I'm slowly working my way through setting up my PDM.
I have one stumbling block at present. My ECU (Emerald K6+) is capable of controlling my water/meth system using a 2D lookup table (using boost and revs). This outputs a PWM low sided signal.
I could use a Solid State Relay to control the water/meth injection but would rather use the PDM. Can I use a PDM input to read the PWM signal and then use this to switch an output to my water/meth injection? The PWM Input is 'only' an on/off signal so I'm guessing this would be OK but, as the water/meth system needs to be 100% reliable, I'd rather make sure this is right! Thanks. Wyn.
@Wyn Edwards Did you get the water/methanol sorted? I have a K6.
Thanks George. I guessed there'd be a problem.
Unfortunately, the CAN output from my ECU is limited and not configurable, so I will have to go down the SSR route.
I suppose I could map the duty cycle to one of boost, revs or injector pulse width (which are part of the CAN stream) and have a function that uses one of the others to control on/off.
Hi Wyn, The PDM inputs can not read the frequency of an input signal. It is also not a good idea to send a PWM signal to the PDM input to directly control an output, as the PDM input sampling time will likely not be high enough to achieve smooth operation. You depending on the PWM frequency, you will see a lot of pulse width jitter on the output.
A better way to do this, would be to send a CAN message to the PDM from the ECU with the required frequency, and then drive the output using that value.
Alternatively, you can use the PDM output to feed a SSR, and use the ECU to trigger the SSR.