Wriring Comp Fan in Hood

kfowler · 12/15/2006, 08:06 AM

I have a 120mm computer fan that I wired to a DC tranformer. The fan runs great but it runs full speed all the time and I would like to reduce it to a less audible level. The fan has three wires. Red, yellow and black. I currently have the red and yellow wired together to the hot wire from the transformer. I've read that the yellow wire is typically your speed control wire. If so, is there a way I can wire this to control my fan speed. Like can I get a speed control devise from Radio Shack? If so, how do I rewire this.

cubber · 12/15/2006, 08:18 AM

Since you are using computer fans why not use a fan speed controller made for computer fans. Check out these links for some examples.

http://www.directron.com/speedcontrol.html

http://www.pccasegear.com/category18_1.htm

Not sure how you would wire them in your situation, but I think if you figured out how to wire the fan they shouldn't be a problem since they would use the same molex connector that the fan typically uses to connect to a pc power supply.

Driftwood · 12/15/2006, 08:35 AM

One easy way would be to get a lower voltage transformer. Try a 9v transformer and it will turn slower.

kfowler · 12/15/2006, 08:42 AM

As Mr. Burns would say "Excellent."

I'm curious how the 12V to 7V cables work. I tried running my fan at 6V by switching my multi-adapter to that setting. It burned it up. Not a good idea.

pjf · 12/16/2006, 05:58 AM

Quote:

Originally posted by kfowler
The fan has three wires. Red, yellow and black. I currently have the red and yellow wired together to the hot wire from the transformer. I've read that the yellow wire is typically your speed control wire.

The yellow wire is not a speed control wire. It is an RPM sensor wire that allows your computer motherboard to determine the speed of your fan. Some motherboards can vary the speed of the fan by varying the voltage.

There are 4-wire fans known as Pulse Width Modulation (PWM) fans. These fans have a additional blue wire. Instead of varying the voltage to control the fan speed, a PWM controller will feed the fan an ON/OFF square wave. I don't recommend these fans for a hobbyist because at certain speeds, you will hear noise from the fan clicking on and off. Another disadvantage is that the RPM sensor will not work on a PWM fan unless the fan is running 100%.

12/15/2006, 08:06 AM	#1
kfowler Premium Member Join Date: Dec 2003 Location: Michigan Posts: 1,095	Wriring Comp Fan in Hood I have a 120mm computer fan that I wired to a DC tranformer. The fan runs great but it runs full speed all the time and I would like to reduce it to a less audible level. The fan has three wires. Red, yellow and black. I currently have the red and yellow wired together to the hot wire from the transformer. I've read that the yellow wire is typically your speed control wire. If so, is there a way I can wire this to control my fan speed. Like can I get a speed control devise from Radio Shack? If so, how do I rewire this. __________________ Kevin "You cannot achieve what you are not willing to pursue." Current Tank Info: 20g Mixed Reef

12/15/2006, 08:42 AM	#4
kfowler Premium Member Join Date: Dec 2003 Location: Michigan Posts: 1,095	As Mr. Burns would say "Excellent." I'm curious how the 12V to 7V cables work. I tried running my fan at 6V by switching my multi-adapter to that setting. It burned it up. Not a good idea. __________________ Kevin "You cannot achieve what you are not willing to pursue." Current Tank Info: 20g Mixed Reef

12/15/2006, 08:18 AM	#2
cubber Registered Member Join Date: Jun 2006 Posts: 311	Since you are using computer fans why not use a fan speed controller made for computer fans. Check out these links for some examples. http://www.directron.com/speedcontrol.html http://www.pccasegear.com/category18_1.htm Not sure how you would wire them in your situation, but I think if you figured out how to wire the fan they shouldn't be a problem since they would use the same molex connector that the fan typically uses to connect to a pc power supply.

12/15/2006, 08:35 AM	#3
Driftwood Registered Member Join Date: Jan 2006 Location: Gardiner, ME Posts: 841	One easy way would be to get a lower voltage transformer. Try a 9v transformer and it will turn slower.