Development of a Low Cost Microcontroller Based Under and Over Voltage Protection Device

This paper presents the design and construction of a low cost under and over voltage protective device, which was fabricated using a microcontroller, transistor, IC and other discrete components. A microcontroller PIC16F877 is at the heart of the device which performs the major control of the device. The device is simple and of low cost. It can withstand loads up to 2KVA and the required set voltage range for the device to allow supply to the connected load at the output varies from 200-240 Volts. It can be used to protect loads such as refrigerator, T.V., VCR/DVD players etc. from undesirable over and under voltages, as well as surges caused due to sudden failure/resumption of mains power supply. This device can be used directly as a standalone equipment between the mains supply and the load, or it may be inserted between an existing automatic/manual stabilizer and the load. The over/under voltage cut-off with time delay provides over/under-voltage protection, and protection against transients.