DIY LEDs - The write-up

[der_wille_zur_macht]

the output voltage is 46.81V when connecting 14 in series, adjusting the SVR2 pot I can only reach amp draw as high as 422mA. (it reaches this number about halfway through the travel of the SVR2 potentiometer, turning it the rest of the way doesn't increase current any further) (dimmer pot set to 10V)

the output voltage is 42.04V when connecting 12 in series, with SVR2 set to 700mA (easily acheivable) and dimmer pot set to 10V

I haven't read your whole discussion so maybe I missed this, but have you ever touched SVR1? It's a voltage limit pot. Setting it low will cause the operation you are describing (it stops the driver from raising voltage high enough to hit the desired current). If you've never touched it, maybe it came from the factory too low. If I were you, I'd do this:

1) Configure the driver with 12 in series. Set SVR2 to give 700mA current
2) Configure the driver with 14 in series. Turn SVR1 up, while watching current. Stop when it gets to 700mA (maybe a fraction of a turn higher to allow wiggle room for environmental changes).

You made a point of mixing LEDs on a single driver - this is a complete non-issue with a single series string, as long as the current through the string is below the max for the lowest-rated LED. With parallel strings, you just have to ensure the makeup of each string is the same, i.e. you don't want 10 whites on one string and 10 blues on the other - you'd want 5 of each on each string.

 

[der_wille_zur_macht]

kcress beat me to the punch but forgot about SVR1.

 

[Quartapound]

kcress beat me to the punch but forgot about SVR1.

thank you kcress and der_wille_zur_macht, I will try that right now and report back

 

[Quartapound]

THANK YOU!!! kcress and der_wille_zur_macht,

that's EXACTLY what it was.

SVR1 was set too low (from the factory).

following der_wille_zur_macht's instructions I was able to raise SVR1 to the point that I achieved 700mA with all 14 LED's in series.

when checking with a voltmeter after the SVR1 was set, it is now 48.12V.

Sooo now I've got 14 led's in series running @700mA, and a proper voltage output.


THANKS AGAIN!!!

 

[der_wille_zur_macht]

This is the tipoff:

the output voltage is 46.81V when connecting 14 in series, adjusting the SVR2 pot I can only reach amp draw as high as 422mA.

With SVR1 "centered" it should hit 48v. With SVR1 turned all the way up, iirc, it's like 52v or something.

 

[TheFishMan65]

42.04 volts for 12 LEDs is (whoa who would have thunk) 3.503 volts per LED. So if you add to more you would need 49.046 volts. Since it is maxing out at 46.81 you aren't getting enough voltage push the current through. I expect when you change SVR1 you will be right near the expect 49 volts.

 

[reefermad619]

The max current was retroactively changed to 1000 mA in a datasheet revision some time last year. It's totally safe to run these at 1A and you'll still get projected lifespans and performance from them.

Thanks dwzm. The info I read was from a certain group buy site. Here's their link... http://www.cree.com/products/pdf/XLampXP-E.pdf

Can you post the updated link? Thanks.

 

[ReeferVinnEE]

Tagging along, great thread!

 

[Robert Patterso]

Ok I'm in and no I have not read this whole thread. I will if you all insist. What I would really like to do is start off building something simple. I would like to build an led set-up for my ATS. Most all the led's would be red, yes red, to grow algae. From what I have read 1w led lights would be best for this application. The problem for me is I know absolutely nothing about led lighting. Soooo if someone would be so kind as to tell me what I need, where to buy it that would be greatly appreciated. I will be lighting an area about
10"x14". I will go back and read everything I need to as far as how to assemble it. I should have all the tools I need, I'm a machinist/welder and have access to all tools I would need.
Thanks in advance

 

[kcress]

Nice one DWZM. I just assumed since he was diddling pots that one was also tried.

Robert Patterso; Go to TheFishMan's home page for a LED build summary.

 

[TheFishMan65]

reefermad,

That might be the latest sheet it shows the RB going to 1000ma. Only the Ambers and Reds are limited. Green, blue and white goto 1000ma.

 

[miwoodar]

Woo-hoo! I'm sitting on a pile of LED parts. However, I ordered 20 awg wire but received 22. Can I still use it? (HLG 185-42 running 66 RB/B @ 700 ma max and HLG 120-42 running 24 NW @ 1.45 amp max.)

 

[Garage1217]

Woo-hoo! I'm sitting on a pile of LED parts. However, I ordered 20 awg wire but received 22. Can I still use it? (HLG 185-42 running 66 RB/B @ 700 ma max and HLG 120-42 running 24 NW @ 1.45 amp max.)

No problem with 22awg, it is rated at 7amps on the conservative side.

This is a good reference for some of you wondering about wire size / current capacity. Use the "maximum amps for chassis wiring table" for your reference. While conservative on the chart, I will generally spec wire rated at double the current capacity for the said project. For example, with 1.5A maximum, I would use a minimum of 24awg.

http://www.powerstream.com/Wire_Size.htm

 

[wfournier]

Woo-hoo! I'm sitting on a pile of LED parts. However, I ordered 20 awg wire but received 22. Can I still use it? (HLG 185-42 running 66 RB/B @ 700 ma max and HLG 120-42 running 24 NW @ 1.45 amp max.)

You're better off with 22 for internal wiring, you might want something heavier for the run to the driver depending on the distance.

 

[miwoodar]

Thanks guys - much appreciated. I'm stoked to get this thing done!

 

[reefermad619]

reefermad,

That might be the latest sheet it shows the RB going to 1000ma. Only the Ambers and Reds are limited. Green, blue and white goto 1000ma.

I saw that. I know the MAX current is 1amp, but further down it says cree recommends a max of 700ma for longevity purposes. I plan on runnin my rb at 700ma. I just wanted to make sure I read the data sheet right. I'm a chemist by trade, not an engineer. Thanks for the help. Oh, that cutter site is hard to navigate. I think I'll stick with rapid

 

[Quartapound]

You made a point of mixing LEDs on a single driver - this is a complete non-issue with a single series string, as long as the current through the string is below the max for the lowest-rated LED. With parallel strings, you just have to ensure the makeup of each string is the same, i.e. you don't want 10 whites on one string and 10 blues on the other - you'd want 5 of each on each string.

Everything is still working GREAT with the LED's (I'm new to saltwater in general and had only been using a single t5 to 'get me by' before I got my LED's working)... I have so many colors in my tank now that I never knew existed!


I am currently running
14 RB XP-E @ 710mA on one driver

and

10 CW XP-G & 4 RB XP-E's @ 710mA on the other driver.

Am I short-changing myself by running my Cool Whites only at 710mA?

Since it's considered "safe" for the RB's to run at 1000mA, would I be better off adjusting that driver to ~ 900mA? ... would there be a noticable difference?

Does anyone else run the CW and RB on the same driver, and if so what are most people setting the current draw to?

 

[TheFishMan65]

reefermad,

What page has the note? I can't seem to find it. Cutter takes some getting used, but for quantity they are usually the cheapest. Try products->CREE LEDs->premounted on board->20 mm MCPS->star. Then there are only three pages to look through .

 

[TheFishMan65]

Quartapound,

Do you need more light? I bleached my corals with too much light. If so than you may be short changing yourself (but only if you can keep them cool).

Yes, I have read of other mixing them.

Set the current for however much light you need.

 

[der_wille_zur_macht]

The note is way down on one of the last pages, and is with respect to meeting a certain Energystar lifetime certification spec. I don't really consider it to be something that applies for us. Especially considering most of us are WAY over-cooling our LEDs compared to the targets described in Cree's thermal management documentation.

Quarta, I agree with fishman. Turn the driver up if you need more light - we can't really answer the question for you. You're not "short changing" yourself if you already have the light you need! It can be deceptively easy to burn or bleach corals with LEDs, so make any upwards adjustment gradually if you already have livestock in the tank.