MR2 Turn signals


Just to preface this, I have a pretty ok grasp of electronics, I like to think i know enough to be dangerous, but im definitely no expert.

I recently made some replacement 3rd brake lights for my car and its got me wanting to make some turn signals since the OEM ones leave a lot to be desired. The thing I want most is a nice even output across the whole lens, which im having trouble with since the lens is curved, and im not sure how to curve a PCB to follow the lens. Does such a product exist, or should i find a better way to light it?


You might use leads instead of trying to solder directly to the PCB.


OSH Park has started doing 2-Layer flexible interconnects. (I’ve never used their services)


If i do that is there a good way to hold the leds behind the lens?


Thats what i want, but they’re a little more expensive than i want. I’m definitely going to look in to them though.


I would use a piece of thermoplastic for a mounting surface. Cut/shape to fit. Fix it with a viscous adhesive (silicone?).


I agree. They are pricey. Seeing this comment …

“For example, a 2 square inch board would cost $30 and you’d get three copies of your board.”

makes me wonder if one could get clever with the layout such that if you wanted a 6" x 2" interconnect and your design is essentially repeating, one maybe designs a 2" x 2" interconnect and you kind of / sort of end up with a 6" x 2" with some clever connecting of the 3 flexible interconnects. (Of, course this hypothetical still leaves you with $30 / headlight).


Thats not a bad idea. maybe i can get some cheap plastic and bend it up with a heat gun and see what i can make it do.


i wouldn’t have thought about that. maybe i can do that. i might get a test piece from them just to see what it would look like behind the lens and how well it would work for my application.


The “classic” way to achieve a curve with PCBs is to have multiple flat PCBs at slightly different angles, connected with wires. Something like this: \_/ as opposed to U.

The other thing you can do is angle the LEDs themselves on a flat PCB so that they point in different directions. This is even possible to some extent with surface mount LEDs if you are soldering them by hand, but it’s a total hack.


oooh make me some too. Maybe a group buy in the future?


Thats the plan. I assume that im invisible at night so i wanted to modernize the lighting on the car. I got some sweet 3rd brake light replacements too if you want one of those.


Flex PCBs aren’t exactly known for vibration resistance. Solder joints, especially with large or heavy components, are good places for cracks to form long term.

I’d recommend forming some plastic to fit, mounting lights to that and wiring them up.


Another potential is “light pipes”.

Automakers use them for the lit interior trim you see.

I’m not sure how well they work for high intensity effects (brake lamps/turn signals/DRLs). Automakers have the economies of scale to just make the tooling right the first time when we call out those effects on new cars.

I’d like to echo the caution against flex-PCBs. They’re garbage when it comes to temperature and vibration resistance, especilly when hand-soldered.


If i could get the kind of smooth output from the light pipes on to the lens of the turn signal that would be perfect. Maybe cool to run a light pipe around the perimeter of the lens for a cool tron-esque outline. Im starting to think that Doing what @DavidGood suggested with multiple smaller PCBs and maybe try and make the switch to SMD stuff instead of through hole components to just to try and cram more LEDs in there for a more even light across the lens. That being said i have zero experience with SMD components.


I also just found this, its only 2mm thick and if 2700k color temperature looks good through an amber turn signal lens then it might just be what im looking for.


Light pipes to use would be different in this case… they would be a pipe that fit straight out from the end of the LED but you would adjust the length of to fit the curved surface of the lens. The light would just come out of the end of the pipe.

The hard part will be getting the mirror clean surfaces on the ends of the light pipes after cutting to fit.


I’ve given up on flexi things. I have a plan i just need some time to get it together and see if itll work for me. I do still want some sort of film or translucent plastic to sit behind the lens to even and smooth out the light on the lens, though im not sure what im gonna use for that yet.