QiansonDC 12V 1A Automatic PC CPU Fan Temperature Control Speed Controller Case Fan Governor

Works quite well, it was lacking directions or for that matter any indication as to what connections where for power or fan. Eventually I located this helpful info

I had no problem setting this controller to my desired temperature and it ramps up and down perfectly. The board mounts with a single stud in the middle of the board, and the component leads stick pretty far out of the back; so the mounting options are limited. I just used some really thick double-sided mounting tape.Update: The controller ran fine for about a month and now it will randomly fail to start the fan as the temp rises. If I unplug it from the wall and plug it back in, it starts back up (at max speed sine the enclosure is an oven) and then ramps back down properly. This has happened several times with increasing frequency so now I don't trust it.

I attached the sensor to a heat sink and a cooling fan blowing at the heat sink. It seems that the design did not incorporate a hysteresis loop for different turn-on and turn-off set points. As a result, the fan turns on to cool the device, but moments later it turns off because the device is cooled below the set point, as soon as the fan stops, the device quickly heats up above the set point and the fan turns on momentary, then stop again .... and so the cycle repeats. You'll see that the fan turns on and off in short bursts continuously as the heat sink temperature vacillates around the set point. The overall setup works ok to keeps the heat sink from being too hot (that's why I give it 4 stars), but a hysteresis loop of two or three degrees built into the circuit will eliminate a lot of unnecessary fan stops and goes.

At first glance, it's a great product, but after trying it out, I came to realize it does not work well with the Corsair ML120 fan. The fan is constantly spinning faster and slower even though the temperature was constant. The reason is that the fan requires a constant 12v power while having the speed controlled via PWM, which this device does not support. It's still a great product and works great with most fans (i.e. 2 or 3 pin) but would not recommend with 4-pin PWM fans.

This controller did NOT work with the Intel 4-wire PWM fan I tried initially. As far as I can tell, this is because this control works by varying the voltage supplied to the fan, and, apparently, some PWM fans simply will not run with significantly less than 12V supplied to them.The controller did work with a 2-wire fan, one that doesn’t have PWM speed control. The inputs on the board are clearly labeled for the power input and output to the fan. One of the fans I tested has LEDs, so it needed over 7V to start the fan spinning—the board normally starts at 6V. Happily, you can use the adjustable mode (“A”) and get to board to output up to 9V at room temperature.