This is a very easy useful project of a non contact AC voltage detector circuit. The circuit will blink an LED and make beep beep sound when it detects any AC field. The circuit can be used to check AC voltage in wires, switches, plugs, wall sockets, electronic devices etc. without making a direct contact.
It will also show the phase and neutral wire from the two AC wires by making beep and blink LED only on phase wire and being in off state on neutral wire.

The circuit is using a 555 timer IC, a 2N3819 FET (Field effect transistor) with some resistors and capacitors. The 2N3819 transistor is working as AC field detector and the beeper circuit is built around the 555 timer IC.

The circuit can be operated from 6 to 12 volt DC. If you are operating the circuit with lower voltage then change the LED current limiting resistor according to the operating voltage to brightly blink the LED. On six volt you can use a 270 ohms resistor, On 9 volts use 320 ohms and on 12 volt use 470 ohms. The antenna can be a 2 to 4 inch wire, do not remove the insulation from the wire and wound a good plastic tape on the antenna from tip to bottom so it will not come in contact with the AC directly.

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Non Contact AC Voltage Detector Circuit Diagram