PDM parallel output method

Discussion and support for MoTeC Power Distribution Modules

PDM parallel output method

Postby SXD on Mon May 24, 2021 9:57 pm

I'm setting up a PDM15 for my race car, and I plan to use three high current channels to run my electric power steering pump - mainly so I can keep track of total electrical load since I run close to the limits of my alternator.

Is there a preferred method for setting up parallel outputs?
The manual seems to suggest they can be paralleled as long as they have the same control conditions, and are of the same type.
Can I name the parallel channels the same and have them all reported as one, or is there a way to add them together into one channel for current reporting?


thanks!
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Re: PDM parallel output method

Postby David Ferguson on Tue May 25, 2021 4:35 am

The channels have to have a unique name, but you can use a function to create the condition to turn them all on/off at the same time.

As far as summing the currents / loads, you can't do this in the PDM, however you may be able to do this in a MoTeC dash (depends on model), but certainly in I2 Pro.
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Re: PDM parallel output method

Postby SXD on Tue May 25, 2021 8:48 am

thanks :)
It's easy enough to add them together later, but would be very convenient if channels could be combined at the PDM from a data point of view.
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Re: PDM parallel output method

Postby SDean on Tue May 25, 2021 11:10 am

It is better to have each of the channels logged separately and then combine them in i2 as this allows for differences in the current draw on each output to be detected and rectified if needed.

To parallel outputs, I construct the control functionality as a function, and use that functions output as the switching channel for the output. When you wire the output, you need to ensure that each of the wires that connect the load to the PDM are as close as possible to being the same length, otherwise it is possible for one of the outputs to have more load compared to the others.
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Re: PDM parallel output method

Postby SXD on Tue May 25, 2021 6:54 pm

Thanks Stephen,

The outputs are combined quite close to the PDM so there should be no problem with load sharing.
Using three outputs there will be plenty of headroom too.

The pump has its own control signal so these outputs will be "always on", but I'll have a look at the option for control functions for other channels (multiple fuel pumps etc)
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