Potentiometer help. - Electronic Circuits Projects Diagrams Free

BlackOmega · 18th November 2008, 11:46 PM

Hello everyone, new to the forums.

Need some help with a potentiometer.

Im trying to make a manual fan speed controller for my computer. I bought a potentiometer from Radio shack and wired it in (#1pin input, #2pin output,#3pin ground). But it doesnt change the fans speed at all. All it did was lower the fan speed by about 300 rpms. Where did I go wrong?
Heres teh specs of the fan I am trying to control 12v,0.76A,9.1w.
The potentiometer I bought - 50k-Ω linear taper potentiometer, 500vdc-0.5w.
Is it wired incorrectly? Im kind of new to electronics and teh specifics of them so be gentle

-Omega.

SMUGangsta · 19th November 2008, 12:27 AM

I dont have my thinking head on today, but my first concern would be that your trying to control a 9.1Watt fan with a 0.5Watt rated pot.

My preffered solution for fan speed is Pulse Width Modulation, I use the followinfg circuit - it even comes with a stripboard layout in case your not very good with electronics.

Pulse Width Modulation 2

BlackOmega · 19th November 2008, 12:55 AM

Aha! thanx for that. It still looks a bit complicated, when I can find an electronics store near here Ill give that a shot. Im still bad with all the acronyms that are used. Its kind of hard to understand but Ill figure it out (stubborn that way). So basically, the pot I have is WAY too weak. I wasnt sure which spec to go by. Do they make 10w pots?
-Omega.

SMUGangsta · 19th November 2008, 01:11 AM

not sure about 10w pots, but id imagine if they did it would be huge and hot, running your fan at half speed, would mean dumping half the power through the pot, so its gonna get hot quick.

Some fans just wont start at less the 7v (according to that link) and you really dont want that, as the fan could stall and whatever is being cooled will cease being cold.

Have a look at a few of the links at the botom of the page i posted, they have many circits for fan regulation (thats what the sites about) and mabey there is something there to catch your eye.

EDIT: This link deals specufically with what you are trying to do.

Rheostats

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18th November 2008, 11:46 PM	#1
BlackOmega	Potentiometer help. Hello everyone, new to the forums. Need some help with a potentiometer. Im trying to make a manual fan speed controller for my computer. I bought a potentiometer from Radio shack and wired it in (#1pin input, #2pin output,#3pin ground). But it doesnt change the fans speed at all. All it did was lower the fan speed by about 300 rpms. Where did I go wrong? Heres teh specs of the fan I am trying to control 12v,0.76A,9.1w. The potentiometer I bought - 50k-Ω linear taper potentiometer, 500vdc-0.5w. Is it wired incorrectly? Im kind of new to electronics and teh specifics of them so be gentle -Omega.

19th November 2008, 12:27 AM	#2
SMUGangsta	I dont have my thinking head on today, but my first concern would be that your trying to control a 9.1Watt fan with a 0.5Watt rated pot. My preffered solution for fan speed is Pulse Width Modulation, I use the followinfg circuit - it even comes with a stripboard layout in case your not very good with electronics. Pulse Width Modulation 2 __________________ There will come a day when PICs will rule the world!

19th November 2008, 12:55 AM	#3
BlackOmega	Aha! thanx for that. It still looks a bit complicated, when I can find an electronics store near here Ill give that a shot. Im still bad with all the acronyms that are used. Its kind of hard to understand but Ill figure it out (stubborn that way). So basically, the pot I have is WAY too weak. I wasnt sure which spec to go by. Do they make 10w pots? -Omega.

19th November 2008, 01:11 AM	#4
SMUGangsta	not sure about 10w pots, but id imagine if they did it would be huge and hot, running your fan at half speed, would mean dumping half the power through the pot, so its gonna get hot quick. Some fans just wont start at less the 7v (according to that link) and you really dont want that, as the fan could stall and whatever is being cooled will cease being cold. Have a look at a few of the links at the botom of the page i posted, they have many circits for fan regulation (thats what the sites about) and mabey there is something there to catch your eye. EDIT: This link deals specufically with what you are trying to do. Rheostats __________________ There will come a day when PICs will rule the world! Last edited by SMUGangsta; 19th November 2008 at 01:25 AM.