DIY LEDs - The write-up

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This is a little bit off-course, but has anyone made a (terrestrial) plant light with the Cree LEDs?

I'm almost finished building mine - it's got 20 royal XP-Es, 4 warm white XP-Gs, 10 degree lenses, 2x MW LPC-700s, aluminum 1x2 square tubing. Like my other fixtures, it's designed to be up on the ceiling, out of sight out of mind. I can post pics if anyone's interested.

Anyone do anything similar? I'd really enjoy seeing...
 
Yea I made a fixture for growing some habanero pepper plants.... it was working great and growing nice plants until friggen spider mites got in on the party :)

Nothin fancy, using mostly leftover LEDs from my aquarium build (and all the other bits as well), just had to buy some warm/red ones.

leds.jpg


Finally killed the spidermites and plants growin again.

One thing I noticed and found weird, is that the parts of my plants under the direct light grow the slowest... once the plant branches outside of the intensity zone the branches get way longer. I don't think plants need anywhere near the same intensity as corals to thrive but I have way too many other issues going on to say that definitively yet.
 
Quartapound said:
Thanks for the tip,
I will check this and report back,
Am I correct that the forward voltage drop of xpe RB is ~ 3.5@1000mA. ... so 14 should consume ~49v
Click to expand...

You'd do better to measure it with a voltmeter. It can vary quite a bit from LED to LED.

CJ
 
Love the recycling!

Questions:
1) What lenses?
2) How far away were the plants?
3) What drive current?
4) What photoperiod?
5) Those reds - 630 or 660 nm?

I have read a lot about people experimenting with the LEDs, and am under the impression that there are a couple ''bottlenecks'' that I'm going to have to watch out for -

1) photoinhibition - once the plants get a certain amount of light in a time frame, it's not just pointless to supply more, but it is also detrimental. This might be why you ran into the growth you describe.

2) serendipitous wavelengths - it seems that when people build their fixtures with ONLY blue and red LEDs, a lot of them run into poor/weird growth at some point. When they add full spectrum light ie HPS/MH/fluoro, the growth returns to normal/great. This makes it appear that certain plants may require certain other wavelengths, maybe not for energy, but to ''flip switches'' or regulate growth somehow.

So why is my fixture 20x royal blue & 4x warm white? The royal blues are ridiculously efficient at turning electricity into photons - 1/2 of the electricity that goes into them comes out as photons, centered at one of the active peaks of chlorophyll. Plus they are dirt cheap on a group buy @ <$3 each, as compared to the red 660s that are at least twice as $$ and less efficient... I added the warm whites partly for aesthetics and partly to hopefully fill in some of these serendipitous wavelengths, although the fixture will be suspended over plants that are sitting near a window...
 
TheFishMan65 said:
What is the output voltage of the ELN when 14 LEDs are connected. I would think you could reach 700ma with 14 LEDs. But measuring the voltage should answer that.
Click to expand...

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

reefermad619 said:
Cree recommends a max current of 700ma for the rb. At least for longevity purposes.
Click to expand...

I was referencing Cree's XP-E white paper, where it states the typical forward voltage drop of a RB XP-E @1000mA is 3.5 volts (for reference purposes)


CJO said:
You'd do better to measure it with a voltmeter. It can vary quite a bit from LED to LED.

CJ
Click to expand...

I could do this but not sure how it would help in my "resolution". I don't have any more extra LED's to swap out for ones with a lower voltage drop.



Still not sure if things are good the way they are, or if I should rewire things to give me 2x9 LED's in parallel with each circuit protected by a 1amp fuse.

The second driver/string was going to power 10 CW XP-G's and the remaining 4 RB. (to maintain a colour ratio of 2:1 RB to CW)

if I wired all the RB on one Driver (2x9 parallel) this would also allow me to control the colours completely independently... (i've also heard its not a good idea to mix LED's on a single driver, however the 14 I'm trying to power up at the moment are all RB).


confused as to which step I should take next!! (wish it would just say 700mA!!)


...just updating, I can achieve 700mA with 13 LED's also... it's only when I add that last one that current draw won't exceed 450mA or so...
 
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Quartapound; Sounds like your ELN is maxing out it's voltage a little low.

Use a jumper to short out one LED and see what happens to the current. If it goes up markedly then topped-out-voltage is the problem. The solution is to try a different ELN, or run one less LED, in the string (14 is always a cr@p-shoot), or swap out a few of the LEDs having the highest Vf.
 
Quartapound said:
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
Click to expand...

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.
 
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!!!
 
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.
Click to expand...

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