Circuit for prepaid energy meter

The above designed circuit represents a prepaid energy meter. This circuit uses the Atmel IC 8052 i.e. AT89S52 an 8-bit microcontroller IC.AT89S52 is a low voltage, high performance CMOS 8-bit microcontroller with 8K bytes of In-System programmable (ISP) flash memory and a three level program memory lock. It has operating range from 4.0V to 5.5V. AT89S52 is also equipped within by a 256X8-bit internal RAM and three 16-bit counters. Also, the IC ULN2003 used is a high voltage, high current Darlington array containing seven open collector Darlington pairs with common emitters. Each channel is rated at 500 mA and can withstand peak currents of 600 mA. In it suppression diodes are integrated for inductive load driving and the inputs are pinned opposite the outputs to simplify board layout. The IC used AT24C02 is a two-wire serial EEPROM. It provides 2048 bits of electrically erasable and programmable read only memory organized as 256 words of 8 bits each. It is very useful in applications where low-power and low-voltage operation are essential.