The problem I have is that when when I try to read a 4-pin fans RPM speed it only works when I am not trying to control it via PWM. Otherwise it gives a false (much higher) speed.
I have been searching for an answer to my problem, but I haven't found anyone with the same issue that has been answered.
I have been making a fan controller using an Arduino Nano, an Artic F12 PWM 4-pin fan as well as a 1-wire temperatue sensor and a HD44780 LCD for a display.
I am using PWM library to run the fans at 25khz and that seems to work great. - http://forum.arduino.cc/index.php?topic=117425.0
I am using a 10k pull up to read the RPM and when the PWM is not being used then it reads correctly at 1250rpm, but when the PWM line is used the value goes crazy.
Many thanks for any advice you can give,