- Joined
- Dec 7, 2003
- Location
- Portland, OR usa
Here's a very nice link with a lot of information about fans & how to add very simple electrical components to slow them down.
(My apologies if it's been posted a zillion times.)
http://www.cpemma.co.uk/index.html
That's the link that finally explained to me exactly how a resistor drops voltage.
Simple how-to for slowing fans by 1/2 (12v to 6v) with a single resistor:
Summary: To drop fan voltage by 1/2 put in a resistor equal to the fan's resistance.
1) Calculate resistance of fan with simple formula. R = Volts/Amps. Volts and Amps are usually right on the fan's label on the hub. Volts for PC's is always 12v for fans.
2) Buy a resistor equal to 'R' ohms, above, of sufficient wattage. Needed wattage of the resistor is V * V / R, where V is the amount of volts being dropped (in this case 6, when working with 12 volts.) Buy a resistor with 2x the Watt rating it technically needs, so it doesn't get hot.
3) Put it inline with the fans power (black or red wire). Direction doesn't matter. Your fan will go from 12v to 6v, turn at half speed, move half the air, and sound half as loud or less.
Example:
I have a 0.25 amp Panaflo 120mm L1A. Resistance = 12/0.25 = 48 ohms. So I am looking for a resistor (approximately) 48 ohms. Watts for the resistor is 6v * 6v / 48ohms = 0.75 Watts. To be safe, I'll get a 2 Watt resistor, at about 50 ohms.
the problem with the resistor method is that it will drop *less* on a less powerful fan, and more on a more powerful fan. But it will still be approximately what you want, over a range of fans of different amps.
40 ohm resistor on 0.1A fan: down to 9v
40 ohm resistor on 0.2A fan: down to 7v
40 ohm resistor on 0.3A fan: down to 6v
You could also use the "7 volt mod" (described on that link as well.) However, putting in a resistor will be usable with mobo fan headers. I plan to get some fan cord extensions, and will make them into "volt dropping" extensions. Less wire clutter than the "7v mod" feeding fans off the PS.
There are also better ways to drop volts which are still fairly easy, described on that site, maybe I'll try some of them. Resistors are extremely cheap, though, compared to fan controllers. And small and unobtrusive
the wesson
(My apologies if it's been posted a zillion times.)
http://www.cpemma.co.uk/index.html
That's the link that finally explained to me exactly how a resistor drops voltage.
Simple how-to for slowing fans by 1/2 (12v to 6v) with a single resistor:
Summary: To drop fan voltage by 1/2 put in a resistor equal to the fan's resistance.
1) Calculate resistance of fan with simple formula. R = Volts/Amps. Volts and Amps are usually right on the fan's label on the hub. Volts for PC's is always 12v for fans.
2) Buy a resistor equal to 'R' ohms, above, of sufficient wattage. Needed wattage of the resistor is V * V / R, where V is the amount of volts being dropped (in this case 6, when working with 12 volts.) Buy a resistor with 2x the Watt rating it technically needs, so it doesn't get hot.
3) Put it inline with the fans power (black or red wire). Direction doesn't matter. Your fan will go from 12v to 6v, turn at half speed, move half the air, and sound half as loud or less.
Example:
I have a 0.25 amp Panaflo 120mm L1A. Resistance = 12/0.25 = 48 ohms. So I am looking for a resistor (approximately) 48 ohms. Watts for the resistor is 6v * 6v / 48ohms = 0.75 Watts. To be safe, I'll get a 2 Watt resistor, at about 50 ohms.
the problem with the resistor method is that it will drop *less* on a less powerful fan, and more on a more powerful fan. But it will still be approximately what you want, over a range of fans of different amps.
40 ohm resistor on 0.1A fan: down to 9v
40 ohm resistor on 0.2A fan: down to 7v
40 ohm resistor on 0.3A fan: down to 6v
You could also use the "7 volt mod" (described on that link as well.) However, putting in a resistor will be usable with mobo fan headers. I plan to get some fan cord extensions, and will make them into "volt dropping" extensions. Less wire clutter than the "7v mod" feeding fans off the PS.
There are also better ways to drop volts which are still fairly easy, described on that site, maybe I'll try some of them. Resistors are extremely cheap, though, compared to fan controllers. And small and unobtrusive
the wesson
