This is a very simple circuit that can be used to sense electromagnetic radiations. The circuit can even detect hidden wrings. A 1mH inductor is used for sensing the electric field. The electric field will induce a small voltage in the sensor inductor and this induced voltage is amplified by the opamp.The headphone connect at the output of the opamp will give an audio indication of the electric field. For example, the electric field around a mains transformer can be heard as a 50 Hz hum. The POT R4 can be used to adjust the gain of the amplifier. By keeping the sensor inductor near to a telephone line, you can even hear the telephone conversations.
Circuit diagram with Parts list.
- Assemble the circuit on a general purpose PCB.
- The circuit can be powered from a 9V PP3 battery.
- It is better to have a radial type inductor for L1.
- The POT R4 can be used to adjust the gain.
- The switch S1 can be a slide type ON/OFF switch.
- The IC1 must be mounted on a holder.
- All electrolytic capacitors must be rated at least 15V.