Smoothing a PWM controller for electrically noisy fans?

[Mpegger]

I have a number of fans hooked up to my Sunbeam Theta fan controller (long discontinued) which works via PWM to control the fans. As you know, some fans don't work well via PWM, and will make (very annoying to me) electrical noise when running on anything lower then 100% duty. I have 2 such fans which I cannot easily replace (220mm) that I want controlled by the Theta.

I was wondering if there was some way to take the output of the controller for that specific channel/fan, and have it smoothed so that the fan is receiving a non-pulsed voltage to eliminate the electrical noise?

 

[Diggrr]

The fans themselves are 3 pin, right?, like the newer Sunbeam does?
Sounds like a job for a smoothing capacitor between the + and - fan lead.
No clue as to what size, I'd try a random one from the desk drawer myself, just not a tiny little thing for the amperage involved. I use old power supply caps I recycled for my odd projects.
Use a fan extension cable to test, then you don't mess with your fan's tail, keeping that original.

**For the record, I'm far out of my depth here. I smoke parts on occasion too. But I'd try it...maybe with a cheap no name fan first!

 

[Mpegger]

The fans are all 3 pin, as is the controller. So just the normal +12V, Ground, and Tach for each fan. I think your idea is sound, I just dont have any caps laying around to even attempt to try, nor would I have any idea what values to buy at the local Radio Shack (if they even still carry capacitors). Anyone with more knowledge/experience in circuits care to chime in? I really want to lower the fan speed on those two to help reduce noise further.

 

[Diggrr]

Well good news and bad news.
I went ahead and tried the smoothing cap idea on a Panaflow (NMB) 92mm that's always sounded like it's grinding coffee when it's speed throttled.

At full throttle, side by side with a matching fan, you could hear the unmodded one raising and lowering rpm (dropping in and out of resonnance with the modded one) so the modded one had a steadier RPM.

Other good news, installed on a motherboard, RPM reporting also showed a steadier RPM too.

Bad news, still sounded like it was grinding coffee (this mobo throttles even on the 3 pin headers).

So, while it has steadier RPM, it doesn't make a noisy fan more gooder.

**680μF 200V PSU cap...I tried

 

[Mpegger]

Thanks for the info. I remembered that I have a couple of Zalman Fanmate 2s boxed up somewhere and am gonna try one of those between the fan and the controller and see if that helps cut down on the fan noise. It's a little more then just a capacitor, so I'm hopeing that it'll work somewhat.

 

[ehume]

Some fan controllers do PWM by interrupting the 12 Volt current flow. I suspect you will always get noisy fans that way, some more than others. OTOH, some fans just make noises when they are undervolted. And some fans just grind away all the time, like my own Panaflo. I'm glad to see I'm not the only one to observe the coffee grinder effect.

These fans all have PCB's inside. I have found a good way to check for clicking (the sound of switching) is to run 5 Volts through the fan. Then you have a lower voltage that is not mediated by a fan controller. If the fan clicks then, you know that any search for a quieter fan controller will be fruitless.

 

[Diggrr]

Using the same Panaflo, I can hook it up with a 10 watt resistor inline with a desktop PSU and it's rather quiet (until you rigidly mount it). Sitting on my mouse pad, you have to be withing 10" to hear it at all.

If memory serves, PWM was originally seen with the motherboard handling all the switching. Sometime afterward the 4 pin fan came out with the fan doing the switching internally. I'm sure my board does the PWM onboard like the original.

Not a perfect solution (especially considering you already bought a controller) you might try the 7 volt mod to see if you can quiet your growlers.
I'm pretty sure the Sunbeam is taking PWM and applying it to the 3 pin sockets (like the old days), and it just doesn't agree with some fans.

It's probably easier to replace the controller with a resistor type (if the 7 volt mod works quietly) or to replace the fans with PWMers, cause there's almost no way to tell until you've bought/tried them unless someone else pipes in with a Sunbeam running a brand that happens to be quiet.
That's all I got, bud!

 

[Mpegger]

Well with the Zalman FanMate installed inbetween the controller and the fan, using the controller to try and lower the fan speed I still get the noise. Keeping the controller set at 100%, and using the FanMate to control the voltage, the fan does not make noise when undervolted. Obviously, these two fans work fine with undervolting, but not when its PWM method.

It may be time for me to ditch the Theta controller and get something more modern.

 

[Diggrr]

If it's just two fans that are close together, I'd use a DPDT toggle switch, one way being 12v, the other 7V.
The original fan controller IMHO, from years back. Easy to wire too.

But at least you have the problem isolated now!

 

[Mpegger]

If it were that simple I'd have already done it.

The reason I purchased the Theta, was because it controls the individual fans according to the thermistor probe attached to that fan port. I set the low/high temp range in the software, and the hardware controls the fan speed accordingly. My room is not climate controlled in any way, so temps vary widely according to the ambient days temp. I also use my computer for everything, from just plain browsing the web, to gaming, encoding, etc, etc, so temps for the system hardware can also vary. I ditched the manual controllers for an automatic because of having to constantly have to adjust each fan manually for whatever I was doing, as well as the current air temps. I'd rather just set a range that works well with my hardware in keeping the temps under control as well as the noise, and forget it.

That being said, the only controller I'm finding that seem to fit the bill is the T-balance bigNG. Can control via PWM or "analog" (as they put it) and can interface with other monitoring programs. Can also be used with a water pump (something I'd like to start doing since my pump is getting on in age) and even shutdown the PC in case of pump failure. Only downsides are the pricetag (need to get add-ons for pump) and that it only has 4 fan controller ports without the add-on.

 

[Diggrr]

Gotcha.
I lucked out really, the Lian-Li fans do just fine on the motherboard controller...my tiny case only uses the two fans.

Good luck finding spare funds these days mate!

 

[ehume]

Well with the Zalman FanMate installed inbetween the controller and the fan, using the controller to try and lower the fan speed I still get the noise. Keeping the controller set at 100%, and using the FanMate to control the voltage, the fan does not make noise when undervolted. Obviously, these two fans work fine with undervolting, but not when its PWM method.

It may be time for me to ditch the Theta controller and get something more modern.

Thanks for running that experiment. It's very important for our collective understanding of fan and controller dynamics.

I note you are using a Gigabyte board. There should be a BIOS setting for adjusting fan speed with Voltage automatically. That might work for your cpu fan and your chipset fan.