This circuit measures temperature in Celsius scale and displays it on an alphanumeric LCD screen
When temperature rise to 40 C an alarm is activated and at the same time a relay is also activated which
drives a fan to keep the temperature at a level. Another feature of this circuit is that you can use the keys “1,2,3,4” of a Philips TV IR remote to turn on or off three relays, The key ‘4’ is used to turn on or off the over temperature alarm.
IR Digital Thermostat for FAN – [Link]