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Registered Member #1822
Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300
I wanted to build a setup where I would have a toggle switch I could use to select two different fan speeds for 10 fans seperatly. What is the best way to do this? They are 3 pin PC fans.
Registered Member #1822
Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300
Thanks for your help! The challange now is to find the correct resistor value. This is an excellent excuse to build a variable power supply out of an ATX PSU
Registered Member #1822
Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300
Actually, the purpose of the switch is to make the PC quiter during browsing but, full power cooling when ripping DVDs or playing games. This means that I will need to measure how much current is flowing when the fan is quiet.
Registered Member #2321
Joined: Fri Aug 28 2009, 05:13PM
Location: Boston, MA
Posts: 34
PC fans will stall if you underfeed them so that could have undesirable effects. Most fans will reliably run on 7V without stalling, below that you'll have to experiment.
For best quiet PC results,
- 120mm fans @ 1200RPM max - large CPU cooler with 120mm or greater fan
*One of my utility PCs is built like this, it's whisper quiet
OR
- PWM controller
Many new fans come with 4-pin connector, one extra pin for the PWM signal. PWM gives you best control range and you're not underfeeding the voltage.
cduma wrote ...
Actually, the purpose of the switch is to make the PC quiter during browsing but, full power cooling when ripping DVDs or playing games. This means that I will need to measure how much current is flowing when the fan is quiet.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
I've done the following:
The (+) side of the fan is connected to 12V, and with an SPDT you switch the (-) side to 5V of the PC power supply or ground, so the voltage difference is either 7V or 12V.
I've heard that it can cause problems with your power supply's output regulation. All I can say is that it didn't cause any apparent problems in my computer.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
Re: switching a load from a 5 volt to a 12 volt source across two poles of a SPST switch.
10 fans, parallel !
Just a page from 'old electricians bad dream' book-
Make sure the clearances in the switch are truely able to prevent the ark from the break of one pole from joing the ark of the make of the other pole, lest the two supplies get shorted together.
You could use a DPDT switch by connecting fans to both poles of the center terminals and the 12 volt supply to the left upper and the 5 volt to the right lower terminal.
Probably not an issue until you consider that a very tiny switch may be used.
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Fan Controller
