You can control almost anything you want based on temperature with this. If you connect a fan through the relay, you can have it turn on when it gets warm in the room, and turn itself off when it cools down to your set temperature! You can adjust both the high temperature (that it switches on at) and the low temperature (at which it will finally turn back off). It can also be reversed, so that you can have a heater attached instead of a fan (as long as it's no more than 5 Amps through the relay, but you can wire it to the heater's control dial, instead of the hot powersupply wire, so that there probably isn't as much current, but always measure first with your multimeter to be sure) so that it will stay on warming up the room until the high temperature is reached, then stay off until it gets to the low temperature!

Specifications

Power supply : PS1205R 12 VDC./ max 250 mA.

Max load for the relay: 500 Watts.

Sensor temperature range: -20 to +100 Celsius

Display: 3.5 digits

There is also LED indication for power on/off and relay on/off.

This is a fully assembled and tested module.