The main objective of this paper is to display the temperature and when it goes beyond certain limit then control it to bring it back into desired level and reduce waste of energy. And also to assist people who are disabled and are unable to control the speed of fan. It may also be used for monitoring changes in environment. In near future, it can also be used in different industries and electronic devices. Another objective is to study and build an automatic system using microcontroller and its interfacing with other device. Nowadays Arduino becomes more popular because of its many advantages like simple programming and compact in size and it supports many device.