Regulator of 4-wire PWM fans

The article was published in April 2018 in Czech magazine Praktická elektronika - Amatérské Radio. It is written in Slovak language.

The article describes construction of regulator for a 4-wire PWM fans. I have built it because I needed to cool my laptop which was overheating under heavy CPU load.

When switched on the first time the regulator performs calibration of RPM indication. It measures maximal and minimal RPM and uses this range information for indicating RPM by LED bar. This information is saved to the EEPROM of the MCU so the calibration don't have to be performed the next time when the regulrator is switched on. Calibration can also be forced by keeping the button pressed when switching on the regulator.

The regulator has four modes for indicating approximate RPM of the fan. User can cycle through these modes by pressing the button.

Auto-off means that when RPM does not change for a few seconds the green LEDs are switched off and only the first green LED is on with low brightness. LEDs are switched back on when a significant change of the RPM occures. Significant change is change in the RPM that would lead to change of the LED's states in non-auto-off modes.

Archive with the C source codes and Atmel Studio project files can be downloaded from the magazine web page The source codes can also be found in my GitHub repository.

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