Simple temp control for home use

My friend was complaining that his entertainment system ( which as the amplifier, video game console, DVD player, cable box etc) was getting too hot. He wanted a fan that will come on only when the temp raises to a certain point and then auto shut off so he didn't have to deal with the noise.


Attached is a simple circuit.

It uses the following

1) 5V relay (I used a coto)
2) LDO to step from 12V to 5V (since I used a 12V fan and the temp sensor chip can only handle upto 5.5V) I used Micrel MIC2920-5.0 LDO.
3) Maxim MAX6509 temp sensor with hysteresis
4) Some capacitors for bypassing
5) A 12V DC ultra quiet fan (junk store sells them for $3)


You have to adjust the Hysteresis resistor to the temp that you want..

It works great.. Let me know if you have any questions..

BTW the reason I used a mechanical relay instead of a FET is because in order to turn on the fan, it needs a surge current. If you slowly apply the 12V, the fan will not turn on. In order to quickly turn on a FET with the output of this device I will have to use another FET driver and it makes things unnecessarily complicated..

newb said:

BTW the reason I used a mechanical relay instead of a FET is because in order to turn on the fan, it needs a surge current. If you slowly apply the 12V, the fan will not turn on. In order to quickly turn on a FET with the output of this device I will have to use another FET driver and it makes things unnecessarily complicated..

Click to expand...

You could have used a logic level FET, no need for a driver.

BTW, you should have a free-wheeling diode across the relay coil.

@Barry
Good points. Didn't think about the logic FETs
I forgot about the diode.
Thanks...

BTW,you should have a tank capacitor nearby the relay pin 1.

You can see this simple solutions:

**broken link removed**




**broken link removed**




https://www.irv2.com/forums/f53/cooling-fan-for-entertainment-cabinet-38446.html