L84, Electromagnetic Field Detector

This circuit is sensitive to low frequency electromagnetic radiation and will detect for example hidden wiring or the field that encompasses a transformer. Pickup is by a radial type inductor, used as a probe which responds well to low frequency changing magnetic and electric fields. Ordinary headphones are used to for detection. The field that surrounds a transformer is heard as a 50 or 60Hz buzz.

Components-

• IC = UA741

• Resistors = 22K (2), 10K, 10R

• Variable resistor = 2.2M

• Capacitors = 100uf, 220uf, 100nf

• Inductor coil = 1mH (milihenry)a

• S1 = on/off Switch

• Battery 9volt