DIY LEDs - The write-up

[der_wille_zur_macht]

A dumb question....are people still using the XRE Q5's or have people switched to the XPG's.....Is there any advantage to going with the XPG's?

The XP-G is still somewhat price/availability limited. If you can find them for close to $6 each, I think it makes sense to use them. They're about 30% more efficient than XR-E but have a wider viewing angle, which needs to be kept in mind.

Thanks!
I don't know how high I'm gonna hang the light. How deep can I keep my SPS if I'm gonna go with 48 LEDs, 60 degree optics?

It's really hard to generalize but I'd say top to bottom if conditions are good otherwise.

 

[chriscobb]

I seen them on a site from a place not to far, but don't really know the specs or what since I see several different ones listed......

 

[chriscobb]

This is the link to where I found the XPG's http://www.arrownac.com/manufacturers/cree/xlamp-leds.html

 

[der_wille_zur_macht]

It depends on the bin number. At 350mA, Q5 bin is 107 - 114 lm per watt. The most common "high" bins for the XP-G seem to be R4 and R5, which are 130 - 139 and 139 - 148 lm/w, respectively.

It's also worth noting that the XP-Gs tend to drop about 10% less voltage at a given drive current, which means (in theory) you can fit 10% more of them on a given driver.

 

[cnbridge]

http://hackaday.com/2010/01/29/salty-leds/

I have been following this thread on another site and the person who built this fixture has posted the Arduino code on google (wasn't sure if I could post the link) as well as instructions on building a led controller. It controls sunrise, sunset and moonlight function for about $60. Can this be applied to parts that could be purchased in the US? I am not good with electronics so I am not sure.

 

[widmer]

Question:

So I had to replace my laptop charger because the plug fell apart on my old one. I figured that my old one (rated 20V, 2A) would make a good power supply for a little refugium light with a buck puck and 4 or 5 of the XR-E's. But when I snipped the cord and hooked it up to my multimeter, it only registered like 0.6 amps. Is this because it's not under load? Is it OK to use a laptop charger to begin with, or should I go a different direction?

Thanks

 

[der_wille_zur_macht]

How were you trying to measure current? There shouldn't be ANY current without a load on the power supply.

Most power supplies list a max current, so check it out. In general there should be no problem using a laptop charger. I've used one on one of my prototype builds for a few months with no issues - they're probably better regulated than we need in this application.

 

[widmer]

Related question: I am going to try the whole drilling and tapping thing for fun when I do my sump light. So:

A) Which thermal paste are you guys using? Think it would be ok to do the two-dollar ebay stuff or should I go with a name brand?

B) Are nylon washers necessary when tightenting the screws down onto the LED or is metal fine? It looks like I should be fine with metal providing that I keep it clear of the terminals, but I can picture the potential benefit of having the nonrigid nylon..

 

[der_wille_zur_macht]

I've used Radio Shack brand stuff on my proto builds. If you apply it correctly (sparingly) and the surfaces are nice, any old brand is probably better than a poor job or a thick adhesive.

Personally, I would NOT want to attempt screwing stars down without the nylon washers - the screw heads on even the smallest suitable screws are pretty bulky, and shorting an LED to a heatsink is no fun. Though, many of my proto builds have used 3-up Rebels, which have a lot less "empty" space on them than a typical Cree star.

 

[Neogenocide]

Related question: I am going to try the whole drilling and tapping thing for fun when I do my sump light. So:

A) Which thermal paste are you guys using? Think it would be ok to do the two-dollar ebay stuff or should I go with a name brand?

B) Are nylon washers necessary when tightenting the screws down onto the LED or is metal fine? It looks like I should be fine with metal providing that I keep it clear of the terminals, but I can picture the potential benefit of having the nonrigid nylon..

I also would not think of screwing them down without using nylon washers. My problem around here was finding them small enough.

Scott

 

[widmer]

How were you trying to measure current? There shouldn't be ANY current without a load on the power supply.

Most power supplies list a max current, so check it out. In general there should be no problem using a laptop charger. I've used one on one of my prototype builds for a few months with no issues - they're probably better regulated than we need in this application.

OOPS :hmm2: I was kind of worried after the fact that it wasn't under load when I tested it. Maybe it pulled the same maneuver as my mpja power supply when I hooked that thing up with a capacitor across the terminals and it detected the "short"? Either way, when I switched the multimeter back to voltage measuring, it read 20.3 volts so hopefully I didn't ruin it..

Thanks for the advice, I suppose I would maybe encourage others to use laptop power supplies then because the replacement I got was like 8 dollars on ebay and is rated at 20V 2A. Great to power a sump light...

Although I wonder if buck pucks are going out of style here as a meanwell which can drive 12 LEDs can be had these days for $26 with a group buy...

 

[Skeptic_07]

Does anyone know if XPE optics will fit correctly on XPG?

I didn't even think about this before I ordered the LEDs. :hmm2: Good thing I didn't order any optics yet.

 

[nitjt]

I got in a group buy at nano-reef for some meanwell eln 60-48D for 26 bucks and XPG at $5.30 per star. I pulled the trigger and got 48 cool white and 7 drivers so I will give an array a shot. With the XPG can I drive 13-14 leds with the meanwell? How many total LEDs should I use to cover a 48"x24" bowfont tank? I have a mixed reef with clams on the sand its about 29" deep. I now use two 250W HQI with Lumatek dimmable 400W ballast set at 275W with four 39W T-5 for actinic that I want replace with this array.

 

[Skeptic_07]

With the XPG can I drive 13-14 leds with the meanwell?

you might be able to. IIRC XPG has a lower forward voltage than XPE. They run at 3.3v when you're powering them at 1000ma and 48/3.3 = ~14.6 so you can safely run 14 on each driver.

 

[bstohrer]

I also would not think of screwing them down without using nylon washers. My problem around here was finding them small enough.

Scott

Try smallparts.com. I ordered from them through Amazon (free shipping over $25). A pack of 100 was a little over 2 bucks!

 

[Skeptic_07]

I was chatting with someone over on the DA forums who used meanwell drivers for his project. He was saying that the voltage pot is actually like a safety feature for running parallel strings. I'm not sure if this was correct so i wanted to ask it here. Please correct me if I am wrong. Basically you turn the current pot all the way down and hookup everything including the dimming control which should be cranked to the max. Using a multimeter, monitor the current as you increase the current bringing it up close to 1000ma, the rated maximum current for these LEDs. Then you decrease the voltage pot until you start to see the current start to decrease and stop. This way if you have an LED fail on one string, the other one cannot be overpowered. Is this really correct? Seems like this is wrong to me but I don't know anything about electronics.

edit: talking about eln-60-48D here

 

[kcress]

Skeptic; If I followed you correctly, yes, that sounds like the proper setup.

 

[laverda]

Kcress It that is true how many parallel strings of LEDs could you reliably run on one Meanwell? Even if it was just two it would save substantial cost on a large system. If it was 4 it would would also make controlling with an Aquacontroller much easier for me.

 

[skippyreef]

Anyone thought of using high power UV emitters in the 365nm range?

 

[chriscobb]

Thanks for the info DWZM!!!!!