Panaflos don't like certain types of PWM

sthayashi · Post by **sthayashi** » Sat Aug 14, 2004 11:27 pm

I just wanted to let you all know that the Panaflo M1BX and L1A don't like certain types of PWM fan control. I know that this was discussed on a more general level including discussion of what PWM frequencies produced noise. But I feel that I should point out some specifics right now.

1) The Aopen AK79D-400VN motherboard uses PWM to regulate fan speeds. Unfortunately, it doesn't play nice with my L1A. At any speed, it buzzed more than when I plugged it into a linearly regulated (and seperately powered) fan controller.

2) I am 90% certain that the Shuttle SN41G2 machine uses PWM for its fan control, and I believe that it is also responsible for the major noise that is being produced by my M1BX that is in there. Tomorrow, I'm going to rig up a form of linear fan control to confirm this.

3) The Zalman Fanmate does NOT stop PWM noise.

Thank you, and I sorry if I'm restating the obvious.

HammerSandwich · Post by **HammerSandwich** » Sun Aug 15, 2004 11:36 am

sthayashi wrote:3) The Zalman Fanmate does NOT stop PWM noise.

Thank you, and I sorry if I'm restating the obvious.

That one sure ain't obvious!

greeef · Post by **greeef** » Sun Aug 15, 2004 11:46 am

http://www.bit-tech.net/article/51/1

details on how to build your own pwm controller, with frequency adjustment too!

It shouldnt be difficult to have a potentiometer and larger cap parallel across the frequency timing capacitor to make the PWM frequency user controllable. I just dont know what values to suggest..

I'm not expecting you to do this, but perhaps it would answer whtehr some fans dont like PWM at all, or if certain modulating frequencies just agitate certain resonances within the fan system.

griff

sthayashi · Post by **sthayashi** » Sun Aug 15, 2004 1:07 pm

Just to follow up, the M1BX that I had in the SN41G2 was NOT suffering problems due to PWM. It was just a bum fan that was loud all around. I replaced it with another fan and it was dead silent. But I plugged it into a 3-pin to 4-pin converter with a Fanmate on the end of it. It's nowhere near silent, but it's quiet enough for an HTPC.

So I'm less certain on the Fanmate affecting PWM than I was last night. But when I tried the fanmate on the Aopen board it wasn't as quiet as the cheapo linear regulator controller I plugged in a few days ago.

silvervarg · Post by **silvervarg** » Mon Aug 16, 2004 4:30 am

Putting a capacitor 1uF or 2.2uF in parallell with the Panaflo fan does help a lot to reduce PWM noise. It will however also lower the tourqe of the fan, so the minimum starting voltage should go up a bit.
This will more or less smooth out the PWM so it becomes something in between PWM and Linear regulation with some of the advantages and some of the disadvantages from both techniques.

cpemma · Post by **cpemma** » Mon Aug 16, 2004 2:50 pm

silvervarg wrote:Putting a capacitor 1uF or 2.2uF in parallell with the Panaflo fan does help a lot to reduce PWM noise. It will however also lower the tourqe of the fan, so the minimum starting voltage should go up a bit.

Same applies (including the drawback) if you put a small capacitor between base of the switcher transistor & ground, as described in Telcon's Application Note 58. It "blunts" the square wave.

sthayashi · Post by **sthayashi** » Mon Aug 16, 2004 4:14 pm

Putting on a capacitor means that I have to break out my soldering iron and electrical tape. I'll pass for now since I'm pretty happy with my current linear regulated methods.

Panaflos don't like certain types of PWM

Panaflos don't like certain types of PWM

Re: Panaflos don't like certain types of PWM