How to Make a Simple Temperature Control Fan Speed

by Easy and work project

16K2023

Intro: 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!!!!

15 Comments

donni1 6 months ago

great video and instructions, thanks! I made this for fun today but
however much I tune the pot I cannot find the point where holding the
thermistor changes the fan speed, its always the same... any tips/ideas
why please? I used a 10k thermistor, 2.2uF 50v cap; irf540n mosfet; 12v
computer fan; 240v to12v transformer supply...

donni1 6 months ago

all good as finally found the sweet spot on the pot! and now comes on from a room temp. of 22 C as soon as I touch the thermistor, which at 10k is v. sensitive! excellent! thanks!

AttieP 4 years ago

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 3 years ago

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 3 years ago

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 3 years ago

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

Skint007 3 years ago

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 3 years ago

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

Guile2912 4 years ago

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

sum4all 5 years ago

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

Easy and work project 5 years ago

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