Comair Rotron PWM Control Circuit

Electromechanical Fans, Thermal Management
, , ,
1

Hi,

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.

image
image698×451 15.3 KB

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.

Kind regards,
Todd Daynes

2

Greetings,

The datasheet would appear to call for open-collector interfaces on both signals, as is common due to flexibility in regard to logic levels that technique affords. Such devices generally provide their own input pull-ups, so an external one (R155) should not be necessary, and it would be prudent to chose Q13 so as to tolerate being pulled up to the fan supply voltage.