MoTeC Global Forum

Hello Everyone,

I have researched but cannot seem to understand the behavior of the PWM AUX Table on a M400 ECU.
I am trying to drive a PWM controller using Function 3 on AUX 1 with RPM and GEAR as axis.

I have set the ECU to do high pull up, min duty 0, max duty 100.
My table goes from 0 to 100 in duty cycle, but I noticed my pump (attached to controller) is off from 0 to 50 and then turns on to full speed from 50 to 100.
I attached an oscilloscope and noticed that there is no PWM, it's behaves like a switch (over 50% on, under 50% off)

I got my controller to work properly using the "test output" function in ECU manager.

What am I missing, I saw some forum post about using a pull up resistor and using different AUX outputs.
A forum post mentions to switch the polarity to 0 (switch to ground and use a pull up resistor from a 12v source), is that the correct way ? I am used to micro controller Pwm signal of 5v square wave.

Thank you!

What are the Parameters for Aux 1 - Aux Table? You want to make sure PWM/Switched is 0 (sounds like you might have this set to 1).

Output Mode and Polarity will depend on your wiring -- you can usually change this to get it to work however you've wired it. Did you try Output Mode = 2 (so it switches both low and high)?

Also, the Frequency must be at least 15 hz (try 100 hz -- your PWM controller might have a range it works with).

Finally the Minimum and Maximum Duty Cycle need to be set appropriately (min = 0, max = 100) is a good place to start -- your PWM controller might have some limits that need to be observed.