PWM fan off

So i want to build some sort of controller based on adruino, that would shut off fans below a certain pwm value, that motherboard sends.

I would like to build a semi passive system, but motherboard sadly does not support lowering the pwm value below 20%. So the idea is, that use arduino to catch the pwm signals from the motherboard. Everything below 20% would forward 0% to the fan, but anything higher than 20% would forward pwm as it is (for example 50% would be forwarded to fan as 50%). This way i retain motherboards control of fan speed while gaining fan off feature.

Is something like this possible with arduino ?

hojnikb: Is something like this possible with arduino ?

Yes, your problem consists of 2 parts: - Reading the duty cycle of a pwm-signal. - Producing a new pwm-signal.

It should be easy to find information about these tasks. Be aware though, that fans do not always start up as intended, that's why your mainboard never stops them completely.

lg, couka

it might be impossible without bypassing the motherboard control altogether... When the motherboard senses that that fan is not moving it might crank-up the PWM until the fan comes-on.

DVDdoug: When the motherboard senses that that fan is not moving it might crank-up the PWM until the fan comes-on.

True, I should have mentioned that I assume that there is no feedback. If there is a tacho-signal, you have to fake that. But that's not as easy as reading and generating pwm.

lg, couka

Looks like i might be better off using that god awful asus software to control fans. As far as i remeber, it does support spinning the fans down (fan xpert2). But i really don't want to use that, but rather have a hardware solution, independent of OS/software.

You have another possibility - ditch the motherboard fan control entirely and just build your own, temperature-controlled PWM fan controller.

You say "fans" in your original post, do you mean case fans or the CPU fan? Case fans won't usually be a problem but as others have pointed out if the motherboard / operating system thinks the CPU fan has stopped then it might shut down your system. You BIOS may be able to shut off the fan speed detection so it (and/or your operating system) has no idea whether the fan is running or not.

Ralph_S_Bacon: if the motherboard / operating system thinks the CPU fan has stopped then it might shut down your system.

I doubt that. The CPU has temperature sensors and shuts itself down, when it becomes to hot. Shutting down the system because a fan fails wouldn't make much sense.

lg, couka

couka: I doubt that. The CPU has temperature sensors and shuts itself down, when it becomes to hot. Shutting down the system because a fan fails wouldn't make much sense.

I'm afraid that's not the case. On many motherboards, unless you have specifically disabled or configured the feature in the BIOS, PCs will shut themselves down if they think the CPU fan has failed (based on the SENSE output of the fan). The options were something like "ignore", "throttle", "alarm" etc.

I base this on many years of building PCs, admittedly back in the dark ages when electricity had barely been invented and a Pentium 4 (single core, of course, not that the term 'core' was even used then) was the home-equivalent of a Cray SuperComputer. :smiling_imp:

Today they might just send you an email instead and switch on your kettle for you via IoT to have a cup of tea whilst you fix things...

Ralph_S_Bacon:
You have another possibility - ditch the motherboard fan control entirely and just build your own, temperature-controlled PWM fan controller.

You say “fans” in your original post, do you mean case fans or the CPU fan? Case fans won’t usually be a problem but as others have pointed out if the motherboard / operating system thinks the CPU fan has stopped then it might shut down your system. You BIOS may be able to shut off the fan speed detection so it (and/or your operating system) has no idea whether the fan is running or not.

I only have two fans on my Noctua u12p, no other fans in the system (well apart from PSU).

I’m sure it would work just fine when at 0rpm, otherwise they would not implement that feature onto fanxpert2.

Looks like arctic already has something like this

Too bad they don’t sell the fans separately :slight_smile:

So, is it possible to do this via arduino ?

So, is it possible to do this via arduino ?

So you want to control the two CASE fans not the CPU fan? Correct?

Then YES it is very possible. And to simplify the whole thing forget the motherboard temperature control and just create your own Arduino-based temperature-controlled PWM fan controller. Many noobs do this project, one way or another. Even I have two PWM fans controlled in this way in my computer cupboard.

  • You need to measure the temperature (see my YouTube video #28 on using the OneWire DS18B20 temperature controller) which is very easy to use for a noob.
  • You need to control the fan(s) with PWM (see my YouTube videos #14 & #15 - they go on a bit but contain the information you need, especially #15). You will see my fans in the computer cupboard in this video!
  • Put the two things together (ask here if you get stuck with this last step) so the temperature controls the fan speed.

I look forward to your next post when you have successfully completed steps 1 & 2, very straightforward. Or if you get stuck in those steps.

URLs for my videos in the footer of this post. Subscribe too if you find them useful! What a great project for a sunny May weekend.

Ralph_S_Bacon: So you want to control the two CASE fans not the CPU fan? Correct?

Then YES it is very possible. And to simplify the whole thing forget the motherboard temperature control and just create your own Arduino-based temperature-controlled PWM fan controller. Many noobs do this project, one way or another. Even I have two PWM fans controlled in this way in my computer cupboard.

  • You need to measure the temperature (see my YouTube video #28 on using the OneWire DS18B20 temperature controller) which is very easy to use for a noob.
  • You need to control the fan(s) with PWM (see my YouTube videos #14 & #15 - they go on a bit but contain the information you need, especially #15). You will see my fans in the computer cupboard in this video!
  • Put the two things together (ask here if you get stuck with this last step) so the temperature controls the fan speed.

I look forward to your next post when you have successfully completed steps 1 & 2, very straightforward. Or if you get stuck in those steps.

URLs for my videos in the footer of this post. Subscribe too if you find them useful! What a great project for a sunny May weekend.

Those are case fun, but used in a CPU heatsink.

I don't want to make a fan controller with arduino, what i want is to emulate the functionality, that arctic offers with said cooler. So semi passive operation until a certain pwm value.

So the idea is, that arduino reads the pwm values, that motherboard provides and either forwards them to the fan after a certain threshold (like 40%) or ignores them (0% pwm to the fan).

SO the question is really, can arduino read pwm values, that motherboard sends ? Obviously fan control on its own works.