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Old March 18th, 2008, 12:27 AM   #1
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LED rock lights...

By the time you finish these, it's probably easier to just buy the damn kit from roundeyes... but that is not as much fun

First things first... you need some LED's.

How about some 3w Cree P4 XR-E's?

Here is a 5 pack for $21 shipped.
http://www.dealextreme.com/details.dx/sku.2134

I ordered 6 total, I really need 8. I will have to work that out later.

Ok, here we go.

These LED's and stars get REALLY hot. They need a heat sink to properly cool, I figured I would make my housings thick enough to not have to worry about it.

This is a 2.5" wide chuck of aluminum drop from the local metal supply. It's .250 thick. I cut it to widths of about 1.25.


Milled a 7/8" hole just under 3/16" deep... I am not a machinist, so we are defiantly not talking in thousands here.


Milled a channel for the wires, and drilled some mounting holes.


Drilled and tapped some holes for the cover.


My test pieces, one clear, one I scuffed with 80 grit to try and get some diffusion.



Mockup.


Have a gap issue since the emitter sticks above the aluminum a little still.


Hard to tell in this picture, but I drilled a dome on the inside of the lens for the emitter to sit in, lens now sits flush.


It's a lot easier to see what is going on with a camera... when I took this picture the shop lights were on, and I still couldn't look at the damn thing. I am driving it with a 6v AC adapter for testing.


Test on the Cruiser since it was handy

Clear lens.


Diffused lens. The camera changed the shutter speed on this picture. While the diffused lens does spread out the light slightly better, it is not brighter like this picture would make it appear.


That's it for now. I need to get some heat transfer paste, then I can epoxy the stars to the heat sinks and finish up the final lenses.

I'm driving them with a board that General Lee built for me, you can use resistors if you want as well... a driver board is just way more efficiant and better for the LED's.

I only had him build it for 6 LED's though.. so I kind of shot myself in the foot on that one.
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Old March 18th, 2008, 12:45 AM   #2
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A word on using LED's. Brian has incandescent driving lights on his FJ-40. He uses 6, one under each wheel well, one in the front and one in the rear. This lights up almost everything under his rig and them some. It's got a great throw.

To have comparable illumination under my rig I will need to run 8 LEDs. One under each wheel well, one above each slider, and one in the front and rear. This still will not throw as far as a 55watt driving light.

The benefit to using LED's is size, life, and power draw.

While 6 55watt driving lights will draw 23 amps at 14 volts.

8 3w LED's will draw almost an 8th of that depending on the driver.
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Old March 18th, 2008, 12:48 AM   #3
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Old March 18th, 2008, 07:29 AM   #4
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Are those waterproof and sealed and :chiefwoohaw:? I can't believe how bright those puppies are. I would love to get some of those for interior lights on the YJ.
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Old March 18th, 2008, 08:31 AM   #5
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They will be sealed when I run a bead of silicon inside the lenses when I finally assemble them.
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Old March 18th, 2008, 08:36 AM   #6
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Are those waterproof and sealed and :chiefwoohaw:? I can't believe how bright those puppies are. I would love to get some of those for interior lights on the YJ.
They could be, with some silicone to seal them.

For interior lighting, they work well.

My experience is the same as ME, that 8 is the magic number, for that size part (a P4 bin is 80 lumens @ 350mA).

I'm building a new set with Endor stars (3 x 80Lm on each star), so I might get away with 6 on the new vehicle.

I will post a schematic of a constant-current power source you can make for $10 with a few radio shack parts.

A few tips if someone is making these:

1) check your part datasheet, to make sure the thermal-core PCB is electrically isolated. On single LED boards, is sometimes isn't isolated, which shoudl short if you screw the aluminum to the frame

2) Use some computer heatsink compound behind the star to get a few thermal transfer to the aluminum.

3) If you don't have a mill, buy 'gem jars' on ebay, they are little flat glass/plastic jars that you can get dirt cheap, they make nice lenses.


I think the next thing I'm looking for, is better diffuser material. LEDs like this are lambertian emitters, usually 90 to 120 degree, but most of the light is in about a +/- 30* cone.



Looks nice! I liked the milled flatbar idea. I'll have to try some different diffusion material I have here at work for some tests.
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Old March 18th, 2008, 08:40 AM   #7
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If you feel the need for spending lots of cash, check these out (I'm using a cheaper version of this...)

http://www.luxeonstar.com/item.php?i...=7007-PWC-10-3

One of these = 7 cree P4s...
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Old March 18th, 2008, 08:56 AM   #8
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Those are still way to expensive for me... I remember when the P4's were almost as much though.
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Old March 18th, 2008, 09:05 AM   #9
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IMHO, JCR should offer the parts you made for sale.

I do not need "rock lights" per se, but I would run the six around the underside of my pickup camper so I can see better setting up at night and maneuvering around the campsite looking for a place to pee.
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Old March 18th, 2008, 09:06 AM   #10
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Those are still way to expensive for me... I remember when the P4's were almost as much though.
Yeah, they get real expensive as the intensity bins go up..

(quick note on LEDs: When the manufacture them, they are all measured, then sorted by color, brightness, and sometimes voltage drop. They call these bins. For cree's, P4 is the intensity bin for that part. A P5 would be brighter with the same current, a P3 would be dimmer).


I use the 240 lumen ones from this company:

http://www.ledsupply.com/endorstar.php

But I will run them at 700mA, so they'll be equivelent to 6 of the P4s....
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Old March 18th, 2008, 10:25 AM   #11
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Cool write up!
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Old March 18th, 2008, 03:58 PM   #12
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Take this over to www.candlepowerforums.com

You will have people THROWING money at you.
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Old March 18th, 2008, 05:22 PM   #13
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Nice work Daryl!

Just to give some more info on the boards I'm working on and the advantages thereof (shameless plug, I know...):

The board I designed for Daryl is a 500mA model capable of powering 6 LEDs on 13.5ish volts. (I am currently working on a 2A model.)

The advantages to this board over using resistors to set current are HUGE.

First off, the principal behind a resistor is to set a current based on an assumed consistent voltage. If you have 14 volts and your LED drops 3.7 volts (14-3.7 = 10.3 volts left over). If you want 1A, lets say, you need a resistance such that 10.3/R = 1 or a 10.3 ohm resistor. The resistor wastes 10.3 watts PER LED while in use, AND, if, for any reason, your voltage spikes, your current will also spike (since your resistor can't adjust for the change). This could possibly result in a blown LED...and they're expensive.

Also, with resistors, you miss out on a plethora of functionality that could be utilized better with a driver board.

The board I designed for daryl burns approximately 3 Watts Total MAX. It can also handle voltages up to 18V for a couple of minutes and spikes up to 40V for a few ms.

Plus I added a 8.5 Hz strobe for fun (I can also add dimmers/patterns/whatever).

Here is a little video of the functionality (Sorry, the quality isn't the best, and I didn't have a switch, so I had to just touch the bare wires together):
http://s69.photobucket.com/albums/i4...Picture007.flv
The LEDs in that video were also weaker than the ones that Daryl purchased.

I'm thinking about starting some side businesses with some minor electronics, and, provided I had enough people interested, that would be a featured product.

Also, as a side note, we were trashing a bunch of these heat sinks at work, so I saved them from the trash can:

These are light weight aluminum and would work well for this type of application (if you needed something more lightweight). (You'd have to cut the channel for the TO-220 off to use them with the LEDs, but it'd be easy to modify).



I'll be sure to get a video after everything is installed.

Last edited by General Lee; March 18th, 2008 at 05:32 PM.
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Old March 18th, 2008, 06:44 PM   #14
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Yeah, unless you want to run them at much less than full power, or risk damaging them, using resistors for high power LEDs is not recommended. Its a fine method for small LEDs, though.

The issue is that every LED has a different voltage drop across it, and that drop will vary based on several factors, including temp.


The way to run them is a constant current source. What you can do, is put them in series, as many as practical.

For OEM designs, we run 2 whites in parallel, because we need to run at 9 volts. On a wheeler, Honestly, if the voltage is below 12 volts, then I have other issues..

So, I run 3 whites in series. Then I use an adjustable linear regulator configured to create a constant current source. Cheap and simple.
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Old March 18th, 2008, 08:44 PM   #15
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Quote:
Originally Posted by Haggar View Post
Yeah, unless you want to run them at much less than full power, or risk damaging them, using resistors for high power LEDs is not recommended. Its a fine method for small LEDs, though.

The issue is that every LED has a different voltage drop across it, and that drop will vary based on several factors, including temp.


The way to run them is a constant current source. What you can do, is put them in series, as many as practical.

For OEM designs, we run 2 whites in parallel, because we need to run at 9 volts. On a wheeler, Honestly, if the voltage is below 12 volts, then I have other issues..

So, I run 3 whites in series. Then I use an adjustable linear regulator configured to create a constant current source. Cheap and simple.
Ever consider a buck converter?

I've designed circuits at work that power 22V worth of LEDs on 9V.

Admittedly, you don't get AS much current as something that has the voltage to back it up without the buck, but it's another thing to consider.
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Old March 18th, 2008, 09:06 PM   #16
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Ever consider a buck converter?

I've designed circuits at work that power 22V worth of LEDs on 9V.

Admittedly, you don't get AS much current as something that has the voltage to back it up without the buck, but it's another thing to consider.
We never use them at work, because the cost can't be justified for what we do, until the OEMs change their specs. But I have 'free' pwm controllers onboard my designs, so we control intensity that way.

But, yes, for driving for hobbies, a DC/DC works well. technically, thats a boost, though, buck is knocking down the voltage....


I get to play with this stuff a lot more at work now. I just got named as our north american LED techincal expert for my company.
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Old March 18th, 2008, 09:43 PM   #17
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Quote:
Originally Posted by Haggar View Post
We never use them at work, because the cost can't be justified for what we do, until the OEMs change their specs. But I have 'free' pwm controllers onboard my designs, so we control intensity that way.

But, yes, for driving for hobbies, a DC/DC works well. technically, thats a boost, though, buck is knocking down the voltage....


I get to play with this stuff a lot more at work now. I just got named as our north american LED techincal expert for my company.
Buck, boost, same difference :tonka: (sorry, I'm tired!)

I understand that you guys want to save money at the cost of more power wasted, but I build more for efficiency.

I want to have rock lights that are as bright as the incandescents that I can leave on for several hours without frying my battery (in case I need to crawl under the jeep and do some work or something of that nature).

Again, though, you're losing out on some functionality. My set-up allows me the option of a PWM brightness control, or a DC signal voltage level to control brightness (and, of course, there are more advantages to this), which is flippin' convenient.

Congrats on your promotion.

I don't deal with LEDs too much. I've only recently picked up an interest with them when I was assigned to a project where I use infrared LEDs and infrared receivers to communicate and build a virtual 3D grid in free space (they can also communicate several other things, but that is the neatest part).

Kinda' cool stuff!
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Old March 19th, 2008, 10:02 AM   #18
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Buck, boost, same difference :tonka: (sorry, I'm tired!)

I understand that you guys want to save money at the cost of more power wasted, but I build more for efficiency.

I want to have rock lights that are as bright as the incandescents that I can leave on for several hours without frying my battery (in case I need to crawl under the jeep and do some work or something of that nature).

Again, though, you're losing out on some functionality. My set-up allows me the option of a PWM brightness control, or a DC signal voltage level to control brightness (and, of course, there are more advantages to this), which is flippin' convenient.

Congrats on your promotion.

I don't deal with LEDs too much. I've only recently picked up an interest with them when I was assigned to a project where I use infrared LEDs and infrared receivers to communicate and build a virtual 3D grid in free space (they can also communicate several other things, but that is the neatest part).

Kinda' cool stuff!

When we have heat specific, we can and do use buck regulators.

Thing is that for high power (InGaN) parts, we can't use current control for changing intensity, only the PWMing. (A typical LED circuit would have a PNP transistor no the high side for PWM control, the LED, then current limiting resistor, then an NPN switch on the low side for on/off control. ).

Resistors are binned at a specific current, which is the only point their characteristics are guaranteed, usually. What happens is that as the current changes, the X-Y color coordinates change as well. Its especially noticeable in the whites, and we have tight specs for the color coordiantes.

But, in the production world, cost is key. one of the projects I'm doing now, I took 3 cents out per LED, which at our volumes saves us $1.7M per year, so little things add up. I think my current prorgam is using 41M LEDs per year...
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Old March 19th, 2008, 10:07 AM   #19
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Old March 19th, 2008, 12:07 PM   #20
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Quote:
Originally Posted by Haggar View Post
When we have heat specific, we can and do use buck regulators.

Thing is that for high power (InGaN) parts, we can't use current control for changing intensity, only the PWMing. (A typical LED circuit would have a PNP transistor no the high side for PWM control, the LED, then current limiting resistor, then an NPN switch on the low side for on/off control. ).

Resistors are binned at a specific current, which is the only point their characteristics are guaranteed, usually. What happens is that as the current changes, the X-Y color coordinates change as well. Its especially noticeable in the whites, and we have tight specs for the color coordiantes.

But, in the production world, cost is key. one of the projects I'm doing now, I took 3 cents out per LED, which at our volumes saves us $1.7M per year, so little things add up. I think my current prorgam is using 41M LEDs per year...
Yeah, I don't mass produce, so I just shoot for quality.
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