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AC Live Line Detector

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A non-contact AC detector is an easy and safe AC live line tester device. It can detect the presence of an alternating current through a conductor without any electrical contact.


1. CD 4017 Ic
2. Led
3. Press Button.
4. Probe made of 5-20cm long, stiff insulated piece of wire.

How it works?

A probe or antenna is connected to pin 14 of the IC. The clock input of the 4017 IC has very high sensitivity, a small pulsating signal can provide an input clock for the counter. When the probe comes near to a current-carrying conductor an emf induced in the probe due to the magnetic field around the conductor. This emf gives the signal to the clock input.

As the LED has attached to one of the 10 output of the IC, the LED flashes once for 10 clock pulse inputs. Hence the LED flashes and indicates as it reaches near to a charged line including insulated wires, concealed wirings, etc.

The sensitivity of the circuit will vary with the length and conductivity of the probe.

As a safety measure to avoid electric shock always make sure the circuit has no direct contact with the live terminals. Always use the probe over an insulated surface or use an insulated probe. Ensure complete electrical isolation between the circuit and charged conductors to prevent any accidental contacts.

Keeping it away from the Live wire will eventually lower or breaks the capacitive coupling and thus the counter will stop and the LED will turn off.