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Posted

i feel so dumb :help:

 

LOL. They are quite cool things but I wouldn't pretend they have massive applications in our field. They are an expensive alternative to a fusebox and relay board. Think of them as a computer-controlled set of relays. You buy them for a number of channels (however many suit your needs - how many circuits do you want to switch). All the on/off logic is defined in computer configuration - there is no hard wiring config. You have a set of input wires, and a set of outputs. In the simplest configuration, you would program the unit so that when an input wire changes state, the corresponding output wire changes state also. So a simple on/off toggle.

 

Now obviously that's very low-end and if you was just going to set up 3 circuits that all do that, there's little need for a PDM. But the power comes when you want to define logic based on multiple inputs. For example, a fog light output that will only toggle if the dip beams are on. Or a wash/wipe cycle that will turn on the motor circuit for the wipers as well as the pump. Or a fuel pump feed that will only run the pump for a limited period of time without seeing an engine crank signal.

 

The other benefits of the PDM is it's solid state, so very resistant to harsh environments, and there are no fuses to blow - it monitors voltage, current and temperature and will automatically reset circuits as needed (it can even retry them a number of times before permanently 'tripping' and disabling the circuit). Main uses are in motorsport really, but if you were feeling flush it would make wiring up a kit a piece of piss, provided you were savvy with a laptop and basic logic principles.

 

I made a video for another forum which doesn't really explain much but if it interests you :-

  • 4 weeks later...
Posted

the way i was told was that the fog light should not flicker when high and low beam was used ,

ie the change over

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