Subject: Fan Temp Control - Noisy
By: Derek (IP: 124.168.45.*)
Written on: 20-02-2008 03:57


I\\\\\\\'ve built the fan temperature control described on this site and everything works perfectly except for some high frequency noise before the fans start.

This noise occurs as the temperature slowly approaches the \\\\\\\'fan on\\\\\\\' set point so I suspect is a consequence of the fans not having enough voltage to start. As these are brushless DC motors I\\\\\\\'m guessing it is something to do with their internal circuitry that is the cause of the problem.

Is anyone else having this problem or does anyone know how it can be fixed?

Thanks for any advice.

By: rockman20 (IP: 165.234.180.*)
Written on: 05-03-2008 20:58

I have the same issue. Mine is a little more pronounced because I have been running 4 fans on one controller. (I am using mine in an entertainment center) I plan on building another one and split the fan useage up because the transistor gets VERY hot with 4 fans. I have installed a heat sink on it which helps to get the heat away, but I fear that it will burn out sometime.

I would love to know of a way to get the fans to quiet up right before start up. I am by no means an electrical genius at all. I know enough to build a circuit if given directions and enough to melt and fry a lot of stuff. :-)

I would think though that perhaps a capacitor could take care of this? But I wouldn\'t even know where to begin to figuring what size of one and where to put it in the circuit.
By: rockman20 (IP: 165.234.180.*)
Written on: 12-03-2008 19:13

I have played around with some CAPS and I even played with the idea of a relay. I thought for sure that the relay would be a great way to control many fans on one controller since all the controller would be doing is turning the relay on and off.

The relay works. But if you think the hum of fans is annoying, don\'t hook up a relay! I never knew a relay could flick on and off so fast before now! It\'s amazing!

The CAPS I couldn\'t get to work, but I am sure that I am wiring them up wrong.

The one thing that I am going to do is this. I noticed that if I held the fan in my hand, it made little to no noise then if I set it on the table. So, I am going to look at creating a rubber mount for my fans in my entertainment center. I am hoping that will eliminate a lot of the hum that I hear on startup.
By: Derek (IP: 124.168.35.*)
Written on: 13-03-2008 00:36

I should have heeded the advice given about the quality of the fans! See the section on \"Cooling fans\" in the sidebar on the left.

Apart from the noise before the fans came on, I was also not happy with the running noise of the cheaper fans original selected for the job. I too am using the fans to cool a home theatre cabinet. The PS3 runs hot and its fan is quite noisy so I wanted it in a cabinet with everything else.

So I forked out for two Papst fans (Model 8412NGL) and WOW, these babies are quiet and the noise before they start is much much less than on the cheap ones. I guess the control circuit inside the fans is better in the Papst fans. And they really are individually balanced with little weights.

But, being a little obsessed with this project, I also played around with capacitors with some further success. I managed to almost eliminate the pre-startup noise by placing a 330uF capacitor across the fans. If you are going to do this yourself, make sure the capacitor is rated to at least the voltage of the fans and be aware that capacitors have a positive and a negative end.

You might be able to use a smaller capacitor than 330uF but I didn\'t get any improvement with values down in the 10 uF range and below. It will probably depend on the number and type of fans that you have.

By: rockman20 (IP: 24.119.247.*)
Written on: 19-03-2008 03:09

Thanks for the advice! I may have to play with the CAPS a bit more. For now I am just running 2 fans on one controller. I purchased another thermistor and MOSFET for a second controller to control the other two. I am going to work at rubber mounting these fans also to try to keep the noise from traveling into the entertainment center. I found that if I hold the fan it makes far less noise then when it is mounted on the back of my entertainment center. I suppose the back acts like a megaphone.

I have the same issue with my PS3. Right now I have everything behind glass doors. My stereo equipment is on a top shelf and the DVR, DVD, PS3, old school Nintendo, and controller charger is on the bottom shelf. I have two fans for the lower and 2 for the upper. 2 fans blow cool air in and 2 fans blow the hot air out. It works pretty well at keeping the temps down inside with just 2 of them running now. (one in and one out) It should be nice and cool when I get the other two hooked up. Hopefully this weekend.

Thanks for the tip on the caps though. I have a whole container of them here and will search through and see if I have anything big enough to handle the draw.
By: meyer (IP: 68.206.128.*)
Written on: 04-07-2008 02:01

HELP!! My fan is suddenly stuck on run high. Any ideas????
By: Anonymous (IP: 58.6.5.*)
Written on: 27-07-2008 07:28

The transistor might be overheating. I had similar trouble when I tried to control a 60 x 60 x 25 (millimeters) axial fan (no connector, just stripped wires) from an electronics workbench. The fan starts at 4.5V, which is amazing for a 12V fan as most 12V fans need a least 7V. It isn\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'t faulty, it\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'s using too much electricity, it uses 133mA but the transistor (a small NPN bipolar transistor) can only handle 1-2mA constantly. I touched the transistor, and burnt my finger. I\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'m very sure it can\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'t even handle 40mm fans. But who knows...
By: Karmar (IP: 121.45.52.*)
Written on: 21-04-2010 16:29

rockman20 posted earlier
[quote][B]\"CAPS I couldn\'t get to work, but I am sure that I am wiring them up wrong.\"[/B][/quote]

Has anyone figured out the CAPS to remove the noise or worked out any other way?
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