DIY LEDs - The write-up

[nieves]

Has anyone heard of this particular LED -an SSC P7 C-Bin LED Emitter with 21mm Heat Sink Base-- which puts out up to 900 lumens. This one in particular? I think it's fairly new technology, and I was wondering if you (Soundwave) heard of this one when you first started creating your LED fixture, and if you did, why you did not go with this stronger LED.

http://www.dealextreme.com/details.dx/sku.12721

Awesome and informative thread!!!

 

[der_wille_zur_macht]

Efficiency (lumens/watt) is more important than absolute brightness, and in that regard, the P7 is average among good HP LEDs. The disadvantage is that it's basically 4 XR-E in a single package, which means you're getting 4 LEDs worth of light from ONE point source - it would be hard to build a fixture of the correct intensity with those LEDs and not have the spotlight effect. Using XR-E or Rebels instead allows you to create a more even distribution of light.

Also, when you look at the price, it's roughly comparable to an equal number of (more efficient) lower-output LEDs.

Plus, the C bin they're selling isn't the highest bin, so you're not getting 900lm from it unless it's dangerously overdriven.

 

[pookstreet]

With a tank that big, I'd probably get ~6 Rebels (they have a wider field of view than XR-E) in your favorite color, and run them on a dimmable 350mA buckpuck. You'll need a DC power supply to run the buckpuck - a 500mA or greater 24v wall wart would work. At these low currents, you don't need a fan if the heatsinks are big enough, especially since you'll be spreading the LEDs out apart from eachother. You could use PC processor heatsinks. No worries about having the LEDs enclosed - they're better off with good ventilation. Use an acrylic splash shield to protect them from spray from the tank.



On this tank I'd probably either do three buckpucks (for 18 LEDs) or two Meanwells (for 24 LEDs). I'd do dimmable 700mA or 500mA for a drive current. When you have fish in the tank, might as well run lower light or only one string. With corals, you can use the dimmers to simulate the correct lighting for the particular corals.

Any suggested source or sources to get these components? And once I get them, what do I do with them??? :lol:

Just curious, if I built the moonlights to be dimmable, would I be able to use the Apex controller to put them on a dimming cycle? Thanks.

 

[nieves]

The disadvantage is that it's basically 4 XR-E in a single package, which means you're getting 4 LEDs worth of light from ONE point source - it would be hard to build a fixture of the correct intensity with those LEDs and not have the spotlight effect.

Well, according to one review, they saw a near 180 degree dispersal of the light, so it's possible it's not going to get a spotlight effect. We might just go ahead and order one and see how much of a spotlight effect we end up with. At least I'd just be out $15

If we can get away with using less of these (of course assuming we don't see the "spotlight" effect), and get the same output, we'd be saving anyway.

Thanks for the quick response, too :lolspin:

 

[der_wille_zur_macht]

Any suggested source or sources to get these components? And once I get them, what do I do with them??? :lol:

Just curious, if I built the moonlights to be dimmable, would I be able to use the Apex controller to put them on a dimming cycle? Thanks.

Typical sources: ETG, dealextreme, ledsupply. Shop a bit to find the best prices. mpja.com for DC power supplies if you go with buckpucks.

If you get a dimmable driver that can do 0-10v DC analog dimming, you can use the Apex's 0-10V channel(s) to dim based on whatever programming you can dream up. The meanwell drivers come in a 0-10V DC dimmable flavor. The buckpucks come in a 0-5V DC dimmable flavor, so you could probably fake it by only using half the signal width from the Apex.

 

[der_wille_zur_macht]

Well, according to one review, they saw a near 180 degree dispersal of the light, so it's possible it's not going to get a spotlight effect. We might just go ahead and order one and see how much of a spotlight effect we end up with. At least I'd just be out $15

If we can get away with using less of these (of course assuming we don't see the "spotlight" effect), and get the same output, we'd be saving anyway.

Thanks for the quick response, too :lolspin:

According to the datasheet, available here:

http://www.acriche.com/en/product/prd/zpowerLEDp7.asp

They have a 130 degree viewing angle. That's about the same as Luxeon Rebels (135 iirc) and a little wider than XR-E (90 degrees iirc). I've never used a P7, but I have used 3-up Rebels, which is nearly the same thing (three Rebels mounted on one star) so I CAN tell you there's a little spotlighting effect. Even though the field of view is on the wide side, the coverage fades rapidly near the edge of the field because it's at such a severe angle, so keep that in mind.

Plus, while the P7 has a pretty typical forward voltage (3.3 - 4.2) it has a HUGE drive current (2.8A to get the max output) and there are very few drivers tailored to that sort of current. You could use them on a meanwell ELN60-48 underdriven at 1.3A, which would be more efficient, but lower absolute output so you'd need many more of them.

It's not a terrible LED, and overall performance isn't bad by any means, but it's just not typical for the designs people are using in reef tanks, so you're going to have to do some rethinking. I might suggest looking at the Luxeon Rebel mounted 3-up, which has similar output, but the LEDs are in series so the voltage stacks instead of the current - meaning you can use conventional drivers. Or, the Cree MC-E, which is basically four XR-E emitters on the same die.

All of these super-output LEDs are basically multiple emitters packaged together, so you get higher absolute output but pretty much the same efficiency. You get the same output as 3 or 4 LEDs, but from a single point - so you need to keep that in mind for light spread, heatsinking, etc. too.

If I was going to build a very high intensity rig for a very deep tank, I might use these LEDs in a conventional, tight spacing, but otherwise, I'd have to be convinced they were better than the standard choices.

 

[nieves]

Lots to think about. Thanks, der. Lots of good input.

 

[pookstreet]

Typical sources: ETG, dealextreme, ledsupply. Shop a bit to find the best prices. mpja.com for DC power supplies if you go with buckpucks.

If you get a dimmable driver that can do 0-10v DC analog dimming, you can use the Apex's 0-10V channel(s) to dim based on whatever programming you can dream up. The meanwell drivers come in a 0-10V DC dimmable flavor. The buckpucks come in a 0-5V DC dimmable flavor, so you could probably fake it by only using half the signal width from the Apex.

Thanks! I'll check everything out. I am sure I'll have more questions shortly

 

[der_wille_zur_macht]

I have finished drivers out in the real world that have 4 or 5 months of run time on them based on the NCP3066 chip from OnSemi. This is a constant current switching DC-DC regulator with an enable pin that can be used for PWM dimming, or if you want analog dimming you can have that via modifying the voltage at the sense resistor pin.

It's basically the boost topology example circuit from the datasheet, with components selected (by their formulas and some trial and error) to get the performance I wanted. I have zero documentation at this point though, but I'm in the process of fixing that; hopefully I can post something in the next week or so.

These drivers can run 8 LEDs on a 24v source, with PWM dimming. In theory it's more efficient than buckpucks or meanwells claim to be, but I don't have the tools to actually measure that (just going on OnSemi's claims vs. claims from the other vendors).

The design is all through-hole, so it's "easy" for a beginner to solder, and it can be made on a $.75 protoboard from radio shack. Cost for the entire driver is probably $6 or $7 each. It's around 8 or 10 components.

I'm looking at some other options right now, but this NCP3066 driver is pretty solid. If you don't need the dimming control and/or aren't an efficiency freak like me, there are probably slightly cheaper/easier ways to drive LEDs (LM317 in constant current mode, any of the various linear constant current chips aimed at HP LEDs, or even just big resistors like kcress documented in his recent LED thread.)

For those interested, I started another thread to give some details on the DIY drivers:

http://reefcentral.com/forums/showthread.php?t=1759758

 

[Drake1]

any groups buys going on soon?

 

[stugray]

L98-Z,

"I can't see using these LEDs as moon lights being that great. They're too bright, you'll end up dimming them."

I use two CREE XR-Es for my moonlights and I love them.

Here is from the bottom:

Here is from the tops so you can see the CPU heatsink:

Here's what it looks like:

Stu

 

[dipan]

Can't see the pics, Stu ...

edit ... Hmmmm ... now I can!

 

[der_wille_zur_macht]

any groups buys going on soon?

None on RC that I'm aware of. If you're buying in enough bulk you can usually get good discounts on your own. Deal Extreme will hit like $4.60 or something on cool white XR-E if you buy 10 or more. None of the group buys I've seen from other vendors even hit that price (they're all around $5/pc maxed out).

I use two CREE XR-Es for my moonlights and I love them.

What color are you using? Have you tried them without those acrylic lenses? I wonder if they aid in diffusing the light at all.

 

[Drake1]

ok these threads have gotten way to long and are just confusing for someone reading the the beginning of them. so the XR-E white and blues are still the best but what eln's are the best to use i have seen post from atleast 4 different types. any way to hook them up to an x-10 to get computer dimming or did i miss that in the threads?
thanks jeff

 

[der_wille_zur_macht]

Jeff,

The cool white XR-E Q5 bin is very good. The Luxeon Rebel 100 bin is about the same, but a little wider field of vision. For blues, the blue or royal blue version of either is good.

The Cree XP-G is better than the XR-E but brand new so pricing and availability is tricky. Also, it's not available (yet) in blue or royal blue.

The ELN-60-48 is the driver of choice if you want an AC driver that's dimmable. It will do 12 LEDs. Make SURE you turn the internal current limit pot DOWN to an appropriate value, as these drivers will hit 1.3A turned all the way up. Also, get the P or D version depending on how you want to dim it. P takes a 10v PWM signal, D takes a 0-10V analog signal.

 

[Drake1]

when using leds for frag and plant only tanks is there any reason to use the blues leds?

 

[Altpers0na]

just to color to preference.

 

[der_wille_zur_macht]

For frag tanks, I'd mix cool whites and blues to get whatever whitish-blue color you'd normally want on the tank from MH or T5. For a plant-only tank, (or macro algae refugium or ATS) the jury is still a bit out, but your best bet would likely be warm whites or a mix of reds and blues. For reference, look at the lamps people normally use on these tanks - they're typically very warm compared to what you see on a reef tank.

 

[Drake1]

so assuming i read everything correct on a AGA 125 gallon it opening is 70" x 16" by the high sps theory i would need 112 leds but i assume i could get by with maybe 90 leds?
thanks jeff

 

[der_wille_zur_macht]

Drake, that sounds about right for that tank.