Question Best way to control fans without motherboard

B!gMeme

Commendable
Sep 14, 2020
50
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1,545
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My system does not have PWM headers for case fans, so I have been searching for temperature-based fan controllers. I have come across a kit board that does precisely this, albeit using a thermistor, which can only read the ambient case temperature: https://www.amazon.com/gp/product/B077SLWWXL . It seems like a good option, but, at the same time, I wonder if there is a board that can control PWM speed using a USB connection and some software. I am proficient in programming, so I don't necessarily need an end-user-friendly option either. I have searched for this so-called USB-controlled PWM board to no avail. I don't want to use an Arduino, because the breadboard will make the setup bulky. Maybe somebody here has seen something?
 

Lutfij

Titan
Moderator
If you have a PWM fan header on your motherboard(for the CPU_FAN) you can get a PWM fan hub, that only means that all fans will ramp up or die down according to CPU temps. You might be able to get away with a fan curve if your motherboard allows an end user to manipulate fan curves, i.e. Make and model of your motherboard and the fans in your system?
 

B!gMeme

Commendable
Sep 14, 2020
50
12
1,545
1
I can technically get away with this, but I would prefer if I could get my fans to ramp based on GPU temperature. I already have a hub, I am just trying to see how I will control the speed. The only way I could link this to GPU temperature would be by somehow controlling them via USB.
 

Paperdoc

Polypheme
Ambassador
Basing case fan speed on the temperature measured in the graphics card on the GPU chip is quite uncommon and has two major problems. The practical one is: how do you measure the temperature? Almost all graphics cards DO have temp sensors built into the GPU chip and they USE that info to do control their own cooling fan. BUT there is NO standard way to get that temp reading out of the graphics card for use elsewhere. The graphics card maker often does half this job in their own proprietary software utility to DISPLAY that temp for you. But that does NOT give you (or your custom fan controller) that same info in electronic form that you can use. And I can assure you that trying to fasten an external sensor to the GPU chip in the right spot and keeping it stuck there reliably is difficult and MIGHT risk damage to that chip.

The second problem is uncontrolled interaction of TWO control systems. The card VERY likely has its own internal method of controlling its fan according to the temperature of the GPU chip. If you now add a second external means of controlling the flow of cooling air for that GPU chip (your proposed case fans), those two systems will constantly interact and "chase" with each other. One system will decide the temp is too low and slow down, and a short time later the other system will make the same decision and slow itself down, and then each system at different times will recognize a temp rise and speed up again. Or sometimes the second system will think the first one over-acted and will try to act in the opposite direction.

The common system that does work and avoids these problems is that the CASE fans are controlled according to a temperature sensor on the MOBO, and that system is already "tuned" to keep that sensor cooled properly. Doing this ALSO ensures that there is a good supply of cool air inside the case that the graphics card's own fan can use for its purposes. So each of those systems, while concentrating on its own needs, assists the other with NO direct interaction and no danger of counteracting each other.
 

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