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LED Map lights. 6x Cree XRE (28pics)

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corvettecrazy

Joined: Dec 17 2003
Posts: 4357
Location: moved (twice)


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Post Wed Feb 03, 2010 11:23 pm

Well it has been a while since I have posted any LED projects so here is one of my more recent ones.

I created a ROUGH Proof of concept (POC) just to see how it would work out.

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Rough and Ugly I know but the point of this proof of concept was to test it and learn.

Output (Both are pretty accurate representations of output IMO) (Obviously the LED strips in my foot wells are also on)
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So I decided if I am going to do this, I am going to need to reflow solder the LED's instead of using my soldering iron like I did on the POC and thus I should build a model of what I am going for so I can have a decent example to work from.

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Yes I made my POC before the model, slightly backwards.

Anyway, after the solder paste arrived I began building.

I made templates for the marker from the solidworks model
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Did my first ever board etching, which turned out great considering I did it with a permanent marker in under 10 minutes.
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Then I reflow soldered the board on my stove. This was my first time reflowing with something other than an actual hot plate or reflow oven. Yes the process needed a little refinement, but that is why I did POC bulbs
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Untrimmed board with all components mounted
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On Power supply. You can see the voltage I supplied it and the current it is drawing. (Anything over ~12volts = 350mA constant current operation)
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Trimmed
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Installed WITHOUT stock diffuser/optic
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BULB 3

As you will see, I am getting better.
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Output (These pictures are with the stock diffuser/optic installed)
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Pretty accurate depiction of brightness.
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All my interior lights on. I have LED strips in my foot wells. You can see on the tops of the seats that the dome light is still a regular bulb. That will likely be one of my next projects.
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And for ****, a shot of my rear foot wells.
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Comments and such welcome. Be honest, sugarcoating is for children.
Tim

Joined: Nov 16 2003
Posts: 10795
Location: Kalamazoo, MI


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Post Wed Feb 03, 2010 11:41 pm

That's awesome man. I would like to know if blue is just as bright as white is. I'd love to replace the bulbs in my Lesabre.
corvettecrazy

Joined: Dec 17 2003
Posts: 4357
Location: moved (twice)


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Post Wed Feb 03, 2010 11:55 pm

Thanks. Bright white would be the best way to describe it. 3500-5000k is the color binning on the LED's. And don't bother trying to compare that to the **** colors of HID kits because when I say 3500-5000k I mean measured with a spectrometer, actual color temperature.
Moss

Joined: Mar 23 2004
Posts: 6436


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Post Thu Feb 04, 2010 12:11 am

Very sick, that's a legit little design you got going on. Reminds me of some of the older cooler projects that people used to take on on here.
Phil
Owner, Oznium.com

Joined: Feb 11 2003
Posts: 7721


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Post Thu Feb 04, 2010 4:16 am

What's the cost of each LED? And where did you source them? Could you have used a smaller (physical) voltage regulator? What's the length from end to end? 45mm? Is heat output a concern? The copper board surely dissipates some heat, but what if these LEDs were not mounted on a heat sink, and just left in thin air, would the heat be OK? Would a warm white actually be better for visibile function in the car? I'm worried the cool white might be too harsh. What happens when your domelight dims when the doors are shut, and the voltage swings down to 2 or 3, and then off? Or if your car doesn't do this, what would happen? Could it handle it gracefully, and dim, or would it either be on or off, and perhaps flash when the voltage is too low? So the current draw is 350mA? Why did you reflow solder, and not just solder by hand? I wonder how the light output / brightness lumens compares with Ozniums 16 LED superflux 4chip dome light? We have heat issues with them, and if left on, get too hot to touch. Related to the heat output of these Cree, I wonder if they could be mounted on say, a double layer flexible board. Did you damage any LEDs in the process?
Tat2Dragons

Joined: Jan 21 2007
Posts: 3404
Location: Baltimore Maryland


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Post Thu Feb 04, 2010 6:26 am

Cool project,the output and color looks great. icon_cool.gif
Grinder

Joined: Dec 29 2007
Posts: 83


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Post Thu Feb 04, 2010 8:26 am

what size strips do you have in your footwells?

ive been following this on one of the bonneville forums. i want one or 2. lol
corvettecrazy

Joined: Dec 17 2003
Posts: 4357
Location: moved (twice)


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Post Thu Feb 04, 2010 8:52 am

Moss wrote:
Very sick, that's a legit little design you got going on. Reminds me of some of the older cooler projects that people used to take on on here.

Tat2Dragons wrote:
Cool project,the output and color looks great. icon_cool.gif


Thanks guys.

And Moss, you know how we do, none of this noob ****. biglaugh.gif

Phil wrote:
What's the cost of each LED? If you just bought the LED's in bulk I believe they begin to fall into the 3ish dollars per LED range. Buying them in small quantities on the web puts them into 5-7 dollars per LED

And where did you source them? The waste bin at my last job. These are 2006ish era LED's and their output is half of the modern Cree XR-E thus they were no longer needed.

Could you have used a smaller (physical) voltage regulator? It is a voltage regulator set up as a current regulator. They do make them in a smaller package size but I had these already.

What's the length from end to end? 45mm? The board itself is about 32mm long and maybe 2-3 mm longer due to the copper pipe overhang. So let's go with 35mm.

Is heat output a concern? Absolutely. But because I made pretty much all of it from scrap parts I had around, if one blows then I'll just make another one. I wouldn't suggest holding one of these in your hand after it has been on for 45 seconds. You'll be playing hot potato with it.

The copper board surely dissipates some heat, but what if these LEDs were not mounted on a heat sink, and just left in thin air, would the heat be OK? My test LED was one with wire leads soldered to the bottom and it just floats in the air. It can definitely be done, but my guess is that you won't get anywhere close to the lifetime ratings because of the heat build up. My guess is that I could get the LED hot enough to melt the solder off the leads before it blew, but doing that can't be good for it.

Would a warm white actually be better for visibile function in the car?I'm worried the cool white might be too harsh. Yeah it would probably be nicer, and they do make these LED's in warmer colors. I can't complain because of the price though.

What happens when your domelight dims when the doors are shut, and the voltage swings down to 2 or 3, and then off? Or if your car doesn't do this, what would happen? Could it handle it gracefully, and dim, or would it either be on or off, and perhaps flash when the voltage is too low? On my car they do dim slightly then go off. It is more of a 2-3 step flicker than dimming. I believe this is caused by a few things. Since I only have 1 bulb left that is incandescent there is significantly less load on the circuit and I think that is messes with how it dims. Also because these go through a current regulator, they will not dim until the voltage drops below the Vmin of the regulator. Once below Vmin, the "dimming" is no linear and very fast. I'll try to get a video of that in the next few days.

So the current draw is 350mA? Yes, because I am regulating the current to that. Current regulation is considered necessary for this kind of higher power LED. If they are not current regulated you can get thermal runaway. (more heat caused higher current draw, which causes more heat, which causes higher current draw...you get the picture) Also, unregulated one LED would pull almost an amp and the heat generation from that is crazy.

Why did you reflow solder, and not just solder by hand? I soldered the first one by hand and it really just made a mess of things. Reflow soldering meant that I can easily solder all 6 +/- pads and the large thermal pads at the same time, only heating the board once. When doing it by hand I now have to heat the board 9 times as I have to do each part of the LED by itself. This just puts extra heat wear and tear into the LED's that isn't necessary, but it is possible.

I wonder how the light output / brightness lumens compares with Ozniums 16 LED superflux 4chip dome light? The bin codes on these LED's state that lumen output is between 30-50 per LED. From all the Cree LED's I've measured, they are normally pretty close and honest about their ratings. So you are looking at 90-150 per side at 350mA. If I broke out my stash of modern Cree XR-E then we could be talking 50-100 lumens per LED at 350mA

We have heat issues with them, and if left on, get too hot to touch. Related to the heat output of these Yeah I wouldn't suggest holding this bulb while it was on for anything more than 30 seconds.

Cree, I wonder if they could be mounted on say, a double layer flexible board. I'll have to take some pictures of the flexible board that I have, it's pretty cool.

Did you damage any LEDs in the process? I damage them all the time. The dome on these LED's rests inside the metal reflector ring but under the dome is a soft gel like substance. If you push too hard (which isn't that hard) on the dome you will pop it right off. The LED will still work, but the output looks like crap. I also don't know how long it will last with the dome off, but I would imagine the life is limited


Phil you didn't have any questions did you? haha

The front foot wells are thee ultra flexible Tri-chip strips.( https://www.oznium.com/flexible-led-strips/flexible-tri-chip-ribbon-leds ) I used 1 in each foot well.

The rear foot wells were done by taking on of the waterproof SMD bars ( https://www.oznium.com/linear-lights/smd-bar ) cutting it in half, and putting 10 inches of it on each side.
Black DX

Joined: Oct 16 2007
Posts: 1007


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Post Thu Feb 04, 2010 1:57 pm

do the cree's have a center based heat sink pad? I'm thinking a way to help the heat issue is to either leave a stip of copper under the led's or carve an opening and slot a copper slug or rod into the middle of the board...

Either way looks good, I've not got the trust in myself to work with high heat/high cost led options but I do enjoy seeing the things people come up with...
corvettecrazy

Joined: Dec 17 2003
Posts: 4357
Location: moved (twice)


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Post Thu Feb 04, 2010 6:22 pm

They do have a neutral thermal pad and I did solder that to the rectangle of copper that is on the board. Problem is that because I went for such a tight package, there is pretty much no volume of copper so the fiberglass in the board has to take over. (Which is does a decent job at)

They really aren't that hard to work with, it is just different.
Radioflyer

Joined: Sep 25 2007
Posts: 1563


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Post Sat Feb 06, 2010 5:36 pm

where did you get the soldering paste?
corvettecrazy

Joined: Dec 17 2003
Posts: 4357
Location: moved (twice)


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Post Sat Feb 06, 2010 11:41 pm

I got it from mouser I believe but I would suggest looking into a different paste. Yes it is cheap at 5 bucks per tube BUT the size of the pieces of solder are not very fine at all. Makes fine surface mount stuff very awkward to paste.

You can sort of see the "grain" size in this picture.

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I personally would not buy it again. Maybe I was just spoiled with nice paste at my last place of employment, but IMO it would be worth the extra money to buy some nicer stuff.
saisofine

Joined: Apr 26 2009
Posts: 259
Location: florence, OREGON


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Post Sun Feb 07, 2010 4:03 pm

wow those are nice. bright and clean light. i like
corvettecrazy

Joined: Dec 17 2003
Posts: 4357
Location: moved (twice)


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Post Tue Feb 09, 2010 2:29 pm

Phil, the pictures of a flexible board are below. It is fun to play with but I wouldn't suggest leaving it on, while not pressed against a heat sink for long.







Picture of knocking the lens off of a Cree XR-E
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