Tach connection may damage 24V fans.

[ilikecake]

Your EBB SB2209 CAN (RP2040) design allows for selecting 5, 12, or 24V for the 4-wire fan. When 24V is selected this pulls up the tach pin to ~24V.

With the 1K resistor on that line, that will result in a current flow of ~24mA through the fan when the tach signal is pulled low.

All of the datasheets for 24V fans that I have seen have suggested limiting the current and voltage on the tach line so that no more than 2-5mA go through the fan. Has this been tested? Can you change the signal conditioning on the tach signal to a larger pull-up resistor and switch the pull up voltage to 5V?

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[Bazeone]

This also happens on the EBB SB2209 CAN (STM32) version. I had a GDSTIME 4010 24V 4 wire fan connected to 4WFan port and the tach was not working. Switching the 4WFan port to 5V and splitting the wires between Fan1 for power at 24V, PWM and Tach on the 4WFan port at 5V allow this fan to work with correct tach readings.