Electrical leakage can cause lethal shocks. But such an unfortunate situation can be avoided with this shock warning system. It uses minimal number of components and does not need any separate power supply.
Shock warning system circuit
The circuit continuously monitors the leakage from an electronics gadget by sensing the potential in its body. When there is leakage from the body, the potential exists across the neutral end and the body of the gadget, which charges capacitor C1 through diode D1 and resistor R1. When the voltage across capacitor C1 exceeds the break-down potential of DIAC1 (DB3), it starts conducting and the capacitor discharges through the buzzer as well as LED1 quickly. This discharge energy makes LED1 flash and piezobuzzer sound momentarily. As long as there is leakage from the body of the gadget, there is intermittent warning from the buzzer as well as from the LED.
Construction & testing
Assemble the circuit on a general purpose PCB and connect it to the mains operated gadget. This circuit can be used for washing machines, refrigerators and other similar mains operated devices.
The articl ewas first published in January 2009 and has recently been updated.