I have two types of DC 12V CPU fans, type AFC0612DE (Delta Electronics) and TA350DC (Nidec).
Both types have PWM pins for speed control. I however do not have a controller.
I would like to set the speed of these fans to something other than the max speed while not having to build a PWM controller to control the speed.
My input power comes from a 220VAC – 12VDC ~2A transformer.
I have tried putting a 450 ohm resistor before the fan, this makes the fans not start at all.
Having two fans in the circuit either serially or in parallell also makes the fans not start at all.
My concern is the noise from the fans when they run at maximum speed, I could have two fans if that would work, only if they don't run at maximum speed.
Is it possible to modify any of the static input parameters to change the fan speed? I have some old VCR, PC parts that might contain the missing things, so tell me what I need and I'll see if I can find it.
Best Answer
I added fans to the backs of my computer monitors to allow them to run cooler and hopefully extend their lifespan. I used computer CPU fans similar to yours that have the 4 wire connections including the PWM input. To lower the noise and be able to control the fan speed I built a simple little box that takes in 12V from a AC->DC wall type power module and then outputs that to four fan connectors on the back of the box. Internally I designed a very simple circuit that runs off 12V and uses two 555 timer chips to produce a 22KHz requency waveform and then uses a pot on the second 555 timer chip to create a PWM signal to drive the four fans.
I'll post a picture of the schematic later so you could use the same design if you wish.