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How to wire a simple cooling fans circuit for a laptop stand, need an Expert help.

Hello everyone ! I am planning to build an extreme cooling laptop stand and I am encountering a problem during my tests phase.
What I want to do is to wire together:
- 2 x 92mm computer fans (12V - 0,6 Amp)
- 1 "B1K" potentiometer (or 2, one for each fan)
- 1 "O/I" switch (or 2, one for each fan)
- 1 12V power adapter (12V - 50-60Hz - 1000mAmp)

When I try to link 1 "B1K" pot with the 2 fans mounted in parallel, first the pot is almost useless (only 5% of its full course is useful) and second, it starts to heat and smoke...
What should I do ? Use 2 pots ? Or put in some resistances ? I am new with electronic and get lost with current / voltage / resistance... I thought this circuit would be pretty simple, but when I saw the smoke, I was frightened.

Any help / advice would be greatly appreciated.
Thank you very much.

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No, you can't use a pot. It causes the resistance of the supply to become so high, the motor can't get enough current to run.

Value of the pot has little to do with it. Controlling motor speed from a pot is a very, very bad way to do. it.

If you want to control speed, look for a solution based on a voltage regulator. The classic LM317 will work fine for you. All you need is one pot and one other resistor.

Steve
Openyourmind (author)  steveastrouk5 years ago
Hi Steve, thank you very much for your answer.
That sounds great. What would be the "other resistor" value ? And how should I mount all these together ?
Thanks again !
Jeff
Jeff,
Here's a great site with a built in calculator for you - and circuit diagram.

http://www.electronics-lab.com/articles/LM317/

Where they show a 5K pot, if you put a 2K pot in, the pot will adjust from 1.2 to 12V.

The LM317 will need a heatsink probably.

Steve
Openyourmind (author)  steveastrouk5 years ago
Hi Steve,

Thanks to your advices, it works !
It took me some time to make it works because, as I said earlier, I am new with electronic... and figure out what component is and where it goes, polarized or not, I should have said "I am VERY NEW with electronic" :-D

I have a couple of question though.
What is the role of the LM317 ? What does it do exactly ? How is it called (regulator, transistor...) ?

And I found 2 different layout for mounting this "LM317" on the web. One (the one you sent me to) uses 2 capacitors, and another one (https://www.instructables.com/id/Versatile-voltage-regulator-with-LM317/) which doesn't (see pict attached).
So my question is: what are the roles of the capacitors ? Are they really useful or not ?

I would be very happy if you can answer my questions.

Anyway, thank you very much once again for your advices.

Cheers !

Jeff
Assemble-the-circuit.jpg
Its a "voltage regulator". For your application, the capacitors aren't needed. If you were concerned with electronic noise, the caps would become more important.

Don't forget to mark mine as "best answer" !

Steve
Openyourmind (author)  steveastrouk5 years ago
Ok, I will check this website.
Thank you very much Steve, that's cool !
Vyger5 years ago
It must be a really slow night, I am the first one to even read this.
Anyway, fans actually can have a pretty high current draw. Its obvious your pot is way to wimpy. I think you would be better off to get a fan controller designed to handle the load. Something along the lines of this.

http://www.svc.com/ixa-fcin.html

Or just get one of the multiple controllers that fit in drive bays and dismantle it. They are pretty cheap anymore.
Openyourmind (author)  Vyger5 years ago
Hi Vyger,
thanks for your answer. Actually, I am NOT willing to buy a "ready to use" solution.
What I am looking for is to "understand" why this doesn't work... Can't I simply connect a 12V power supply, a pot and a fan ? Is there something odd here ?
I have access to stronger pots (B10K or B1M) but the result is worse...
Anyway thanks for your answer and the links.
Vyger Vyger5 years ago
Here is another one that does 2 fans and its the same price.

http://www.svc.com/zm-fanmate2-75.html