Wednesday, August 27, 2008

Neutral Tampering

This tampering is done by disconnecting the neutral wire in the domestic electricity meter. The circuit designed for the detection of neutral tampering is shown above.

The component used for the neutral tampering detection circuit is an Optocoupler connected in parallel to the Voltage coil.

The circuit works as follows. As long as the neutral and the phase are connected to the voltage coil, the parallely connected Optocoupler LED produces a high output therby biasing the base of the photo transistor which produces an output at the emitter. This output is continuously monitored by the microcontroller.

When the neutral wire from the electricity meter is disconnected, the power supply to the LED is also disconnected and hence it does not glow. As soon as the LED fails to glow, the photodiode is unbiased and its output drops to low level or logic “0” signal and it sent to the micro controller. The microcontroller senses this change in optocoupler output and thus intimates the GSM modem to send a message to the Electricity board regarding the Neutral tampering.

The micro controller is programmed using embedded C so as to intimate and transfer signals according to the signals received ( either “1” or “0”). When micro controller receives the signals, it transfers it to the LCD and the GSM modem. So an information about the tampering that has occurred is displayed in the LCD, as well as sent to the electricity board through the GSM modem.

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