Voltage controller influence on PSU? - Techist - Tech Forum

 Techist - Tech Forum Voltage controller influence on PSU?

 01-27-2010, 04:31 AM #1 (permalink) Super Techie   Join Date: Apr 2004 Posts: 274 Voltage controller influence on PSU? I was thinking to do a controller for fans by installing a switch to make fans run on varible speed as follows: 12v regular (+12 and ground) 5v redused (+5 and groung) But i thought maby its better to raise the lower speed a bit , stil no noise but more air: 7v moderate (+12 and +5) Will it do any negative effect on a power supply in a such configuration especially in 7 volt application??? (I have 5 fans in Element S case, who together draw about 1.5-2 Amps at stock) __________________ __________________
 02-01-2010, 11:12 AM #2 (permalink) Ultra Techie   Join Date: Jun 2005 Location: Spaceballs Mega-Maid Posts: 783 Re: Voltage controller influence on PSU? It shouldn't have any negative effect on your PSU, assuming you wired it up correctly. I would just connect a potentiometer to the 12v lead of the fan. __________________ __________________
 02-01-2010, 03:39 PM #3 (permalink) Lord Techie     Join Date: Feb 2009 Location: Florida Posts: 7,946 Re: Voltage controller influence on PSU? You could use one of these for converting the 12v to 7v. And no, it won't affect your power supply. 7 Volt Fan Speed Resistor __________________ [SIGPIC][/SIGPIC]
 02-03-2010, 07:33 AM #4 (permalink) Techie Beyond Description     Join Date: Jun 2003 Location: Melbourne, Australia Posts: 14,559 Re: Voltage controller influence on PSU? Just add a resistor of appropriate resistance V = IR fans typically run at 0.2A, and therefore have a resistance of 12/0.2 = 60 to run it at 7V, find the current required, which is 7/60 (V / R) Then calculate the value of the resistor needed for a (12 - 7 = 5) volt drop 5 = (7/60)*R 5 / (7/60) = 42.85 ohms __________________

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