Automotive Relay Board

Totally stuck on acrylic projects today. :slight_smile:

As part of the electric car project I’ve posted in the Show and Tell thread, I’m now working through the controls in the dashboard and integrating them into the rest of the vehicle.

I have this relay board designed to help me keep things neat and tidy behind the dash because there is a lot going on. I just stuck a couple of the relays on there to help visualize, but you can see I’ve got nifty labels engraved right onto the board, and holes holes everywhere. Those are for wiring to route through and also for securing the wires and relays.

There’s an empty space next to the “dimmer” relay which is reserved for a 5 volt power supply to drive the coils on the relays.


Very cool!


I love functional projects!


Can you post this again so I can like it twice? One concern though is long term embrittlement of the acrylic. I would definitely anneal it and then try to mount it with some compliant washers to minimize the shock. Would be a drag if it broke while driving. Maybe even consider delrin instead.


That’s what I was thinking. Sure it is more expensive but I think it would be worth it for this application.


I was thinking about embrittlement as well because our heat here really takes its toll on any kind of plastic, but then realized I have some smoked gray acrylic out in the garage that’s been there at least 10-12 years and it’s in great condition except the masking drying out and peeling.

In fact last summer I took a chunk and bent it into a Z-shape to make a mounting bracket for a 600Amp contactor and another relay for the traction drive system and it worked wonderfully.

I’ll keep an eye on it though, and I think I might even install some hidden mechanical switches for redundancy to bypass this capacitive touch control I’m building just in case.


Is there such a thing? I thought it was brittle to start with and very stable over time. Other plastics go brittle due to UV but acrylic doesn’t absorb UV, so is pretty immune I think.

I do have some acrylic drawers that are about 40 years old that I store electronic components in, some of which are even older. They are mostly OK but one that has old metal can transistors in has crazed. I think they must release some fumes that affect it. Odd because they should be hermetically sealed.


I really don’t know. I was thinking of repeated mechanical stress and fatigue more then environmental change.

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Yes that probably does cause fatigue but that shape has no sharp corners, so should be quite resilient to cracking.

Well I haven’t built the first one yet and I’m thinking of version 2 because I can already see some other circuits I might want to add. LOL

I think the mounting holes look a bit close to the edge and I might want to upgrade to 1/4" material instead. That will make it real solid.


Maybe the extreme in-vehicle/in-garage/in-anything temps we have in the south serves to repeatedly anneal your acrylic :slight_smile: