12v chassi fan

How can i control speed of an 12v chassi fan from openhab?

some sort of relay?

Think the Shelly’s operate at a choice of voltage that includes 12v

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If you are running Linux I recommend lmsensors. I control 12v fans on a mining rig using a bashscript and exec binding. See https://wiki.archlinux.org/index.php/fan_speed_control#Fancontrol_(lm-sensors)

Where i need the fan is not close to any computer.
Was looking into https://robotzero.one/esp8266-fan-speed-control-ds18b20-temperature-sensor/
and have one-wire from openhab.
But i will investigate shelly then i will have all of this in one unit and can run rest over witi.

I think ESP8266 is a good option, then you can control and read temperature in the same unit… Combine that with a 12V relay and you should be good to go.

See my fogmachine setup it’s more or less the same for 12V. Cheap FOG Machine for Halloween controlled by OpenHAB

The shelly route might be simple. A Fibaro RGBW could do the same job (dimming 0-12V).

Regards, S

It’s depends what kind of fan you have 2 pin, 3pin or 4 pin.
in 2 pin fan you can change speed by changing voltage.
3 pin it’s the some like 2 pin, on additional third pin you can read RPM (2 pulses per revolution) usually a Yellow wire.
4 pin it’s PWM conntroled, similar to 3 pin red and black is allways full 12V DC, yellow RPM, and additional wire for PWM (Pulse Width Modulation). This is a square-wave signal at 25 kHz frequency with variable fill and this conntrols additonal chip in fan.
Conclusion, you can’t use PWM for 2 and 3 pin fans they will behave like speaker, you will hear PWM signal it’s very annoying :). Controling 4 pin fan with LED dimmer is not good idea, they are not for induction load so can be demaged. With frequency other then 25 kHz fan can work or not.

Regards Rafal