# Basic (VERY) LED star emitter wiring



## davehiro (Oct 3, 2008)

I am looking to wire up an LED star for a project and want to do this in the easiest fashion possible- I would like to use a 300+ lumen if possible- but most LEDs on dealextreme (where I have been looking) don't display lumens.

Can anyone recommend a high lumen LED star setup, and the most basic wiring for it? I really just need something like a few AA's in a battery holder hooked up directly to an led star. 

what I have been looking at:

http://www.dealextreme.com/details.dx/sku.2394


----------



## tebore (Oct 3, 2008)

They are listed: * 350mA: 107~114lm * 700mA: 171.2~182.4lm * 1000mA: 214 ~ 228lm lm = lumens


----------



## R33E8 (Oct 3, 2008)

I would use a MC-E or SSC P7...


----------



## Oznog (Oct 3, 2008)

300 is a LOT for one emitter. I don't mean to be critical or rude but you don't seem to be intimately familiar with LEDs, so where'd you decide you needed 300 lumens? It kinda sounds like you might have just picked 300 out of the blue.

So, what do you want to do? Make a flashlight? A light for a science project? What?

You need a regulator board, DX/KaiDomain sell a lot of them.

Running devices at 2x or 3x their nominal rating really stresses the heatsinking solution. They do get less efficient and typically the die temp rises and it may degrade or fail in far less than its rated hours. It works if you have a great heatsinking solution and you have a flashlight you only planned to use for a few dozen hours total anyways. Plus you have to really be unusually excited about getting a lot of light! 350mA can be a fairly bright flashlight to begin with.


----------



## davehiro (Oct 3, 2008)

Thanks for the info- and no I have no knowledge of LEDs, I have done wiring for fluorescent fixtures in the past, and basic soldering for those projects...

I want as many lumens as possible in a small package, for making lighting that can be worn taped to a persons palm for performances- I realize that the high lumen LEDs can get pretty hot though. as for the 300- These performances will be photographed, so i thought that 600 lumens (about a 40-50 watt light bulb) or around that would be enough light for the scene.

I was thinking about getting a couple 4 packs of boards and LEDs and see if I can get a couple not broken wirings out of the deal...


----------



## R33E8 (Oct 3, 2008)

I would go for a MC-E for most light in a small package... It you want even more light you can try going for a high brightness led array... They aren't as efficient but some can emit over 2000 lumen...


----------



## davehiro (Oct 4, 2008)

I think I found what I wanted!... I read this post-
https://www.candlepowerforums.com/threads/140127

and saw a post where someone used a 3.6V 650 mah battery with no regulation- though they never stated if they used a resistor or if it was direct drive. 

(this battery)
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1389

Do you think I could just make a battery holder (or rig a C size holder since this battery is a bit smaller) and use it to directly drive a CREE XR-E?


----------



## Stillphoto (Oct 4, 2008)

Sound like you want to do the Kanye lighted glove thing...you've seen this page right? 
http://www.enlighted.com/pages/gloves.shtml


----------



## davehiro (Oct 4, 2008)

Stillphoto said:


> Sound like you want to do the Kanye lighted glove thing...you've seen this page right?
> http://www.enlighted.com/pages/gloves.shtml



oh goodness gracious. No I haven't haha. Well I thought I was a little original but... 

I envisioned it differently anyways... the star heatsink backed with a rubberized substance, and then used medical tape to adhere it and run wires down the arms to the battery pack... so in low light, even when you have the palms facing out you don't see anything but the light.


----------



## Oznog (Oct 4, 2008)

Ah, an innovative artistic project. You now have my attention.

A Star with no heatsink running at >3W will overheat in short order. I guesstimate under a minute before it starts to burn your hand and/or cook the die. Insulating the backplane so you don't burn your hand sounds nice but that makes the conditions for the die heat much worse. But the front will still be exposed and very hot unless you cover that too.

Maybe add some alcohol gel hand sanitizer stuff to it? That cools a lot as it evaporates and the evaporation & cooling accelerates as it tries to heat up, and will extend the runtime until overheat albeit not indefinitely. Actually, trying to _maximize_ the heat transfer to your palm may be of merit. It will be hot but may never reach burning hot temperatures due to the constant heat exchange.

Actually for size, the Rebels are pretty much tops. Those are up to 100 lumens per pkg nominal and they're super-tiny. 

The direct-drive thing is not nice. The current is inconsistent and unpredictable, it can easily draw too much current. A ballast resistor at least would be really helpful but trying to run a white LED off a 3.6v batt offers no headroom. A lithium is 4.2v to 2.5v and a ballast resistor can't regulate over that range on a white LED. 3x NiMH batts is a mostly constant 3.6v as long as you don't ask for a whole lot of current from small batts but even still there's so little headroom. Now keep in mind these flashlights regs are only quarter-sized which isn't too bad really.

I'm thinking the alcohol gel cooling might really suit your needs there. Unusual, weird, but sounds dead-on appropriate.

I don't think those gloves are using 300 lumen emitters. Maybe like 25, 50. Maybe 100 tops. For 3W of LED power, you need to pay attention to the batt size. A single garden variety NiMH AAA probably can't do it even with a boost reg even though it has enough mAH to last the performance. They can't _deliver_ power at that rate. This is going to be a problem with a lot of the super-tiny batteries you might want to try to fit inside the glove.

Hey, remember the "gumstick" NiMH batts?






These come to mind because:
1. They'll fit inside the distance from back of the wrist to behind the first knuckle. That direction is braced by bone and doesn't bend.
2. 2 or 3 can be placed side by side so the pack will bend with the glove. That direction DOES need to bend.
3. They're flat.

Oh hey they make li-ion gumsticks now:





But you need to consider the power delivery capability there too. 300 lumens = ~1 A @ 3.7 V, which is nearly a 3C discharge. Probably too much for that little batt it wasn't designed as a high-rate.

And the li-ion at 3.7V 370mAH is less watt-hrs than the 1.2v 1400 mAH NiMH. I bet 3x NiMH in series will deliver more amps than the 3.7V li-ion there AND it has more total capacity.


----------



## davehiro (Oct 4, 2008)

Oznog- Lets say I were to stack a CREE XR-E Q5 star on top of this driver http://www.dealextreme.com/details.dx/sku.3256

with short stand-offs like so... 
.......star.............------=O=------
.stand-offs.............[_________]
......driver.............--[]---o--O--
......palm........||||||||||||||||||||||||||

and after the wiring have the driver dipped in plasti-dip as an electrical and thermal insulation for the palm... There would then be air able to flow around the star itself... or would that be less beneficial- taking away the palm as the star's flesh heatsink?


----------



## R33E8 (Oct 4, 2008)

The board the led is mounted on is not really a heat sink.. It's just a piece of metal that makes the emitter easier to solder and mount the board onto a heat sink while electrically isolating the emitter from the heat sink and providing a good thermal path... To cool down almost 3 watts of heat is going to take a heat sink that is fairly large compared to your hand... Unless you want to try making some type of diamond or directional carbon heat sink:shrug:... What do you need 300 lumen for anyways? I think you may be underestimating how bright 300 lumen of directional light is..


----------



## Oznog (Oct 4, 2008)

davehiro said:


> and after the wiring have the driver dipped in plasti-dip as an electrical and thermal insulation for the palm... There would then be air able to flow around the star itself... or would that be less beneficial- taking away the palm as the star's flesh heatsink?



Like R33E8 said, even if the Star was left suspended in the air it cannot dissipate 3W. 3W is a lot of heat. It will overheat in maybe a minute or so. It's a heat _spreading_ mount without enough surface area to actually transfer heat to the air. IIRC a 1W Star won't overheat if it open air without a sink but even then it will get hotter than it needs to be.

The front of a Star is covered in masking not exposed metal and surely has a very poor dissipation coefficient. It's just not going to work there. Not continuously. Your only hope is that the aluminum has enough thermal mass that it won't overheat before the performance is done but that's probably under a minute unless you add some more thermal mass behind it. You don't really have room though.

The flesh being able to cool the Star is just a theory. I can't say if it'll work. I'm still on the alcohol gel soak idea. I still think that's dead-on what you need.

A custom heatsink MIGHT be in order. Fins or exposed metal in front. But you don't want to cut up your hands on them and that presents a problem. Really difficult problem actually. An alcohol gel soak might still need a custom sink solution too.


----------



## Calina (Oct 4, 2008)

I don't think a high power LED will stand to the abuse of a performance. There is a high risk that it will get knocked off. If I were to try something like this, I would go with 5mm LEDs. These are surprisingly bright and you will not have to deal with the heat problem. Try to experiment with these : http://www.dealextreme.com/details.dx/sku.4241 
or an equivalent; they are not expensive.


----------



## Oznog (Oct 4, 2008)

Calina said:


> I don't think a high power LED will stand to the abuse of a performance. There is a high risk that it will get knocked off.



Ah great point!

Some like Rebel have a silicone lens, others like the original Luxeon emitters use acrylic. Either one is prone to damage here. You can break off the acrylic or peel off the silicone if the force is right. In fact spec sheets emphasize that there's only a few accepted ways of handling them during installation.

Of course you may just want to accept that loss, I mean even if a performance has a 20% chance of breaking one that's not unmanageable if you can just swap it out. But if it's an install requiring jigs and tools and machining then maybe it IS a big deal.


----------



## Oznog (Oct 5, 2008)

Calina said:


> I don't think a high power LED will stand to the abuse of a performance. There is a high risk that it will get knocked off.



Ah great point!

Some like Rebel have a silicone lens, others like the original Luxeon emitters use acrylic. Either one is prone to damage here. You can break off the acrylic or peel off the silicone if the force is right. In fact spec sheets emphasize that there's only a few accepted ways of handling them during installation.

On many emitters like the Luxeons, they stand up tall and are thermal epoxied onto the Star. A good knock from the side and it can break them off the board. Or, as I found out once, the entire housing can be knocked off leaving the thermal pad and emitter glued to the Star.

Of course you may just want to accept that loss, I mean even if a performance has a 20% chance of breaking one that's not unmanageable if you can just swap it out. But if it's an install requiring jigs and tools and machining then maybe it IS a big deal.

A cover would be nice. But there's a room issue and the mouting of a cover could cover up a lot of the front area that was the last bit of heat dissipating space we have left.


----------

