5mm Flat Wide Angle COLOR led HELP requested

[Jase]

Very first post here, I'll try to get all the terms correct. Please bear with me. Been lurking for almost a year now. I'm a hobbist and leds are used alot in my hobby so I try to stay up on the tech as much as possible.

First, yes I'm a new to l.e.d.s. I've been trying to search and figure out all the terms and how these led are made, how they work etc. But I'm having some problems with how to compare one product to another without having them infront of me. It seems you can clam anything about an led online when your selling them.

So it led me here. I haven't seen alot of talk about colored 5mm leds here on the board but I have read some discussions and what I've seen leads me to believe you guys know what your talking about.

Let me please tell you all what I'm looking for.

-5mm Color Emitting Leds.
-Clear not colored epoxy because the colored epoxy will filter out some light and I need these to be as bright as possible. (prob didn't need to add that)
-RED to start, lets work out the best red leds first -then other colors to focus this request alittle. A company that makes a good red will prob good for other colors and give me a place to start.
-Flat Top, Inverted Cone or "Straw Hat" type 5mm leds with as wide angle as possible.

** these leds will be set in a string/ladder of leds front to back in a row or end to end. A lot of the light will be going into the back of the next led so I need as wide angle as possible. They kinda have to be this way for the fitment into a long tube to light it up.**

I would like them to run off the 20-25ma standard but I'll probably overdrive them to around 35ma. That being said if any of you know any that run off higher current with crazy brightness let me know just keep it <100ma please.

I'd much prefer the 20-25ma leds so I can tightly stack them like in the pic, if I use the 100ma ones I'll be restricted to only 45 of them and spacing them out might give me a corn on the cob effect along a 36 inch tube. (unless they are really insane then I might be able to work something out)

I hope I have given enough info to get some advice from you guys
If I used any terms incorrectly or you need some more info let me know please.

Also please include the name of the L.E.D. company, and even the product code would rock.

Thanks so much guys!

FYI, I did see there is another thread about Red vs Orange leds, good info on brightness and wavelengths etc but not alot on Mcd or where to buy or quality.

 

[JohnR66]

I'm impressed with Cree's (www.cree.com) 5mm color LEDs. They're the brightest I've seen and of good consistent quality. Check their website for the part number's you need. I bought mine from DigiKey.

Connecting them in parallel like this may pose some problems. Slight variance in forward voltage of each LED could cause one to "hog" more current and can burn it out or at least cause brightness to be uneven. You should check each LED before soldering it up. Even then Vf could drift over time. If supply voltage is high enough, I'd string them in series.

Second problem is heat. There is no where for the heat to be dissipated in this arrangement. I'd not drive over 20ma (amber/red) or 15 ma (blue/green).

This project is better served using high brightness surface mount LEDs. Not sure of the best LEDs here though.

 

[Jase]

Good pionts all and thank you for replying.

Let me go into detail about why this is going to be set up in the fashion I showed in the pic.

Slight variance in forward voltage of each LED could cause one to "hog" more current and can burn it out or at least cause brightness to be uneven. You should check each LED before soldering it up. Even then Vf could drift over time. If supply voltage is high enough, I'd string them in series.

As of now I'm going to running this off a battery pack (7.2 li-ion @ 2600ma) so they really have to be run in parrallel as far as I can tell. Actually they'll be run in parrallel and series- 3 running around 2.2v etc etc.

To be honest I don't know enough about what you mean by variances in forward voltage (Vf right) or why one L.E.D. would hog more current and burn out... if you could explain it in laymans terms that would be great but if it's to complicated that's cool, I'll look into on my own also.

-- I thought that the current would be spread evenly over all the leds equally in parrellel... I've seen this done in my hobby alot and even have a couple of led ladders in projects already that seem to work well (they do have alot of diffusion (which I'm trying to cut back on to increase brightness). But what your saying does make sense to me in my head so I'll have to look this up, thanks for telling about this.

--Come to think of it i did have a couple leds burn out on one try but I wrote them off to poor quality of the Chinese leds. Now I wonder...

Second problem is heat. There is no where for the heat to be dissipated in this arrangement. I'd not drive over 20ma (amber/red) or 15 ma (blue/green).

Haven't had a problem yet with this, but I have been toying with the idea of a tiny fan at the bottom of the tube to push air through the tube to help. I know it wouldn't to a great deal but kinda outta options.

This project is better served using high brightness surface mount LEDs. Not sure of the best LEDs here though.

I would love to use surface mounts. I have been researching the idea of haveing long thin pcb board(s) made for this project like seen on ebay and everywhere else but the thing is that this is going to be placed inside of a 1" dia tube and needs to be visible 360 degrees around. Even if I had them placed on both sides of the pcb there will most likely be dark lines down the tube... hope that was clear.

Cree seems to be a good company I've been to there website alot, not very userfriendly but it works. Only I can't seem to find anything from Cree in Red that is over 30 degrees (has to be at least 45 for this to work)

Surface mounts also use alot more current don't they? The ones i've been looking into seem to. And I'd have to use twice as many of them (one on each side of the pcb etc etc just don't think it will work for a battery powered project.