ABSTRACT
This project design and construction of over and under voltage protection circuit device (180V – 240V) is aimed at designing and construction of a device that can operate within a specified voltage range thereby helping to prevent the risk of voltage surge and burnouts. The device consists of a power supply unit which supplies power to all components within the circuit, two comparator units for detecting various levels of supply voltage (comparator unit 1 helps in monitoring the limit of the supply voltage i.e. 240V while comparator unit two helps in monitoring the lower limit of the supply voltage i.e. 180V), a transistor operating as a switch to trigger the final unit which is the relay (depending on the voltage level) that is directly connected to the load (e.g. refrigerator).