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LED rock lights...

22K views 41 replies 14 participants last post by  General Lee 
#1 · (Edited)
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 :sonicjay:

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. :sonicjay:

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 :sonicjay:

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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#2 ·
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.
 
#6 ·
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.
 
#10 ·
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....
 
#9 ·
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.
 
#13 · (Edited)
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/i41/FlatFender_2006/video/?action=view&current=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).

:thumb:

I'll be sure to get a video after everything is installed.
 
#14 ·
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.
 
#15 ·
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.
 
#24 ·
Dies will get up around 80-120c, on average, depending on ambient temp. But courld see up more than that. It will discolor the epoxy if you put it over the lens.

They actually use certain epoxys (mixed with phosphors to adjust the color) over the lens on some lower power LEDs, but at high temps they will discolor.
 
#29 ·
They don't need AC; they need DC.

Hook them up with in series with a resistor and your 12VDC source.
 
#30 ·
This might be a dumb question, but instead of making turn signal replacement bulbs (and other bulbs like that) with a ton of little LEDs on them....why not just make bigger LEDs? It would be awesome to have one LED the size of a signal bulb with proportionately more light output.
 
#31 ·
They do...you can buy replacement LED bulbs for your regular bulbs out of any 4WD catalog. I had to buy a pair so my front side turn signals would work properly with my converted front grill ones.
 
#35 ·
A few reasons:

1) 'regular' lower power LEDs can run without a fancy power supply, and not much in the way of heatsinking. Cheap, too.

2) Emission pattern. Its hard, without a lightguide, to get enough actual light output from a single, even the bright ones.

Mainly, both of those, sum up to simple economics.
 
#38 ·
Yeah, I figured that was what you were getting at. That is the beauty of Daryl having the 9 LED set-up. He can afford to put one in front of each front tire.

I can't wait for some trail shots/reviews!
 
#41 ·
Thats fine, just like the ones ME used. I use ones like that, but 3 of those per star.

Newbe ? What is a rock light exactly??
Lights under your vehicle to light up t he ground/rocks below you. When driving technical stuff at night, its nice to have the headlights off and the rocklights on for yoru spotter to see whats going on..
 
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