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I have recently learned about potentiometers and their "variable resistance" porperty.

I am looking to hook up a Potentiometer in order to control 4 12VDC Fans.

I am not sure if that is a good idea, but I would like to control all of them at the same time.

I currently have a PWM splitter that can split up to 8 PWM fans, so i know it's possible in some respect, but not sure if the resistance in the potentiometer is split across each 12v dc, which would affect which Potentiometer I have to buy I would assume?

Also, my fan has a 3 pin input (red, yellow, black) which, according to Which wire is negative on this PC fan?

Says "7v sensor" or "tachometric singal" so I'm curious exactly what that is for?

I do have a plug that split out into red/black, so I guess the Yellow has some purpose that isn't super important then?

Any advice is appreciated, thanks!

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XaolingBao
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  • Add a link for your "PWM splitter". You can't use a potentiometer to _directly_ control even a single fan (at least, not well), but if you are using PWM, it should be fine. – uint128_t Apr 02 '16 at 20:22
  • http://www.amazon.com/SilverStone-System-Cables-Black-CPF04/dp/B00VNW556I/ref=sr_1_3/192-3721801-5101334?s=pc&ie=UTF8&qid=1459628625&sr=1-3&keywords=silverstone+fan+splitter I've seen a few youtube videos and articles talking about hooking up a potentiometer to control fans, is this not correct, or just not a good idea as you said? My fans are 3-pin fans, so can I control them at all? I'm not sure exactly what the sensor is for... Thanks for your time. – XaolingBao Apr 02 '16 at 20:24

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I am looking to hook up a Potentiometer in order to control 4 12VDC Fans. I am not sure if that is a good idea...

Well, controlling a fan with a potentiometer directly is a bad idea. First off, your control will be very non-linear; secondly, you will be dissipating a lot of power in your potentiometer, and unless you have a very large (and therefore bulky and expensive) pot, it will fail (most pots are not designed to dissipate lots of power, and the ones that are are huge).

However, you can use the pot to control PWM driver that controls the fan speed efficiently. This is how your computer motherboard controls the fan speed. And once you have that PWM control signal, you can use that PWM splitter you linked to control many fans.

However, you may have an issue: some fans have four wires and some have three. Three wire fans have +/- supply and a tach signal (more on that below), while four wire fans have a PWM input as well. If your fan doesn't have that PWM input, I'm not sure that product you linked will work well. See this answer for more.

You'll need a PWM fan control circuit, or you can buy a pre-built PWM fan controller.

Also, my fan has a 3 pin input (red, yellow, black). Which wire is negative on this PC fan?

Says "7V sensor" or "tachometric signal" so I'm curious exactly what that is for?

Red is positive supply voltage (which can be PWMed for speed control). Black is ground. The yellow wire is a tachometric signal, it outputs pulses that let the driving circuit monitor speed. See this question and the excellent answer for more info.

uint128_t
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  • There are also transformers that have variable voltage outputs. I've used one for one 12VDC muffin fan. It had a built in slider pot. It worked fine. But, four....could be stretching it. – Tim Spriggs Apr 02 '16 at 20:50
  • Than ks for the info, but for this project I have 3 pin fans. @Tim, I am not sure on the total amount, but I wanted more than 1, but will be testing to see how much airflow I really need.... So the potentiometers are a bad idea then for this project??? Is there anything else I could use that's a good idea? these fans running at full speed are most likely going to be very loud, so I want to silence them a bit, but I guess we will see how loud they really are. FWIW they are Noctua 40mm fans. – XaolingBao Apr 02 '16 at 21:49
  • There are probably a lot of COTS PWM fan controllers that will work with three pin fans. – uint128_t Apr 02 '16 at 22:29
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So the potentiometers are a bad idea then for this project???

Using a potentiometer directly is a bad idea even for one fan. Even worse idea for multiple fans. That is exactly why they make controller boxes like your SilverStone CPF04

Is there anything else I could use that's a good idea?

Your SilverStone CPF04 says it will control up to 8 fans. It is not clear why you don't simply use that?

Richard Crowley
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  • I use it for my PWM 4-pin fans, but I am using a 3-pin fan(s) now on another build. I wasn't sure if the fan controllers would work on 3-pin fans, or just 4-pin fans :) Alot of the fan controllers don't sem to really be that good either... How exactly are they made? A lot more complex? – XaolingBao Apr 03 '16 at 00:33