Critique our idea...

[blasterman]

The reduced frustration of LEDs on stars is definitely worth any extra expense

LukeA has a point. I can work with bare Cree or K2 emitters, but stars are certainly much easier to deal with...just more expensive. This is why you buy a couple first and get used to soldering. If you just can't deal with bare emitters, then obviously you have to spend the extra coupla bucks for stars.
　

I am now putting together my 3rd light driven just off a full wave bridge rectifier

Question on this (although I should have read prior threads). Negating the rectifier circuit for a moment, do you wire the 34 (or so) LEDs in one series with AC, or are they split x 2 (RMS)? I have a box of XR-Cs doing nothing and want to try this.

Yes those XR-Es would be super easy to use compared to my first choice. They even go to 107lm on the cooler colors at 350mA.

As per mentioned above, you want to avoid cool-white LEDs because you will seriously hate yourself when you see how cool the room light turns out to be. I prefer warm-white / neutral white alternating, while my brother prefers neutral white. I think part of my reason for not liking straight neutral white is they tend to vary a lot in terms of tint. Alternating them with warm-white evens things out.

I have power LEDs ranging from older 30/40 Lumen Crees to 400lumen Bridgelux, and the leap from 30-40lumen to 80-90lumen is HUGE when it comes to interior lighting. Nothing against Rebels, but you want AT LEAST XR-Es for this (or the newer Rebels). This cuts the number of LEDs you need to use ($$$) in half.

As a result you might feel slightly dizzy if you use too much LEDs in one area.

:thinking:
While bare LEDs on the ceiling are very specular in nature, multiple LEDs spaced half a foor apart or so aren't hard to live with. Plus, GSX said he's going to mount the light track near the side walls, which will produce a large amount of diffuse, wall reflected light in addition to the direct light on the ceiling. This is also why you build one light strip first and see how it looks. Personally my guess is it will look pretty cool, and I'm an ambient light kinda guy.

As far as I am aware of, MCE's are better used in such places like indoor lighting because the emitters are held closer together

MCEs have the benefit of tighter lighting density vs four LEDs, but don't look aethestically better than single LEDs, or have a functional advantage. They can also be more expensive and less efficient than four P4s.

Again, I go back to my Bridgelux which have more array emitters and a larger emission area than MCEs, and they are just as obnoxious when directly viewed as R2s. Bare, warm white P4s driven normally at about 80lumens are about the upper end (IMHO) before LEDs really get irritating to view directly. 150 lumen K2's would be blinding dead on, but tolerable if moved closer to the side walls.


　


　

 

[Illum]

LukeA has a point. I can work with bare Cree or K2 emitters, but stars are certainly much easier to deal with...just more expensive. This is why you buy a couple first and get used to soldering. If you just can't deal with bare emitters, then obviously you have to spend the extra coupla bucks for stars.

Not to mention the assurance that your not shorting to the heatsink:green:

MCEs have the benefit of tighter lighting density vs four LEDs, but don't look aethestically better than single LEDs, or have a functional advantage. They can also be more expensive and less efficient than four P4s.

well, I'd agree on that based on heatsinking alone...but I still like 'em anyway:nana:

 

[GSX-1300R]

Seems like you guys have been busy since I last logged in :D

I’m waiting for my things to get here in the mail that were ordered yesterday and Friday. I'm getting anxious already lol.

On painting the aluminum bar, am I only supposed to paint one side of it and leave the other side bare? My thought was to lightly paint the whole bar with the exception of where the LEDs were going to be attached.

 

[LukeA]

On painting the aluminum bar, am I only supposed to paint one side of it and leave the other side bare? My thought was to lightly paint the whole bar with the exception of where the LEDs were going to be attached.

That's fine!

 

[GSX-1300R]

I should be able to start posting project photos this week. I think I got a lot of information from the members that posted replies in this thread. I hopefully didn't bore anyone with my noobish questions.

One day guys, one day I won't be a noob anymore :crackup:

 

[GSX-1300R]

Alrighty then... I just opened my package from FutureElectronics for those 5 Rebels I bought on Friday. I opened the box and pulled out the bubblewrap and saw the bag and it looked empty! I was like :thinking:

My wife was like "where are they?" lol. Turned over the ESD bag and they were under the sticker. I was like HOLY S*** those are TINY!!! I have soldered a lot of things but nothing of this size, all I can say is WOW.

So after the initial shock and awe, I was curious on how hot the little Rebels get? To me those little guys shouldn't be able to get that hot, but I'm sure that they could though.

How do you all use something that small in projects? How do you all solder something that small? I can see why you guys suggested the XR-E stars to us (can't wait till they get here!)

 

[Illum]

How do you all use something that small in projects?

depending on how big your project is....
I don't know of anyone using the rebel in fixed lighting applications but I have seen them used in modding flashlights, specifically koala's EM-T towers, the only LED retrofit in existence for surefire E series
Surefire E-Series MicroTower (E-MT) LED drop in

How do you all solder something that small?

While there is a number of ways to solder SMT components [such as hot air gun, heat gun + solder paste, etc], Brlux's concept should get you started on some ideas :whistle:
How to Solder SMT with a toster oven (Luxeon Rebel)

a couple more ideas on soldering and heatsinking home soldered rebels
http://www.candlepowerforums.com/vb/showthread.php?t=220846
http://www.candlepowerforums.com/vb/showthread.php?t=174009

for info on these little gems, be sure to review Evan's thread
100 Lumen Rebel technical evaluation
Rebel Current/voltage data

cheers:huh:

 

[GSX-1300R]

Thanks Illum for the info on the Rebels. I actually got some of the XR-E stars, so the Rebels are going to be sitting until I need them for something else.

My 1/8th x 1.5" x 5' aluminum bar came in today, so I got it prepped and painted. I only have 5 stars to be mounted on the bar at this time. There's room for two more on the bar but I couldn't get them in the photo from our camera phone. :thumbsdow

On powering these stars I was looking at the 12w 350mA Off-Line Driver by Xitanium. I was curious if the 12w driver would be able to handle seven stars in series instead of my original five.

 

[LukeA]

On powering these stars I was looking at the 12w 350mA Off-Line Driver by Xitanium. I was curious if the 12w driver would be able to handle seven stars in series instead of my original five.

It can handle up to eight 1W LEDs so seven will be fine.

 

[Illum]

On powering these stars I was looking at the 12w 350mA Off-Line Driver by Xitanium. I was curious if the 12w driver would be able to handle seven stars in series instead of my original five.

the Xitanium 12W driver has a voltage output at 32.6V max and is capable of driving up to 8 LEDs [LED-120A-0350C-33F], now the 700ma modules [LED-120A-0700C-24F] only go up to 24.6V so they are only good for up to 6 in series max.

Xitanium Driver Technical Data Sheet & Wiring Diagrams

You have the option of using 12LEDs in series parallel configuration [6S2P] for each LED to receive 350ma. While the diagram sounds simple take note that since each LED's Vf is slightly different, even when its in own bin or type, that one string may consume more current than the other. This will cause:
Uneven lighting if its all wired as one row
Uneven degradation of your LEDs [the unfortunate string that eats current the most ages faster]
Uneven cooling

One way to compensate for this hazard is the "current mirror circuit" which uses thermally connected transistors to even out the current to each string.
For details, reference LED magazine[DESIGN FORUM: Avoiding thermal runaway when driving multiple LED strings] [February 2009 Design Note]

the BD139 mentioned here is listed under Fairchild Semiconductor - NPN Epitaxial Silicon Transistor
Datasheet here
Availability: Mouser, Jameco