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DIY LED COB DRL - Weekend Project


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Alternative title: the equally catchy "do it yourself light emitting diode chip on board daytime running lights".

So, I wanted some nice daytime running lights for the front of my '99 Arosa. I did NOT, however, want to shell out upwards of £60 for a kit, plus I like to bugger about with stuff like this.

I had a Google, did some reading, and [these] seemed to be just what I was looking for in a daytime running light. Low power consumption, aluminium body, insanely bright and reasonably priced. A year or so ago I used the older surface-mounted LED boards for this type of thing, my last project was running lights for my Suzuki Bandit, but these things are just in a different league in terms of material quality and brightness.

I'm pleased with the result but pictures don't do these lights justice:

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I started by experimenting with mounting the lights in/on the stock 'honeycomb' infills... that didn't go so well. On a completely unrelated note, if anyone has any unmolested Mk2 infills kicking around the garage then I'd like to buy you a beer...

Anyway. For the infills the lights are mounted on here, I used one of the finest sources of tough plastic you can find today: £2 chopping boards from Wilko's. (no, really). They're pretty flexible, have a texture that more or less matches plastic bumpers and they're pretty tough while being easy to work with with hand tools. With some flat black Plasti-Kote enamel paint on them they look pretty good, I think. When I get around to washing the rest of the car they might even match the plastic trim. I'll be replacing the fugly rusted screws asap.

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The LED lights came with some beastly 3M foam tape that would probably just pull the bumper off if you tried to pull them off hard enough, but I supplemented this by running a pair of zip ties around both ends of the lights. This also provides strain relief for the slightly wimpy wires that they come with. I cut them short and put on some insulated spade connectors behind the panels with some more manly wires. I would have just soldered the wires directly but I want these to be easily removable in case my MOT tester is having a bad day next time around.

Wiring

Parts list:

  • 2x 6.8" COB LED lights from here
  • 1x 12v 30A 4-pin relay, available here
  • 1x inline mini blade fuse holder & 15A fuse
  • 1x 12v illuminated rocker switch, SPST
  • Wire, lots of wire, some rated for >12w
  • Male and female spade connectors
  • 2x ring connectors for the battery terminal bolts
  • Metric d***ton of cable ties & shrink wrap tubing

I pulled three (blue) wires for the switch through the rubber grommet in the bulkhead that the main loom runs through, and after breaking my own arms I was able to pull them into the passenger footwell, and from there, feed them through the holes for the blanking plates below the heater controls.

The switch has 3 terminals: ground, +12v and Accessory. Obviously, +12v should be connected to the positive terminal of the battery, via a fuse. Accessory can be considered the 'ouput' from the switch and runs to the control circuit on the relay. I didn't see anywhere obvious to ground it under the centre console, so I ran three wires through the bulkhead and just wired it with the other negative parts of the circuit to the negative battery terminal with a large ring connector.

The relay is wired thusly: the control circuit takes the (positive) input from the switch, and is also grounded. The load circuit takes +12v from the battery via the fuse and is wired to both LED lights in parallel. The LED lights are grounded directly to the negative terminal of the battery, for simplicity's sake.

Once I'd gotten all the wire lengths right and the whole lot soldered and crimped together I went to town with the shrink wrap, electrical tape and zip ties, and even some bicycle inner tube for the relay. It's not pretty but it could've looked a hell of a lot worse and I'm confident that none of the wires will rub through and short:

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NB: anywhere you see electrical tape is just some extra insurance against the wires rubbing through, all the joints are shrink-wrapped.

I'm sure these lights'll go some way to making sure dear old grandma notices me before she pulls her 3.5k mile beige Vauxhall out of that side turning on her way to buy cat food. Maybe they'll damage her retinas enough to finally get her off the road.

As an added bonus, once it gets dark, I look forward to getting my own back on the d***heads in their BMWs who enjoy blinding you with their full beams. :twisted:

I hope you guys like the way this turned out and if anyone wants more information or a badly drawn circuit diagram, let me know. :thumbsup:

Apologies if none of this makes sense, I've been awake for a looong time.

Edited by Tango91
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