How to Make a Simple Temperature Control Fan Speed

Intro: How to Make a Simple Temperature Control Fan Speed

Step 1: Electronic Parts You Need

1 x 10K thermistor

1x IRF540n or n channel MOSFET

1 x 50 kilo-ohms potentiometer

1 x 2.2 uf 16 volts at least capacitor

Step 2: Connect All Parts As the Image Above

This circuit uses a thermistor as a sensor, the thermistor resistance decrease when a temperature increase.

When the temperature increases the thermistor resistance decrease until the voltage set point that adjusts by potentiometer higher than Vgs threshold, MOSFET change to ON state and make a 12 volts fan start and rotating speed faster when a temperature hotter.

The capacitor that parallels with a thermistor help fan starts instantly at lowest speed when power on, The 12 volts DC fan make noise and not rotating without the capacitor(maybe a cheap Chinese power supply cause it).

I set the threshold point at 25 C, The fan start at lowest speed @ 25 C and rotating fastest @ around 38 C (I touch it and wait few munites to see the result)

Enjoy DIY!!!!

Comments

[janakaheshara]

Can we use this circuit for 24V fan?

[Easy and work project]

Change capacitor to 35 volts rate

[janakaheshara]

Thank you very much

[AttieP]

Thanks tried it and working , would I need to increase the Cap size if I add more than one fan ? if so can you suggest one .

[Easy and work project]

No, the cap use to set delay time. Mosfet use very low current so the cap current is not effect by mosfet. The mosfet can drain current enough for two or three fan or more(small heatsink require).

[telefonocastellano]

I have a Question. My Thermistor self-heats up to 72ºCelsius when I switch on the circuit. Is this normal?
Of course, the performance of the circuit is not as good as expected, the fans starts working at some point (30 seconds from circuit start) or at 45ºCelsius of the Thermistor head...

I can't really tell what is triggering the start of the Fans

[Easy and work project]

Recheck pin and check your variable resistor and use better quality capacitor.

[Skint007]

What would I need to change if I wanted to control a 110v fan in the same way? Wanting to install an exhaust fan in our network closet and would like the fan to ramp up/down depending on temperature this seems like a really neat approtch.

[Easy and work project]

This circuit work with DC fan only. You need another high voltage ac circuit for the fan

[Guile2912]

Would it work with 5v? If not, what part should I change?
Thanks!

[Easy and work project]

You need low vgs mosfet and 5 volts fan

[sum4all]

This is interesting project. I would like to try it. How do you set the threshold?

[Easy and work project]

I set the threshold by set air conditioner to the temp I want it to start (25c in the video) It's will rotating at slowest rpm @ 25 c