PROJECT TITILE: POLARITY GUARD FOR AC/DC ADAPTOR ABSTRACT The research aims at the designing and implementation of an automatic voltage regulator (AVR) with high precision and hysteresis. The AC power supplied by KPLC (Kenya Power) subjected to variation from time to time. Moreover, in rural areas supplied voltage remains lower than specified. This causes a considerable threat to the sophisticated electronic device to the computer, refrigerator, television etc. So, ensuring the input voltage to remain in a tolerable pre-specified limit has become a necessity in rural as well as some urban areas. Current system available locally lack precision and suffers the problem oscillating between two output voltage and hence creating surge at the output which can damage valuable electronics. This project handles both shortcomings and introduces the tolerable range of 12 1 voltage output. MERIT The circuit is simple but useful for wall AC/DC adaptors where it is important to reduce ripples and noise, and improve transient response of the adaptors. It can also be used in a wide range of switching and analogue power supplies. The circuit has been developed for 26V and 19V wall adaptors, but by replacing some components, it can be used for other wall adaptors with output voltage starting from 5V. When input polarity is fixed, the bridge can be replaced with simple diodes depending on requirement.