety device.

It’s a simple circuit that only requires a few BC547 transistors for detection and a buzzer and/or LED for indicating detection.

What You’ll Need

• 3x BC547 Transistor
• LED
• Buzzer (Active)
• 220 Ω Resistor
• Piece of solid wire
• 9V Battery
• Battery connector
• Perfboard