MICROCONTROLLERS with their inherent advantages are being increasingly used in the industry. With growing shortage and escalating cost of Electrical Energy, accurate monitoring of Air Conditioner's parameters has become necessary. 'A/C CONTROLLER is most useful for controlling A/Cs. These instrument is able to maintain Room Temperature with an accuracy of 0.1 Degree Celsius by automatic measurement of Room temperature and accordingly controlling A/C ON/OFF.It also protects Costly Air conditioner from Unhealthy condition's such as over load/under load etc. by automatically shutting down to it