Re: 4-pin pwm fan.

I work as a coputer tech (fixing pcs) in a major university as part of

> a work study program. Im also a junior in computer engineering, so I > know my way around a breadboard. > > One of the machines is a newish dell btx, that's having major cooling > problems (random page faults, hd temp goes up to about 130 F, etc). I > narrowed the problem down to the main case fan, which is a four pin > PWM (pulse-width modulation). Apparently, the bios (happens without > hd/os) forces the fan to spin at a ridiculously low speed, > approximately 10% of capacity. After tinkering a bit, I found that > cutting the blue (PWM) wire was adequate enough to disable pwm, and > forced it to 100%. But now it sound's like one of those handheld > vacuum cleaners, and is likely to have a very low MFT (mean failure > time). I've tinkered a bit more, and found that by grounding the pwm > with a suitable resistor, it slows it down to an acceptible level. > I've run a few tests, and I've come up with the following data: > > Fan Power draw at 100%: ~375 mA > Ideal Power draw (flow vs sound): ~210 mA > > Pwm voltage (fan to ground): ~3.266 V > Pwm Current (directly grounded) ~0.52 mA > Ideal Pwm>Resistor>Ground: ~3.2 kOhm > > I was wondering if anybody had any additional input about this before > I screw something up royally. With these Ideal values, everything > seems to work fine, and I don't notice any risky voltages or > currents. I'm on a tight schedule, so I'm likely to begin soldering > everything into place soon. > > Cheers.

The fan should run just fine at full power without significantly shortened life.

You can get small fan speed controllers that are standalone, they're cheap.

Reply to
James Sweet
Loading thread data ...

I had a noisey fan like that once and put a resistor in series with it to make it run at 9V which was much quieter. It ran for years and is still fine.

Reply to

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.