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PostPosted: Mon Aug 12, 2002 2:32 pm 
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Joined: Sun Aug 11, 2002 3:26 pm
Posts: 5
So the other night I assembled a thermal fan control device that varies the fan voltage based on the case temperature. I found the plans here: <BR> <BR><!-- BBCode auto-link start --><a href="http://www.heatsink-guide.com/antinoise.htm" target="_blank">http://www.heatsink-guide.com/antinoise.htm</a><!-- BBCode auto-link end --> <BR> <BR>It works like a charm - except that when the case temperature is low, the voltage supplied to the fan is also low, and before my Sunon 80mm fan has enough voltage to start turning it makes a horrible squealing noise. I need to fix it or disconnect it before my wife kills me. <BR> <BR>Has anybody else experienced fans making noise at low voltages? Do you know of any fans that don't make noise before they are started turning? <BR> <BR>Thanks for any help, <BR>Chris
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PostPosted: Mon Aug 12, 2002 2:32 pm 
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Joined: Sun Aug 11, 2002 3:26 pm
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Location: Coquitlam, B.C. Canada
Hello Chris, <br> <br>I have two thoughts: <br> <br>1. How old is the fan? If the fan is old, the bearings could be worn and at low speeds you are hearing the mechanical vibration. If the fan is new, this should not be the problem. <br> <br>2. Most DC fans today have a small micro-chip in them to control the fan speed. These micro-chips have a minimum and maximum tolerances to voltages. In my experiences as a technician, the noise you are experiencing could be caused by the micro-chip, as it is oscillating (the sound you are hearing) at the lower voltage and does not have enough energy to operate and regulate the small DC motor. <br> <br>I would suggest trying another fan. <br> <br>Good luck & good computing.
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