# please help me select an LED



## RustyShackleford1 (Feb 6, 2015)

I am trying to do a project with LED landscape lighting, starting from scratch with emitters, and need help selecting the right part. Here are my requirements:

1. Low color temperature (2700 or less), and high CRI (mainly, I don't want the yucky green tint so common to cheap "warm white" LED bulbs).
2. Forward voltage of 3v or less.
3. Lumen output in the 100 range (or a bit less) when driven at "nominal" current in the 300ma range.
4. Possible to hand-solder.

I suspect a Cree product is the one I'd want, but they have so many products that I'm a bit overhwelmed. Also, they look like they're gonna be no picnic to solder by hand; I do have reasonable skills, some 3.0 reading glasses, and a decent solder station.

Thanks.


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## Anders Hoveland (Feb 7, 2015)

Not many manufacturers make 2700K in a high CRI version. For high CRI, it's usually 3000K, or sometimes higher.

Osram Opto LCW CQ7P.CC-JUKQ-5U8X-1-K 95CRI 2700K emitter 3.2v


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## RustyShackleford1 (Feb 7, 2015)

Sorry, I didn't mean a 95 CRI. Actually, I'm not sure what CRI I need. It's not like it's gonna be inside illuminating fine artwork. Mainly, I don't want that yucky green tint that a lot of cheap-o "warm white" LEDs seem to have. But I do want a nice warm color.

It seems like maybe the Cree XP-E2 or XP-G2 is the ticket, but they seem pretty similar. Thoughts ?


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## Anders Hoveland (Feb 7, 2015)

RustyShackleford1 said:


> Actually, I'm not sure what CRI I need. It's not like it's gonna be inside illuminating fine artwork. Mainly, I don't want that yucky green tint that a lot of cheap-o "warm white" LEDs seem to have. But I do want a nice warm color.


An 80CRI 2700K LED has an okay _color_ of light. The light is just a little unnaturally orange, and simultaneously a little purplish-tinted, but this should not matter if it is just for outside lighting (I find the light a little too eerie for indoor use though). The color rendering is _okay,_ but really not the best. Red colors appear very dull, skin tones appear a little yellowish grey and dead, and green leaves appear a little yellowish and sickly. I mean, it's okay, it works, but may not be something you want to use to display your landscape. 

Probably what you would be looking for is 85-92CRI.


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## Anders Hoveland (Feb 8, 2015)

I was walking at night through the neighborhood, and I happened to see some landscape lights in the front of someone's house. They were just little lights, with glass flower petals facing down. They looked really nice, and I looked under them just to see if there were little halogen capsule bulbs under the petals. They were LED! Hard to say exactly, but seemed like 3200K, maybe around ~90cri (though difficult to really know exactly). The color of light was crisp and "bright", but still had a nice warm feeling. Some of the lights were over some red flowers, and everything seemed perfectly colorful, the leaves a deep green and the red vibrant.

I am a little skeptical of LED lighting, but these things are certainly something I would get. 
This same house had two of a different type of LED landscape flood light fixture also, maybe 85cri, and there was a clear difference between these larger lights and the other little LED lights, in terms of color rendering on the green plants.


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## nickelflipper (Feb 8, 2015)

This is pic of some green foliage with the Cree XM-L2, S6 7D3 90+CRI (2900K) that Illum used to carry. Bare emitter, at a guesstimate of 350+ lumens.


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## RustyShackleford1 (Feb 8, 2015)

I guess I just have to buy a few and see how they look. I always had it in my head that I want 2700, maybe lower. Worst is that Mouser doesn't sell that many different versions in quantities less than 110 or 480. Is there any vendor better for getting onesies ? Perhaps I get somebody to send me an assortment of free samples !

And then I have to figure out how to solder leads to the damn things - but there seems to be a lot of info on that here.


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## Anders Hoveland (Feb 8, 2015)

RustyShackleford1 said:


> And then I have to figure out how to solder leads to the damn things - but there seems to be a lot of info on that here.


With 3W cree chips, that can be challenging. It takes good eyesight and precision hand-eye coordination. And a little practice to get it right. 

A cree chip may only be 3.2mm wide. Just to put things in perspective, that's only 5000 times what the wavelength of red light is. And the leads are even smaller. You just can't put a big dab of solder on it, because it would short-circuit across the leads. It's definitely possible to do (I was able to figure out how to do it), but I really do not think it's the type of thing that _everyone_ could do. You might even want to consider getting someone else in this forum to do it for you, if you are not the type of person able to figure things out or do not have good eyesight.


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## RustyShackleford1 (Feb 8, 2015)

Anders Hoveland said:


> With 3W cree chips, that can be challenging ...


Thanks, Anders, I think I'm looking at 1W chips, at least the "nominal" current (350ma at a 3v forward drop); but of course the maximum allowable forward current is about 3X that.

I guess I'll just have to buy a couple and try my hand at the soldering, but it sounds discouraging.

P.S. I think you might be off by a few zeroes on your comparison to red light !


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## DIWdiver (Feb 8, 2015)

Yeah, wavelength of red light is around 650 nM, five times that is 3250 nm or 3.2 um. So it's not 5 times, it's 5000 times.

I'd recommend that if you are going to buy bare emitters, it's probably best to also buy some bare stars and learn one of the DIY reflow techniques. Even a 1W LED needs some heatsink if it's going to run at 1W, and you pretty much have to reflow it onto the heatsink. Might as well just do it right.


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## RustyShackleford1 (Feb 9, 2015)

DIWdiver said:


> ... buy some bare stars and learn one of the DIY reflow techniques.


Can you give me a link or two to get me started on this ? Thanks !


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## Steve K (Feb 9, 2015)

a search ought to pull up a lot of hits. YouTube has more than a few...
https://www.youtube.com/watch?v=l0IbGDyeHZ4

this matches (roughly) my method for just heating the star with a soldering iron and letting the solder melt and attach to the LED.

In the video link above, the fellow blows on the LED and star just after pulling the soldering iron off of it. I was a bit worried that he might blow the LED off of the star, since the star has a significant thermal mass and the solder stays liquid for a while.


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## RustyShackleford1 (Feb 9, 2015)

RustyShackleford1 said:


> Can you give me a link or two to get me started on this ? Thanks !


The video is helpful, but I can't seem to find anyone who sells the bare stars (without an LED already attached). Or maybe I'm better off getting ones WITH the LED attached, except you don't really know EXACTLY which LED you are getting. For example:

http://www.ebay.com/itm/10pcs-lot-U...-3000K-Led-Emitter-on-16mm-Star-/261581302157

... says it's an XP-G with color temp between 2900-3000; but no clue about CRI.

Also, I wonder what is the thermal performance of a 16mm or 20mm star, i.e. how much juice can I put through it and have the LED survive long-term, without any additional heatsink ?


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## thslw8jg (Feb 9, 2015)

Try illumn for bare mcpcb's


Sent from my iPhone using Candlepowerforums


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## DIWdiver (Feb 10, 2015)

For 1W LEDs, any old star should be fine. I have 10W LEDs running on 16mm aluminum stars with no issues. www.dealextreme.com and www.kaidomain.com have some really cheap. But beware, those that say they will fit many different LEDs probably don't. You want one that specifically says it will take the LED you want to use. Kaidomain seems to be better about saying which one they are for.


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## Steve K (Feb 10, 2015)

RustyShackleford1 said:


> The video is helpful, but I can't seem to find anyone who sells the bare stars (without an LED already attached). Or maybe I'm better off getting ones WITH the LED attached, except you don't really know EXACTLY which LED you are getting. For example:
> 
> http://www.ebay.com/itm/10pcs-lot-U...-3000K-Led-Emitter-on-16mm-Star-/261581302157
> 
> ...



my tendency is to go to some of the general electronics mailorder places, such as digikey.com or mouser.com 
You can get very specific about the LED and the star, but by the same token, you have to be familiar enough with the stuff to know what you are buying.

The stars will have a proper datasheet available on their web site, so you can see what the thermal characteristics are. In most or all uses, the stars are intended to be a thermal interface between the LED and a heatsink, and not serve as a heatsink itself.

amusing anecdote: on my last such order from Mouser, the bare stars came in an ESD black cardboard box with anti-static foam in it. A MCPCB is that last thing that would be sensitive to ESD, so I thought it was a bit funny. It might just be a reflex for them to ship any star in an ESD container, regardless of whether it has an LED on it or not?


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## RustyShackleford1 (Feb 10, 2015)

Steve K said:


> ... as digikey.com or mouser.com
> You can get very specific about the LED and the star


Yes, I like Mouser, but didn't realize they sell stars. They seem very specific about ones being for specific Cree models. But unfortunately those seem to be only 20mm, which I think the 16mm will work a lot better for me



> The stars will have a proper datasheet available on their web site, so you can see what the thermal characteristics are. In most or all uses, the stars are intended to be a thermal interface between the LED and a heatsink, and not serve as a heatsink itself.


They have thermai conductivity (W/m-K) but I'm not sure how to go from that to degrees-C per watt. Anyhow, DIWdiver seems encouraging that I'd be ok wiht 1 watt on a 16mm star and no additional heatsink.




> the bare stars came in an ESD black cardboard box with anti-static foam in it


Yeah, over-packaging seems like a weird kind of passive-aggressive thing with some vendors (not talking electronic, specifically).


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## RustyShackleford1 (Feb 10, 2015)

Speaking of which, does anyone know of a place besides Mouser to get one'sies of Cree LEDs - not just a few of them, but the full range of binning ? Mouser has some, but especially not the 2200-degree ones that I'd like to try out.


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## DIWdiver (Feb 10, 2015)

RustyShackleford1 said:


> Anyhow, DIWdiver seems encouraging that I'd be ok wiht 1 watt on a 16mm star and no additional heatsink.



Woah! That isn't what I meant. It could be true, but...

If the star is hanging out in the air, both sides exposed, it's enough. But mount it to the inside wall of a little plastic box, and you could be in trouble. You should have at least some thermal path to the outside.

What I actually meant is that _in your case_ any old star, any size, is enough to get the heat from the LED to the heatsink.


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## RustyShackleford1 (Feb 11, 2015)

DIWdiver said:


> Woah! That isn't what I meant. It could be true, but...
> 
> If the star is hanging out in the air, both sides exposed, it's enough. But mount it to the inside wall of a little plastic box, and you could be in trouble. You should have at least some thermal path to the outside.
> 
> What I actually meant is that _in your case_ any old star, any size, is enough to get the heat from the LED to the heatsink.


Oh, sorry to have mis-represented your representations. But even with the additional caveats, I'm optimistic. The LED+star are going to be epoxy'ed at right angles to a little piece of circuit board, which will be fashioned into a miniature-wedge "bulb". So that's pretty close to "both sides hanging out in the air exposed". And landscape-lighting fixtures are pretty "open" (we're definitely not talking "inside a little plastic box"). But thanks for clarifying.


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## RustyShackleford1 (Feb 11, 2015)

Starting to wonder if the MX6 LEDs might be better for me:

http://www.cree.com/LED-Components-and-Modules/Products/XLamp/Discrete-Directional/XLamp-MX6

They are 5-6mm square and have electrodes along both sides. Still, there's the issue of exactly what to solder them to, to get enough heat dissipation.

I continue to be overwhelmed at all the different families of Cree LEDs, and trying to figure which is best for my requirements of reasonable quality very warm white light and forward voltage of 3v or so. Another is being able to obtain one-sies for my experiments, which is how I came across the MX6 (only 2200 degree bulb that Mouser sells 1 at a time). Not that I'm sure I need 2200, but I'd certainly like to experiment with it.


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## gofastman (Feb 11, 2015)

RustyShackleford1 said:


> I am trying to do a project with LED landscape lighting, starting from scratch with emitters, and need help selecting the right part. Here are my requirements:
> 
> 1. Low color temperature (2700 or less), and high CRI (mainly, I don't want the yucky green tint so common to cheap "warm white" LED bulbs).
> 2. Forward voltage of 3v or less.
> ...



It doesn't fit requirement 1, but perhaps a Nichia 219B should be a consideration. It has the most perfect tint I have seen! minumum CRI 92, 4500k, perfectly neutral white light.
if you are dead set on a warm, incandescent-like tint, consider the Cree XP-G2 Q2 7C4

I stole this pic from lithium466:





Nichia 219B on the left, Cree on the right.


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## RustyShackleford1 (Feb 11, 2015)

gofastman said:


> if you are dead set on a warm, incandescent-like tint, consider the Cree XP-G2 Q2 7C4


Thanks. I can't quite locate the Q2 7C4 in the inscrutable binning document, but just narrowing it down to the XP-G2 family helps a lot.


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## WeLight (Feb 11, 2015)

Anders Hoveland said:


> Not many manufacturers make 2700K in a high CRI version. For high CRI, it's usually 3000K, or sometimes higher.
> 
> Osram Opto LCW CQ7P.CC-JUKQ-5U8X-1-K 95CRI 2700K emitter 3.2v


Actually a lot of manufacturers make HI CRI leds


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## WeLight (Feb 11, 2015)

Steve K said:


> a search ought to pull up a lot of hits. YouTube has more than a few...
> https://www.youtube.com/watch?v=l0IbGDyeHZ4
> 
> this matches (roughly) my method for just heating the star with a soldering iron and letting the solder melt and attach to the LED.
> ...


Ouch that was painful to watch, buy a tube of solder paste and use your toaster oven,


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## nickelflipper (Feb 11, 2015)

RustyShackleford1 said:


> Oh, sorry to have mis-represented your representations. But even with the additional caveats, I'm optimistic. The LED+star are going to be epoxy'ed at right angles to a little piece of circuit board, which will be fashioned into a miniature-wedge "bulb". So that's pretty close to "both sides hanging out in the air exposed". And landscape-lighting fixtures are pretty "open" (we're definitely not talking "inside a little plastic box"). But thanks for clarifying.


Sniff...sniff.. if your experiment with the led stars goes up in smoke, then try the direct thermal path stars like Sinkpad or Noctigon (and a chunk of aluminum?). Vob sells the Sinkpads in the cpfmarketplace/WTS flashlight parts.


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## RustyShackleford1 (Feb 12, 2015)

nickelflipper said:


> Sniff...sniff.. if your experiment with the led stars goes up in smoke, then try the direct thermal path stars like Sinkpad or Noctigon (and a chunk of aluminum?). Vob sells the Sinkpads in the cpfmarketplace/WTS flashlight parts.


Oh yeah, those look cool (pun ...). I sure wish I could buy stars with LEDs attached, but for some reason, all those are with REALLY high-CCT emitters. Well, a few in the high-3000s, but I don't consider that "warm white" (I am trying to emulate dimmed incandescent). Toaster oven ? Hmm, maybe, if I can find some really low-temp solder paste and if I don't mind a little lead in my toasted cheese ...


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## gofastman (Feb 12, 2015)

Mtnelectronics has the Cree 90+ CRI mounted and ready to go


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## FRITZHID (Feb 12, 2015)

A heat gun works well for reflowing LEDs, solder paste helps even more, just try to make sure you use a noclean paste/flux OR make sure you clean the excess flux off very well.


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## DIWdiver (Feb 12, 2015)

RustyShackleford1 said:


> Oh yeah, those look cool (pun ...). I sure wish I could buy stars with LEDs attached, but for some reason, all those are with REALLY high-CCT emitters. Well, a few in the high-3000s, but I don't consider that "warm white" (I am trying to emulate dimmed incandescent). Toaster oven ? Hmm, maybe, if I can find some really low-temp solder paste and if I don't mind a little lead in my toasted cheese ...



Please don't put lead-based solder in an appliance used for food. Lead evaporates when molten, and will get into your appliance, and from there into your food. I doubt fluxes would be good to eat either.

People do use toaster ovens for reflowing, but they are strictly for that, not for food.


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## nickelflipper (Feb 12, 2015)

I use Kester ep256 and a hotplate found at the thrift shop for reflowing.


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## RustyShackleford1 (Feb 12, 2015)

Thanks for the mtnelectronics pointer (have been in contact, VERY helpful folks). Still, the warmest they have is 2900, but that might do for the time being.

On re-flowing, have no fear, I have the sense not to mix it with food preparation, and thanks in particular for the solder-paste rec.


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## RustyShackleford1 (Aug 25, 2015)

RustyShackleford1 said:


> Starting to wonder if the MX6 LEDs might be better for me ...
> 
> They are 5-6mm square and have electrodes along both sides. Still, there's the issue of exactly what to solder them to, to get enough heat dissipation.


So I've been messing with these Cree MX-6 emitters and I really like them. No one seems to sell MCPCB stars for the them though. Any thoughts about how to provide them with some heat-sinking and connection points ?


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## WeLight (Aug 25, 2015)

If you want lower CCT. Cree have 2200k available in several platforms like XT/XP, XPG-2 is available in min 90 CRI, on stars as is 2200k, but you will have to PM me for details


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## RustyShackleford1 (Aug 26, 2015)

WeLight said:


> If you want lower CCT. Cree have 2200k available in several platforms like XT/XP, XPG-2 is available in min 90 CRI, on stars as is 2200k, but you will have to PM me for details


Having trouble PM'ing you ... I got the MX6 because it's the only 2200 emitter that Mouser had in-stock (in small quantities, at least). Are you saying YOU could supply me with 2200 LEDs mounted on stars ?


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## SemiMan (Aug 26, 2015)

RustyShackleford1 said:


> Having trouble PM'ing you ... I got the MX6 because it's the only 2200 emitter that Mouser had in-stock (in small quantities, at least). Are you saying YOU could supply me with 2200 LEDs mounted on stars ?



Digikey has 2200K Lumileds in stock, lots of them, as well as tight matching 2700, 3000K high CRI in a few families.


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## WeLight (Aug 26, 2015)

thats what Im saying


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