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A question for your engineers about using relays to drive led controllers

Gnome

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I have a question for your engineers about using relays to drive your controllers. Looking at your fitting instructions for the DRL boards for the mustang as an example, it indicates you take power from the existing DRL and parking light wires (and turn signal if you have the RGBWA option).

All pretty straight forward, but I have been talking to some people that are planning to use a relay in between, with the idea in mind that if there is a problem with the controller it will protect the cars original electrics.

Based on my experience of problems created when you power a relay from something that was never designed to drive an inductive load, my question is can this create a problem all of its own?
If you use the power going to the original DRL for example to power a relay to run your controller, when it switches off you get a back EMF that can be a few hundred volts, normally this is not an issue on older cars with mechanical switching or the lights , but if the power feed for the original DRL is switched electronically by one of the car's modules, which I imagine they are, then this spike may cause all sorts or intermittent problems, or even in the worst case damage the cars electrics eventually. This is not something that is well known, but there are relays around with built in diodes specifically for this problem.

I would be interested to hear what your engineers have to say about this, and it even may explain why some people have strange issues and most others don't.
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Diode Dynamics

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The DRL hot wire in the headlamp is directly linked to the battery, so there is no problem in using it for the main power supply with the boards. And as such, if you want to replace it with a relay, there would be no problem.

The parking wire however (purple/white headlamp wire) is a signal, not power, so it would not be wise to drive a relay coil with it. Yes, relays can have flyback diodes built in, but just in terms of driving a relay, aside from flyback spikes, I would not recommend it.

Thanks!
 
 




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