LED Reverse light (Rev. 3)

[soundman98]

i guess it's time to make a thread on this.. been tinkering here and there with the basic design, but with winter approaching, i'm missing the brightness more and more. half the time, i need to double check that my reverse light is actually working at all. the two tiny little 921 bulbs aren't cutting it, and i don't do pnp bulbs..

goals:

• better then revisions 1&2 in terms of brightness, and equal to rev 1 in terms of beam flood, equal to rev 2 in terms of reach.
• less then 3A max current draw overall(1.5A max per side)
• drive all led's @1A
• focus on using xp-g2 3-up star boards for entire design
• COB, and xm-l2 possibility for flood portion of beam pattern
• center section with parking and brake modes
• integrate high-temp cutoff switch for failsafe

the reason for the 3A max draw limitation is because each 921 bulb that the oem housing uses was roughly measured to draw 1.5A each, and connects via a single harness to the car. in my last 2 builds, the car used 1157 bulbs, which consumed 3A per side, which allowed for more design freedom... also, this car has a history of blowing up the body control modules with odd electrical mods. and i would like to avoid having to run wiring to create a relay-activated setup if possible..

for reference, here's the housing i'm using-- an oem replacement housing for the fr-s/brz/gt86/etc model


outer section is the magic reverse part, the center red section serves as a rear-facing fog light in non-american models, i want to make it a 4th parking/brake light..

so first things first, i broke out the plastic calipers(yeah that's right, these, real high-tech stuff) and got the rough housing dimensions imported into progecad to start figuring out what fits and what don't..



next i started playing with the center section, as that's the part that i'm not entirely sure how i'm going to make it work at this point..

first try:


second try, partially completed, not happy with layout:


third try, happy with this as brake mode, but not complete-- want to integrate parking mode as well, haven't figured it all out:


i am going to try using some pointled's in the design.. i've kinda wanted to use them in something for a while because of their interesting design traits, and a parking light is a perfect use.

as far as the reverse section of the housing, i threw this together really quickly, which is a good sign-- none of this lines up, i just threw 20mm star boards in something that resembles a line..


so if all 9 of those boards were 3-up xp-g2 boards, that's 27 individual led's... i definitely need to look into using series/parallel wiring for those, and will need to do a lot of number crunching to keep below 1.5A draw on the input side, and maintain 1A current regulation at each led.. all led's are currently planned to share the same heatsink, so thermal runaway shouldn't be an issue..

i won't know more about the reverse section until i get some heatsink material that i haven't ordered yet...

more to come, comments welcome!

[Ilikecars]

I wish I understood what this all meant lol


Hope it means bright

[KurumaOtaku]

Seeing how little space there is, I assume you won't be using optics for the XP-G2s?
Compared to your last reverse retro, this one is going to be blinding!

[gold94corolla]

I thought you had a thread about this already, but I guess not.

For the red section, I would have all the LEDs do both bright and dim.

Does the car have a reverse camera? Since the housing is so low to the ground, and both lights are right in the center, is that going to make visibility harder? Like driving with only two fog lights in the middle of the front bumper lol

[Speedrye]

How do you work with the grid on? Every time I open an old file, I have to turn that off so that I can focus...

I can see needing more heat sink if you're using the center as a parking/running light, but for braking and reverse, I can't imagine needing too much since those are only intermittent usage. Are you planning for overkill and designing heat sinkage for continuous duty?

[Bitter]

Screw your 3A limit, get a relay and some 0 GA cable back there! Just tap off the sub amp cable.

[soundman98]

I wish I understood what this all meant lol


Hope it means bright

you'd understand better if you made some of your own!

Seeing how little space there is, I assume you won't be using optics for the XP-G2s?
Compared to your last reverse retro, this one is going to be blinding!

i was planning onusing optics-- it's the only way to get the throw i need, otherwise, it ends up similar to revision 1, where it's just all foreground lighting..

I thought you had a thread about this already, but I guess not.

For the red section, I would have all the LEDs do both bright and dim.

Does the car have a reverse camera? Since the housing is so low to the ground, and both lights are right in the center, is that going to make visibility harder? Like driving with only two fog lights in the middle of the front bumper lol

i've posted some in my ride thread, but figured since my other 2 reverse light builds had their own threads, might as well continue the tradition with this one.

i might end up dimming them that way, i just really want to find a use for those pointled's!

car doesn't have a reverse camera, and i'm keeping it that way.. just 3 mirrors, 3 pedals, and me doing the work..

How do you work with the grid on? Every time I open an old file, I have to turn that off so that I can focus...

I can see needing more heat sink if you're using the center as a parking/running light, but for braking and reverse, I can't imagine needing too much since those are only intermittent usage. Are you planning for overkill and designing heat sinkage for continuous duty?

i don't even notice the grid i guess i get too focused on the project, instead of the background..

the center section will all be superflux or smd led's, so no heatsinking needed for any of that. the reverse section, well, 'heatsink' is a poor term... i'm planning on using aluminum heatsink material more like a thermal buffer at this point, where the point is not to immediately dissipate the heat and allow for continuous operation, but to just hold the heat and keep the led's operating safely and effectively for the time that i need them for.. because on average, i will use the reverse lights for around 5 minutes at the most, and then not use them for at least a couple hours, which would give plenty of time for aluminum to drop it's temp down enough to safely operate the light again..

[gold94corolla]

lol I've got the grid off at work, as well as the origin arrows. Never understood their purpose.

I never had a backup camera before, but now I use mine every day backing up against the wall at work in the tiny spaces. I also like it at supermarkets and stuff, just as a 4th view to make sure I'm not backing over someone.

[sprengBoard]

The PointLEDs would be great as the sole LEDs in your park/brake light. A simple PWM is all you need! Do you have the PointLEDs already? If so, what color do you have?

[soundman98]

i've got something like 20 of every color made, just to tinker with, so i'd definitely need to order more for this, or any project i'd use them in... i had an idea a while back to use them for r/c helicopter blade lighting, but they're just too big for that, and i blow through blades too fast to make it worthwhile..

[sprengBoard]

If you recall from the comparison I did a couple years ago, the amber PointLED most closely matches the red-orange SuperFlux in terms of color wavelength (amber PointLED is 617nm typical, red PointLED is 625nm. Red-orange Lumiled SuperFlux is 620nm). The amber is also rated 1000mcd higher than the red (2800mcd vs. 1800mcd) and has a much higher optical efficiency that the others (70lm/W vs. 41-49lm/W for the others). Here's a photo from the aforementioned comparison (from left to right: yellow, amber, red, super-red):

pointleds_all_560ohm.jpg



Here's a shot comparing three amber PointLEDs at 30mA and three Lumiled SuperFlux at 55mA:

Point LED amber vs Lumiled red-orange.JPG

[VegasF6]

Nice, I look forward to this iteration.
I think you may want to consider using fewer white leds for backup. With (27?) leds per side, most likely a 3x9 configuration, or each of the triple stars in parallel, approximately 166 mA per star. That's pretty severely underdriven. It will add to total cost and affect your output temperature as well.
If you don't already have the XPG2 maybe take a look at the XT-E as well, it's so cheap, and the sic cheap is pretty resilient.

Or, if you do want that many leds, for the sake of filling the lamp housing, maybe consider a lower power option cree LED and manufacturing your own copper PCB, which I know you are capable of.
For instance, 27 of the ML-C in a 9x3 configuration, at ~100mA. But then, focusing optics would be a challenge.

[Bitter]

Less emitters driven at higher current with better optics will do what you want more than many low current emitters. Optics on many is hard, optics on few is much easier. Are you going to use lenses or reflectors or both? Honestly, if this were one of my cars I'd just tuck some sealed units under the back bumper, aim, and call it good enough.

[soundman98]

If you recall from the comparison I did a couple years ago, the amber PointLED most closely matches the red-orange SuperFlux in terms of color wavelength (amber PointLED is 617nm typical, red PointLED is 625nm. Red-orange Lumiled SuperFlux is 620nm). The amber is also rated 1000mcd higher than the red (2800mcd vs. 1800mcd) and has a much higher optical efficiency that the others (70lm/W vs. 41-49lm/W for the others). Here's a photo from the aforementioned comparison (from left to right: yellow, amber, red, super-red):

[ATTACH=CONFIG]37266[/ATTACH]



Here's a shot comparing three amber PointLEDs at 30mA and three Lumiled SuperFlux at 55mA:

[ATTACH=CONFIG]37269[/ATTACH]

thanks for the reminder! i believe your review was partly the reason that i bought all the 'sampler packs' of the point led's. i was going to start re-doing the board tonight with all point led's to see what it looks like, but got distracted reading about the FTDI driver bricking fiasco....

Nice, I look forward to this iteration.
I think you may want to consider using fewer white leds for backup. With (27?) leds per side, most likely a 3x9 configuration, or each of the triple stars in parallel, approximately 166 mA per star. That's pretty severely underdriven. It will add to total cost and affect your output temperature as well.
If you don't already have the XPG2 maybe take a look at the XT-E as well, it's so cheap, and the sic cheap is pretty resilient.

Or, if you do want that many leds, for the sake of filling the lamp housing, maybe consider a lower power option cree LED and manufacturing your own copper PCB, which I know you are capable of.
For instance, 27 of the ML-C in a 9x3 configuration, at ~100mA. But then, focusing optics would be a challenge.

the 9x3 configuration is more of a theoretical maximum then a definite game plan at this point-- i could have fit a similar amount of led's in the previous versions of housings as well, but decided against it for both cost and design issues. so more realistically, i might end up with 4 total 20mm boards just to one-up my previous versions, and still maintain a lower overall cost.

also, i believe you miss-understand my (possibly lofty)goal-- i want the drive current at every led to be constant current regulated to 1A, but the final draw of the completed reverse light must be below 3A total, or 1.5A per side.. my current idea is to accomplish this by using at least 1 driver per 2 led's(unclear on weather i'll wire them in series or parallel [need 2A drivers] at this point), though i might need to resort to using 1 driver per 1 led to get the input current level i'm requiring..

it's all a 'figure it out and see' thing for me.. it's part of the fun of tinkering with this stuff!

Less emitters driven at higher current with better optics will do what you want more than many low current emitters. Optics on many is hard, optics on few is much easier. Are you going to use lenses or reflectors or both? Honestly, if this were one of my cars I'd just tuck some sealed units under the back bumper, aim, and call it good enough.

i'm planning on using TIR optics throughout. i believe tir optics offer a lower overall height then a comparable reflector optics.. though there aren't many reflector optics offered for 3 led star boards...

this is just like any other led project for me-- you're absolutely right, there's a bunch of products currently available that i could buy and install in 20 minutes that do nearly exactly what i'm working on designing in my spare time... it's a hobby, just like some people knit (target sells new shirts for less then that yarn!), some restore old cars (a new car is half the cost and twice as fast!), and some people wreck/blowup r/c cars(could just burn the money--at least it creates heat!)... it's something to do that i enjoy doing, regardless of the cost and in today's 'everything can be bought' mentality, it really seems to screw with people when i tell them that i built it instead of just buying it somewhere..

[VegasF6]

also, i believe you miss-understand my (possibly lofty)goal-- i want the drive current at every led to be constant current regulated to 1A, but the final draw of the completed reverse light must be below 3A total, or 1.5A per side.. my current idea is to accomplish this by using at least 1 driver per 2 led's(unclear on weather i'll wire them in series or parallel [need 2A drivers] at this point), though i might need to resort to using 1 driver per 1 led to get the input current level i'm requiring..

So, you have ~12V to work with, and ~3.2V forward voltage per diode. Essentially you are limited to 3 series LEDs. @1A. Or ~12W.
And you want to impose a limit of 3 amps draw for both sides, ~36 watts or so. At best, you can have 9 LEDs in a 3x3 configuration at 1A each. Or 4.5 leds per side (which obviously you can't split an LED in half) so 4 leds per side?

Either I am misunderstanding (and I am many beers in at this point) or you want to violate the laws of physics?