I have a customer usign Comair DC fan PN 17001130A. I am interfacing to the fan’s PWM control wire (yellow) through J27 pin 4 in the schematic below. PWM signal PWM_SYS_FAN_OUT1 (3.3V logic from an MCU) will run at 1Khz with and be controlled so the fan yellow wire has a 15% to 40% duty cycle to control fan speed. Q13 inverts PWM_SYS_FAN_OUT1 and drives yellow wire high at 5V with 10.2K source impedance and low at close to 0V with 2ohm of source impedance.
Signal GPI_TIMER_SYS_FAN_TAC_IN_1 goes to an MCU with 3.3V I/O. R154 pulls the open collector (to be confirmed) signal from the fan to create a 3.3V logic level high for the MCU.
Please confirm that this PWM and tach circuit is compatable with this fan.
A schematic of the PWM input and Tach output signals on the fan side woudl also be nice to have.