Electrical Experts Needed

"bobbe17" (rob-runte) 03/13/2016 at 18:56 • Filed to: None

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I started in on my project to hardwire my dashcam into the M3 this weekend. After stripping much of the interior and getting it all wired in, I was extremely excited when I turned the ignition switch, and it worked! Then, I turned on the radio and it was filled with static. Turned off the ignition, and the static went away.

So the details are that I wanted to do this project the right way. No soldering onto existing connections and no splicing wires. I bought an add a fuse to tap into the circuit for the garage door (on only with ignition) and ran the wires along the A-pillar and behind the headliner.

The issue comes from the fact that the dashcam runs off of 5V which meant that I needed to install a 12V to 5V step down. I believe that it is the step down box itself that is causing the interference through the air. For some trouble shooting I brought in a standalone radio and it was interfered with as well.

So my questions are- Is there some sort of shielding that I can wrap it in to keep the interference from getting out? Could it be a flaw with this specific unit, or would another likely do the same thing? Is there any further troubleshooting I can do? The unit I bought is !!!error: Indecipherable SUB-paragraph formatting!!! .

DrJohannVegas > bobbe17 03/13/2016 at 19:19

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I hate to be so blunt about this, but: This looks like a super-cheap switching power supply. All of the interference is from the high-frequency switching going on inside which is doing the voltage dividing from 12v to 5v. At a price that low, they aren’t going to invest in RF shielding, I guarantee. You might be able to bodge together some DIY shielding, but that may be more work than you’re looking to do.

Edit: I guess option 2 is to relocate the step-down supply somewhere further away from the radio and antenna wiring, then run the (probably) cleaner 5v supply by itself up to where the dashcam is.

Jake, Yes, wearing khakis > bobbe17 03/13/2016 at 19:21

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Does the original lighter socket power adapter that came with the dashcam cause interference when it’s powering said dashcam?

4muddyfeet - bare knuckle with an EZ30 > DrJohannVegas 03/13/2016 at 19:33

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Aluminium turkey foil is a fairly low cost DIY solution. Not perfect, but an option at least!

DrJohannVegas > 4muddyfeet - bare knuckle with an EZ30 03/13/2016 at 19:38

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Good enough for a first try, but Al doesn’t really shield all that well. One nice thing about the rise of the maker community in its modern form is that copper RF shielding tape is pretty cheap/easily available.

4muddyfeet - bare knuckle with an EZ30 > DrJohannVegas 03/13/2016 at 19:48

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I’m not sure you know what you’re talking about. Alu foil works for everything, even alien transmissions.

The Snowman > Jake, Yes, wearing khakis 03/13/2016 at 19:59

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Exactly my thought wire that sob in permanent.

DrJohannVegas > 4muddyfeet - bare knuckle with an EZ30 03/13/2016 at 20:19

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Shhhhhh. They know.

4muddyfeet - bare knuckle with an EZ30 > DrJohannVegas 03/13/2016 at 20:21

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Not fucking likely

bobbe17 > DrJohannVegas 03/13/2016 at 20:24

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No offense taken. I have just enough electrical knowledge to make myself dangerous. Thanks for the explanation, that explains what’s actually going on. So is the difference between the piece of crap I bought and a normal cigarette lighter adapter just shielding or is it better components?

bobbe17 > 4muddyfeet - bare knuckle with an EZ30 03/13/2016 at 20:25

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I definitely thought of that too but would be disappointed in myself for getting sloppy.

bobbe17 > The Snowman 03/13/2016 at 20:27

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I considered that as well, but I have two cars that I move the camera back and forth from so I’d like to leave it intact until I get one done. Might go out and by one though, I’m sure it’ll be better quality than what I have now.

DrJohannVegas > 4muddyfeet - bare knuckle with an EZ30 03/13/2016 at 20:32

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That escalated, but probably not quickly.

DrJohannVegas > bobbe17 03/13/2016 at 20:36

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Probably a little more shielding (even a crummy tin/steel shield will help), maybe slightly less noisy circuit design and components, and also the distance. Every little bit helps.

Also, being dangerous is the first step on the way to being less dangerous! (It’s a corollary of: “Sucking at something is the first step to being sorta good at something.”)