10mm 280K MCD dome leds, heatsink and relative brightness?

[VegasF6]

Related to my other post here:
http://www.candlepowerforums.com/vb/showthread.php?p=2438075#post2438075

For a general lighting project, maybe auto, maybe home, maybe who knows what, I am curious about using these leds:
http://cgi.ebay.com/ebaymotors/50p-...022QQitemZ350047904268QQrdZ1QQsspagenameZWDVW

I would like to know how the 280K MCD compares to a cree P2 or P4 at 350ma. For instance, the P2 is rated at 67.2 lumens, the P4 at 80.6

Apparently there is no apples to apples way to convert candle power (or MCD in this case) to lumens, so how do I compare the cree's to the dome lamps?

Also the max operating temps for the dome lamp is roughly equivalant to the cree hi-power lamp. So, assuming an infinite power source, pennies to pennies which would be brighter? 4 dome lamps in series vs one P4, and would heatsinking need to be equal in each case?

Thanks!
VegasF6

 

[Wok]

Hi,

Been working on this http://cgi.ebay.com/20pc-HP-10mm-40...photoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

It is a subjective comparison because these are warm-whites & the pattern is very diffused c.f to Cree Q2 [WH]....I get more usable light on the ground [camping application] up to about 4m.This is driven @ 800mA total [80mA per 4 series string]. It hardly gets warm @ this current.
I think this will workout better then multiple Cree + oval optics [tried that] IF you need short range illumination.

 

[VidPro]

if you run items like that below the 100ma spec , they should compare favorably to the output PER watt of a high-bright led, even a cree one.
but run at 80-100 they do not have the ability to remove enough heat, unless you tie the Legs down to something that will remove the heat.
and they will not run tens of thousands of hours at thier original output.
If you run them at a nice low, like 40ma they should work great and better by FAR than running 5mm's at an overdriven 40ma (even 4 die)

a star (high powered) item, run at something like 80-100ma runs rather cool, thanks to its heat sink. and would be more efficient again THAN these things. but the cost for that item would be much higher. there would be more avilable phosphors on a star item run at low, than a hard driven 10mm like this, so the star item would last with output for much longer, and MUCH longer still when driven lower.

If you use these things, leave the legs dangling out in the air, and put the legs onto a copper board (wide PCB foil path), or a metal rail, or SOME way to get the heat away from them, even containing the "front" in a dome light will reduce the heat removal from them. Ex: i turned an array on its face once, and it turned blue from heat, and basically ruined it. EX2: some directions for similar items say "dont clip the legs after assembling" EX3: running similar items when we heat sinked the legs they survived MUCH longer.
a simple copper fat guage wire, like 0-4 guage , is another cheap trick to remove the heat from its legs.

If your going to spend a lot of TIME assembling (time is money), and this item will need to RUN for a very long time, you would be better off with a "star" item, even a cheap star item. also star items are more durable, they can handle a bit of harsh drive for longer without croaking.

if your assembly time is experimenting and having fun, and they are not "area" lights needed to be on constantally, then they are certannly cheaper and will do the job, and relativly speaking the output will be relative, after all you have to be 5+TIMES as bright to look to human eyes to be 2 times brighter.

Multi die leds like these and the 5mm ones, are very efficent when run at lower currents, JUST like high powered leds are more efficent when run at lower currents. and the Chart thing shows that the efficency for multi die leds like this is very high WHEN run low.

that is my assessment.

 

[VegasF6]

Wok: Where did you get the clear lucite looking holder? That's pretty neat.

Vidpro: thanks for the good information there. I was wondering how you would heatsink dome leds. I may have to check around on prices for luxeon clones even, I dunno. (on stars)

Mostly I just want to play, and I was curious as to how these dome leds might compare. Potentially, it might turn into an area lighting project for the interior of my conversion van. I would like to install in various places and perhaps dim on a potentiometer. Some commercially availible solutions might be something like these 2 item's:
http://www.dealextreme.com/details.dx/sku.7556
http://www.dealextreme.com/details.dx/sku.3422
Too bad those don't give any idea of ouput or power consumed.

I kind of prefer an open air cooled solution, but you never know what the future may hold. What got me thinking was how the DX 22,000 MCD leds are over driven to heck and back and seem to hold up pretty good. If they have any sort of heatsink solution, I guess it could be the batteries them selves though, never thought of it that way before.

I guess if they ever did make it to my van, they could be on as long as 2 hours at a time.

 

[Wok]

VegasF6: I salvaged the holder from the tip someone had dumped a box of crayon holders....the bore fits the 10mm led flanges.They are 5 tube sections. Judging from VidPro's comments it may not be such a good idea to encase the led

VidPro: Thks for info. So far I have destroyed several Cree modules from track abuse [dirt tracks & bush bashing]....led abuse deaths haven't featured yet

I will retest @ 50mA & check if that will give sufficient light.

 

[VegasF6]

I think the holders are fine, just need to come up with two parralel aluminum tracks for the back side to tie the emitters two. Looks good anyhow!

 

[VidPro]

another thing we did to try and heat sinc the legs, was wired normally, with just small wire, then i poured epoxy over the whole thing, like a "ice block" as they call them things that are potted in full epoxy blocks.
while the epoxy doesnt get heat away quickly, it was down the entire length of the leg, so (the idea was) slowly but surely.
when we blocked the whole thing in epoxy, including the original dome, they had NO more optics at all, and about 180* type of output.

note, for all of the things i was trying it was for Area lighting, lighting the kitchen, and the van (work van which uses the lights for hours and hours). it was TIME that was the problem for us, 300-1000 hours they would work fine the way they were, but my intentions was to try and get it to last for infinity , ya thats it, infinity and beyond . . . :wave:

if the intention is to replace a candle, a HID or an Incan, well then not much would need to be done. if the intention was to try and get it to do the 100,000 hours (in thier dreams) or say 5-10k before its half dim, that was what we did that accomplished that. over TIME the star items still whooped them.