Help with PWM
Posted: Thu Oct 02, 2014 3:59 am
I need to drive the fan on my E46 BMW and I believe it uses a PWM value. I found the following documentation from someone who was building his own replacement controller: The fan signal trigger from the DME sends a 95% duty 100Hz PWM signal whenever the key is on and Fan Request is OFF. The DME's signal trigger is inverted. 90% duty signal from DME is 10% fan motor power while 10% duty signal from DME is 90% fan motor power.
Using the fan test function in Launch X-431, the following was observed:
Commanded Duty / Voltage after RC filter / Fan Speed
30% / 3.0V / LOW
60% / 1.7V / MEDIUM
90% / 0.4V / HIGH
OFF / 4.2V / OFF
Key off / 0V / OFF
What would the proper settings be to use this on PWM1 channel? I plan to write a script that turns on the fan if the speed is below 25MPH or the temp gets above 200 degrees. I already have a temp sensor installed.
Using the fan test function in Launch X-431, the following was observed:
Commanded Duty / Voltage after RC filter / Fan Speed
30% / 3.0V / LOW
60% / 1.7V / MEDIUM
90% / 0.4V / HIGH
OFF / 4.2V / OFF
Key off / 0V / OFF
What would the proper settings be to use this on PWM1 channel? I plan to write a script that turns on the fan if the speed is below 25MPH or the temp gets above 200 degrees. I already have a temp sensor installed.