120mm Fan Testing on an MCR120 Radiator Round 6

[Martinm210]

in the circuit described in this link, a transistor to switch the ground line of the fan (low side switching) is used. would be a big surprise if you get usable rpm readings this way. recommend to use so called high side switching, which is connecting the transistor between +12V and the fan. but you need a different type of transistor here and probably a second transistor to shift voltage levels.

also i expect you will run into the same problem i did, which is very limited rpm control. in this circuit ability to control rpm is also highly dependent on load (fan current rating).

but give it a try.

as already stated in another thread (#33 #36 #54 so far), required power (wattage) is totally overrated. even the most demanding fan in your tests here (Delta AFB1212VHE) will produce less than about 2.5W power dissipation in the controlling transistor. look for my postings in this thread for more details on issues with PWM control.

efficiency:
trying to save 1W maybe 2W per fan seems nonsense to me, when we are using systems which burn several hundreds of watts in total!

heat:
same here, it should not be that big of a deal to get rid of this additional few watts generated by the fan controller.

analog fan control on the other hand gives you easy rpm control independent of fan current rating and also usable rpm readings at very low rpm.

but that's my point of view, others might be more particular here ...

Awesome, thanks!

I've got some reading to do... Having a ton of fun building these mini circuits, so even if I fail, it's all good fun and likely a good learning effort at the same time.

The only reason I'm exploring PWM and alternative controlling methods is to see if there is any difference in how the fans react. But really...I'm just using this as an excuse to play with my electronics learning lab....