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Stupid simple temperature controlled pc box fan driver. 2013-01-13

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()blivion submitted a new article:

Stupid Simple Temperature Controlled PC box fan driver. - Hello and welcome. Feel free to skip any sections you don't want to read. To make this circuit work

Hello and welcome. Feel free to skip any sections you don't want to read. To make this circuit work you really only need the schematic picture and some of the text after it. The "over explaining" is for new people who want to fully understand what is going on here, and are willing to take the time to learn. If you are an EE type already, and feel that I have made an error somewhere, PM me with the details. (I *DON'T* care about correct spelling and grammar, {or idioms... apparently} like......
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Active Member
Me and jocanon corresponded by PM already about this, but I want others to know the answer as well.

The NTC thermistors he links to and units like it are perfectly acceptable. The only requirement for your NTC thermistors is that it must be intended for temperature use and be around 10K ohms. Though the units linked above look similar to the ones I say not to use, they are not the same. Serge suppressor NTC's are very low resistance and physically very large, they get hot when power goes through them, then they drop resistance to virtually zero because of that heat. They are not heat sensors, they only use the same physics and have the same name, IE "NTC thermistor".

Simply make sure the ones you purchase are for heat detecting and you should be fine.


Thanks ()blivion! I used this ciruit on a PSU fan and it works great. ()blivion has been very helpful. Since I am new to building circuits (this was my first one) I needed a lot of help and this write up was just what I needed...thanks again.


Dude, coo; write up. Just learnin the lectronic's stuff and this was a great project to cut my teeth on. I scrounged all of it except the multiturn and it does great for a fan control circuit for my brew computer. As it heats and cools the fan speeds and slows proportionally to the current interior and component temps. Great lil starter design to tinker with and learn about adjusting different values to get an optimum set up. Thanks!!!
Wheelchair Bob


Active Member
NP every one, and thanks for the compliments. Did this as much for me as I did for the community. If I could, I would like to clean it up a bit still. But I can get busy and I find other things to do from time to time. So I may never do anything more with this. Hope it's good enough as is.


New Member
()blivion, hi.

I like your 'give it a bash' approach!

I came by here looking for a hints on a way to modify a switched solar thermal pump controller to make it provide variable pump speed in response to temperature difference (rather than just coming on at threshold difference) my 20-year-old electronics schooling is pretty rusty ("and I've got a terrible pain in all the diodes..."), but do you think I'm on the right track combining you circuit with the differential controller, or would I be better off starting from scratch?



Active Member
Hi Jack.
Glad you like the approach. I figured giving part numbers and exact plans would ruin the grace of the circuit. Which is that it will work just about anyway you can build it. So long as you understand it.

Your question:
If I had to take a guess at it, I would say you should be able to just use my circuit as is. The only part you may have to change is the MOSFET, possibly to the one from the circuit in your link. What ever you do, get something with as high Wattage as you can find. You may have to put it on a heat sink also depending on the size of your pump. Any big piece of metal should do fine.

The above being said, generally when doing anything "alternative energy", one is always trying to conserve power. Unfortunately, that is the one thing this circuit is not very good at. This is because a significant fraction of the controlled devices power is lost in the MOSFET when running in any mode other than fully on, or fully off. And this circuit is designed specifically to run exactly in this "in the middle" way. This is not as much a problem with PC fans as the amount of power we need to control is minimal compared the power use of the whole PC. However, a water pump of any moderate size will use significantly more power, and should thus be an important concern for you.

The best way to control your pump would be to use a low power PWM circuit in the >30Khz range. Hit the forms and you should receive tons of help with this.

Hope this helps.
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