7 ms·

Built a cheap DIY fan controller because my motherboard never had working PWM

77 points by bobsterlobster 6mo ago

bobsterlobster 6mo ago
MSI shipped a genuinely good motherboard and forgot to wire one chip, so PWM doesn't work. Instead of tossing the board or living with the noise, I decided to make lemonade. An Arduino Nano generates the 25kHz PWM signal, and a companion Windows application reads CPU temp and sends the duty cycle over serial. The Arduino firmware is open source (MIT).
- gzread 6mo ago
  What if Windows crashes? It's better to attach a thermal sensor to the heatsink, I think.
  - johndough 6mo ago
    Just send a heartbeat every few milliseconds and set fan speed to 100% if it died. Bonus: You get an audible indicator that the system crashed.
  - crote 6mo ago
    Well, what if? We don't live in the AMD Athlon era[0] anymore. Modern CPUs are designed to boost until they hit a thermal limit, improper cooling is just going to result in a lower clock speed. [0]: https://youtu.be/UoXRHexGIok?t=55 https://youtu.be/UoXRHexGIok?t=55
    - joe_mamba 6mo ago
      Damn, that video took me waaay back.
    - bobsterlobster 6mo ago
      What a blast from the past. I still remember seeing it for the first time on my Socket A Athlon 1900+ pc.
  - bobsterlobster 6mo ago
    If windows crashes, then the audio generation crashes, so the fan will start to operate without PWM. Should default to 100%. At least that's how the PWM fans I have behave when the PWM signal suddenly disappears.
- haktan 6mo ago
  Could you use an audio out port for creating the signal and ditch the Arduino?
  - magicalhippo 6mo ago
    That might work for the PWM signal, however you'd still need some electronics as the fan has internal pull-up to 5V and expects it to be pulled low by the PWM signal. But a small circuit with a Schmitt-trigger inverter IC and some resistors and capacitors might do the trick, for example.
  - bobsterlobster 6mo ago
    Interesting idea, I'll look into it.
realaccfromPL 6mo ago
This looks really good! I am trying to do the same thing for cooling 11th gen Intel laptop motherboards with micro RP2050 board but came to the conclusion that I should just do it with ESP32 as mine has some limitations. Would you mind sharing more technical review of what you created?
- zeroflow 6mo ago
  RP2050 would work, as it also has the necessary built-in peripherals. ESP32 would add wifi and better ESPHome support. I suggest you stay away from the ESP8266, as it needs to do PWM in software and struggles with the 25kHz output frequency. From my experience: ESP32/RP2040 work without additional circuitry which works with most fans, but for protection, you want to add level shifters. Not all fans pull up the PWM pin to 3.3V, the spec allows for 5V. Shameless plug, hopefully this is allowed here. I built something like that, that allows fan control via WiFi. First I built it only for myself, but since the spare boards from PCBA quickly sold, I decided to keep it stocked. Short gist: 12V Input, ESP32S2, ESPHome-based. Has 4 PWM-fan outputs, onboard temperature & humidity sensor and Qwiic expansion port. The ESPHome code & schematic is on Github: https://github.com/zeroflow/wifi-fancontroller https://github.com/zeroflow/wifi-fancontroller If you want one, it's available on Elecrow for $35,99: https://www.elecrow.com/wifi-fancontroller1.html https://www.elecrow.com/wifi-fancontroller1.html If you want to build it by yourself, the schematic is in the hardware folder. And if you don't want to use ESPHome - there is no firmware lock, you find the pin assignment on the product page and can write your own firmware if you so desire.
  - realaccfromPL 6mo ago
    Really appreciate your reply!!
rurban 6mo ago
I've built 4 different fan controllers for my companies' embedded board so far. We work in very hot greenhouses, so fans (and peltiers) are essential. And proper thermal sensors. I check 4 different ones. Esp. needed is also a humidity sensor, because we don't want it to cool down below the dew point. It's PWM, controlled via mraa. mraa_pwm_write()
- elevation 6mo ago
  > peltiers) are essential Peltiers have a lifetime measured in cycles, cycling from active (maximum delta Temp) to inactive (both sides ambient). After 1-2k cycles, Peltiers gradually lose efficiency and transition from a heat pump to a hot plate. For this reason I've avoided them in my own permanent installations. Have you encountered this?
  - rurban 6mo ago
    Yes, peltiers only help a bit. And don't last long. Most of the heavy work is done by huge fans.
- uticus 6mo ago
  > peltiers First time I've come across this technology. A solid-state heat pump? Magic! https://en.wikipedia.org/wiki/Thermoelectric_heat_pump https://en.wikipedia.org/wiki/Thermoelectric_heat_pump
venzaspa 6mo ago
Ironic, the day after the launch of Artemis II that people are using microcontrollers far more powerful than the original Apollo 11 navigation computer to control a single fan in their PCs now.
- dv_dt 6mo ago
  One could go farther and complain that it's a waste of a microcontroller at all to control a fan when an analog circuit for fan speed vs temperature would work fine.
  - pjc50 6mo ago
    Nah, it's a much lower part count and much simpler to put a microcontroller in. If you're concerned about cost cheaper parts are available.
    - MisterTea 6mo ago
      Yup. You could use a quad opamp to build a PWM controller with closed loop control but then you need all the passives to setup the oscillator and so on. I went through this years ago making a fan driver for my vehicles HVAC blower. The analog setup was fun to make but you use more board space, higher BOM count, and really, higher BOM cost vs a micro-controller.
      - fragmede 6mo ago
        It's crazy how far technology has advanced. A μc with RAM and a bunch of input and output ports and some code is cheaper today than a pile of analog components.
  - adrian_b 6mo ago
    True, a very simple analog circuit would be enough. However the bane of analog circuits was that they age, so a control circuit that works perfectly today will drift and no longer work as intended after some years. The second problem is that analog circuits need adjustments to set them at the exact desired parameters. Adjustments can be done either by using an adjustable element in the circuit, e.g. an adjustable resistor or capacitor or inductor, or by measuring many resistors and/or capacitors and/or inductors and selecting the ones with the right values to be used by your device. Redoing periodically the adjustments also solves the aging problem. However, both the initial adjustment and any periodic readjustments need a lot of work, so they are no longer acceptable in the industry. When doing something for yourself, you may make an analog controller and the initial adjustment would not be a problem, but even in this case it would be annoying to keep track and remember something like having to readjust a fan controller every 6 months, to be sure that it still works as intended.
rasz 6mo ago
>This board has a Fintek F71878AD, a perfectly capable Super IO controller that can read temperatures, control fan PWM, and monitor fan speeds, but MSI just didn't connect it to the board. is not true. There is a diagram available for this mobo and U32 (F71889AD) is connected over LPC (modern serial ISA version). Its a full Super IO and it cant be _not connected_ as it also provides keyboard/mouse, serial and printer ports. The problem must lie elsewhere, most likely bad BIOS. >Here's what I knew: > Windows can read CPU temperature directly from the CPU's internal thermal diode, completely bypassing the useless Super IO chip. why not read temperature directly from Fintek using HwInfo? https://www.hwinfo.com/forum/threads/faulty-sensor-readings-on-msi-990fxa-gd80.361/ https://www.hwinfo.com/forum/threads/faulty-sensor-readings-... and yes it also works on 970 https://forum-en.msi.com/index.php?threads/msi-970-cpu-temps-with-hwinfo.254381/post-1462006 https://forum-en.msi.com/index.php?threads/msi-970-cpu-temps... not to mention MSI Command Center can read those sensors AND set FAN speeds/curves, and most likely also SpeedFan. > asked LLMs LLM failed this person :(
- nottorp 6mo ago
  ... but he had fun doing it!
  - deleted 6mo ago
    [deleted]
- wildzzz 6mo ago
  Yeah I was going to say that the presence of a PS/2 port almost certainly means it has a SuperI/O chip wired up. You wouldn't be able to shutdown the PC without the LPC bus talking to the SuperI/O. MSI just didn't write code to talk to the fan controller or just didn't bother with displaying it in the BIOS config page.
  - rasz 6mo ago
    There are multiple pictures of msi 970 master bios displaying temps and fans just fine so it did work at some point in time. Author either updated to some poorly validated bugfix only/beta bios, or maybe wrong bios for the board.
Chepko932 6mo ago
Glad you shared this. I ran into something similar when I tried using a Pico W as a USB HID device, hardware was up to the task, but the firmware just wouldn’t let me get where I wanted.. Using Arduino and serial is a smart way to go here. Still, it’s worth remembering: the Pico W has built-in WiFi, so you don’t have to lean on serial if you don’t want to. You could have your temp-reading app send control signals over HTTP instead. No need to tie up the USB port, and the connection isn’t killed if someone yanks the cable. And yes, big agreement on the watchdog or failsafe. Any fan controller that doesn’t ramp up to 100% if it loses connection is just waiting for trouble. Fire risk is real.

MSI shipped a genuinely good motherboard and forgot to wire one chip, so PWM doesn't work. Instead of tossing the board or living with the noise, I decided to make lemonade. An Arduino Nano generates the 25kHz PWM signal, and a companion Windows application reads CPU temp and sends the duty cycle over serial. The Arduino firmware is open source (MIT).

gzread 6mo ago
What if Windows crashes? It's better to attach a thermal sensor to the heatsink, I think.
- johndough 6mo ago
  Just send a heartbeat every few milliseconds and set fan speed to 100% if it died. Bonus: You get an audible indicator that the system crashed.
- crote 6mo ago
  Well, what if? We don't live in the AMD Athlon era[0] anymore. Modern CPUs are designed to boost until they hit a thermal limit, improper cooling is just going to result in a lower clock speed. [0]: https://youtu.be/UoXRHexGIok?t=55 https://youtu.be/UoXRHexGIok?t=55
  - joe_mamba 6mo ago
    Damn, that video took me waaay back.
  - bobsterlobster 6mo ago
    What a blast from the past. I still remember seeing it for the first time on my Socket A Athlon 1900+ pc.
- bobsterlobster 6mo ago
  If windows crashes, then the audio generation crashes, so the fan will start to operate without PWM. Should default to 100%. At least that's how the PWM fans I have behave when the PWM signal suddenly disappears.
haktan 6mo ago
Could you use an audio out port for creating the signal and ditch the Arduino?
- magicalhippo 6mo ago
  That might work for the PWM signal, however you'd still need some electronics as the fan has internal pull-up to 5V and expects it to be pulled low by the PWM signal. But a small circuit with a Schmitt-trigger inverter IC and some resistors and capacitors might do the trick, for example.
- bobsterlobster 6mo ago
  Interesting idea, I'll look into it.

realaccfromPL 6mo ago

This looks really good! I am trying to do the same thing for cooling 11th gen Intel laptop motherboards with micro RP2050 board but came to the conclusion that I should just do it with ESP32 as mine has some limitations. Would you mind sharing more technical review of what you created?

zeroflow 6mo ago
RP2050 would work, as it also has the necessary built-in peripherals. ESP32 would add wifi and better ESPHome support. I suggest you stay away from the ESP8266, as it needs to do PWM in software and struggles with the 25kHz output frequency. From my experience: ESP32/RP2040 work without additional circuitry which works with most fans, but for protection, you want to add level shifters. Not all fans pull up the PWM pin to 3.3V, the spec allows for 5V. Shameless plug, hopefully this is allowed here. I built something like that, that allows fan control via WiFi. First I built it only for myself, but since the spare boards from PCBA quickly sold, I decided to keep it stocked. Short gist: 12V Input, ESP32S2, ESPHome-based. Has 4 PWM-fan outputs, onboard temperature & humidity sensor and Qwiic expansion port. The ESPHome code & schematic is on Github: https://github.com/zeroflow/wifi-fancontroller https://github.com/zeroflow/wifi-fancontroller If you want one, it's available on Elecrow for $35,99: https://www.elecrow.com/wifi-fancontroller1.html https://www.elecrow.com/wifi-fancontroller1.html If you want to build it by yourself, the schematic is in the hardware folder. And if you don't want to use ESPHome - there is no firmware lock, you find the pin assignment on the product page and can write your own firmware if you so desire.
- realaccfromPL 6mo ago
  Really appreciate your reply!!

rurban 6mo ago

I've built 4 different fan controllers for my companies' embedded board so far. We work in very hot greenhouses, so fans (and peltiers) are essential. And proper thermal sensors. I check 4 different ones. Esp. needed is also a humidity sensor, because we don't want it to cool down below the dew point. It's PWM, controlled via mraa. mraa_pwm_write()

elevation 6mo ago
> peltiers) are essential Peltiers have a lifetime measured in cycles, cycling from active (maximum delta Temp) to inactive (both sides ambient). After 1-2k cycles, Peltiers gradually lose efficiency and transition from a heat pump to a hot plate. For this reason I've avoided them in my own permanent installations. Have you encountered this?
- rurban 6mo ago
  Yes, peltiers only help a bit. And don't last long. Most of the heavy work is done by huge fans.
uticus 6mo ago
> peltiers First time I've come across this technology. A solid-state heat pump? Magic! https://en.wikipedia.org/wiki/Thermoelectric_heat_pump https://en.wikipedia.org/wiki/Thermoelectric_heat_pump

venzaspa 6mo ago

Ironic, the day after the launch of Artemis II that people are using microcontrollers far more powerful than the original Apollo 11 navigation computer to control a single fan in their PCs now.

dv_dt 6mo ago
One could go farther and complain that it's a waste of a microcontroller at all to control a fan when an analog circuit for fan speed vs temperature would work fine.
- pjc50 6mo ago
  Nah, it's a much lower part count and much simpler to put a microcontroller in. If you're concerned about cost cheaper parts are available.
  - MisterTea 6mo ago
    Yup. You could use a quad opamp to build a PWM controller with closed loop control but then you need all the passives to setup the oscillator and so on. I went through this years ago making a fan driver for my vehicles HVAC blower. The analog setup was fun to make but you use more board space, higher BOM count, and really, higher BOM cost vs a micro-controller.
    - fragmede 6mo ago
      It's crazy how far technology has advanced. A μc with RAM and a bunch of input and output ports and some code is cheaper today than a pile of analog components.
- adrian_b 6mo ago
  True, a very simple analog circuit would be enough. However the bane of analog circuits was that they age, so a control circuit that works perfectly today will drift and no longer work as intended after some years. The second problem is that analog circuits need adjustments to set them at the exact desired parameters. Adjustments can be done either by using an adjustable element in the circuit, e.g. an adjustable resistor or capacitor or inductor, or by measuring many resistors and/or capacitors and/or inductors and selecting the ones with the right values to be used by your device. Redoing periodically the adjustments also solves the aging problem. However, both the initial adjustment and any periodic readjustments need a lot of work, so they are no longer acceptable in the industry. When doing something for yourself, you may make an analog controller and the initial adjustment would not be a problem, but even in this case it would be annoying to keep track and remember something like having to readjust a fan controller every 6 months, to be sure that it still works as intended.

rasz 6mo ago

>This board has a Fintek F71878AD, a perfectly capable Super IO controller that can read temperatures, control fan PWM, and monitor fan speeds, but MSI just didn't connect it to the board. is not true. There is a diagram available for this mobo and U32 (F71889AD) is connected over LPC (modern serial ISA version). Its a full Super IO and it cant be _not connected_ as it also provides keyboard/mouse, serial and printer ports. The problem must lie elsewhere, most likely bad BIOS. >Here's what I knew: > Windows can read CPU temperature directly from the CPU's internal thermal diode, completely bypassing the useless Super IO chip. why not read temperature directly from Fintek using HwInfo? https://www.hwinfo.com/forum/threads/faulty-sensor-readings-on-msi-990fxa-gd80.361/ https://www.hwinfo.com/forum/threads/faulty-sensor-readings-... and yes it also works on 970 https://forum-en.msi.com/index.php?threads/msi-970-cpu-temps-with-hwinfo.254381/post-1462006 https://forum-en.msi.com/index.php?threads/msi-970-cpu-temps... not to mention MSI Command Center can read those sensors AND set FAN speeds/curves, and most likely also SpeedFan. > asked LLMs LLM failed this person :(

nottorp 6mo ago
... but he had fun doing it!
- deleted 6mo ago
  [deleted]
wildzzz 6mo ago
Yeah I was going to say that the presence of a PS/2 port almost certainly means it has a SuperI/O chip wired up. You wouldn't be able to shutdown the PC without the LPC bus talking to the SuperI/O. MSI just didn't write code to talk to the fan controller or just didn't bother with displaying it in the BIOS config page.
- rasz 6mo ago
  There are multiple pictures of msi 970 master bios displaying temps and fans just fine so it did work at some point in time. Author either updated to some poorly validated bugfix only/beta bios, or maybe wrong bios for the board.

Chepko932 6mo ago

Glad you shared this. I ran into something similar when I tried using a Pico W as a USB HID device, hardware was up to the task, but the firmware just wouldn’t let me get where I wanted.. Using Arduino and serial is a smart way to go here. Still, it’s worth remembering: the Pico W has built-in WiFi, so you don’t have to lean on serial if you don’t want to. You could have your temp-reading app send control signals over HTTP instead. No need to tie up the USB port, and the connection isn’t killed if someone yanks the cable. And yes, big agreement on the watchdog or failsafe. Any fan controller that doesn’t ramp up to 100% if it loses connection is just waiting for trouble. Fire risk is real.