Welcome, Guest
Username: Password: Secret Key Remember me

TOPIC: Controlling 4 pin PWM PC Case Fans with an MCU

Controlling 4 pin PWM PC Case Fans with an MCU 3 years 4 months ago #17743

  • hop
  • hop's Avatar
  • Offline
  • Platinum Boarder
  • Posts: 526
  • Thanks received: 46
I am revising my project I started many moons ago, and now that PWM PC case fans are available, and so is the support technology on the motherboard, it's time to go after this again. I want to build a mosquitto (MQTT) node in my PC that reports temps and controls fan speeds. Autonomously of course, but also under server supervision. The PWM fans I picked have LED ports (but no LED's) that I can attach WS2812 led's to and can control with the same attached fan controller.

So all I need to know now is what frequency the PWM is expected to be by the internal fan controller, the signal voltage level, and how the tach line reports the RPM's, and what voltage that signal is also. I have a working model attached to a PWM supported motherboard, so it is just a matter of attaching my scope and getting some samples.

I am not looking to do any fancy touch screen or control interfaces just yet, but if I do, they can be MQTT also and feed and be fed the data from the modified fans.

I figure I need one ESP8266 12e and a pro mini for each fan/light location. And a temp sensor for each location also.

Anyone have any data on the latest PWM PC fans (4 pin - 12vdc, gnd, tach, control and not in that order), I would appreciate it.

The analog fan (200mm Antec) has three speeds and I can just switch it's wiring electronically.

This will be fun! More when I know it. :D

Controlling 4 pin PWM PC Case Fans with an MCU 3 years 4 months ago #17744

  • be80be
  • be80be's Avatar
  • Offline
  • Senior Boarder
  • Posts: 79
  • Thanks received: 90
Just for you www.analog.com/library/analogDialogue/ar.../38-02/fan_speed.pdf

Here a link to the controller for computer fans www.onsemi.com/pub_link/Collateral/ADT7460-D.PDF
Page 29 it looks like 35.6 hz pwm for full speed.
Last Edit: 3 years 4 months ago by be80be.
The following user(s) said Thank You: hop

Controlling 4 pin PWM PC Case Fans with an MCU 3 years 4 months ago #17746

  • hop
  • hop's Avatar
  • Offline
  • Platinum Boarder
  • Posts: 526
  • Thanks received: 46
be80be wrote:
Just for you www.analog.com/library/analogDialogue/ar.../38-02/fan_speed.pdf

Here a link to the controller for computer fans www.onsemi.com/pub_link/Collateral/ADT7460-D.PDF
Page 29 it looks like 35.6 hz pwm for full speed.

Thank you! Just to clarify though, it's not the pwm frame rate that controls the speed, it's the duty cycle. So although default of 35.6 hz, it's not just for full speed. I will have to try the various frame rates until I find what the controller inside the PWM fan is expecting. I'll bet though that it is 35.6 hz. A simple scope sample of an existing PWM fan system will tell me that frame rate though. I just haven't got around to it yet. Going after that Sunday. NEAT CHIP!!! I wonder if this is what is on the newer motherboards.

Controlling 4 pin PWM PC Case Fans with an MCU 3 years 4 months ago #17747

  • hop
  • hop's Avatar
  • Offline
  • Platinum Boarder
  • Posts: 526
  • Thanks received: 46
Noticed that the temp sensors for this incredible chip are analog. Interesting that they are not one-wire. I will have to run it in manual mode because I am using one-wire digital temp sensors. Then, it becomes questionable as to why I cannot just do the PWM and tach sensing on a PIC, ATMEGA328P, or an ESP8266-12e directly.

Controlling 4 pin PWM PC Case Fans with an MCU 3 years 4 months ago #17748

  • be80be
  • be80be's Avatar
  • Offline
  • Senior Boarder
  • Posts: 79
  • Thanks received: 90
This show's more about the PWM and how not to over drive it www.formfactors.org/developer%5Cspecs%5C4_Wire_PWM_Spec.pdf

Controlling 4 pin PWM PC Case Fans with an MCU 3 years 4 months ago #17749

  • hop
  • hop's Avatar
  • Offline
  • Platinum Boarder
  • Posts: 526
  • Thanks received: 46
be80be wrote:
This show's more about the PWM and how not to over drive it www.formfactors.org/developer%5Cspecs%5C4_Wire_PWM_Spec.pdf

Wow interesting! Thanks for the PDF Spec file by the way! That's in my OneNote right now! VERY USEFUL!!! Weird that once again in the spec that 25 khz frame rate is considered the standard yet that chip uses something else as a default. Weirder still is that the tach signal is pulled up to 12v yet the PWM is 5v standard. Adjusting that 12v tach signal to 3.3 or 5v should be easy enough though. I absolutely LOVE this cooling fan control design though! The power for the fans is direct, and only the control signals need to come from the controller. That saves a lot of mosfet/transistor implementations and worries about current draw from the controller. It's about time!

Thank you sir for the info and replies!
Time to create page: 0.245 seconds