Quote Originally Posted by Crunchypants
My friend, I've read your stuff here and at Steve F.'s site. I want to build a dedicated flowering lamp using Ledengin 15 watters. (4 reds, 1 blue, and possibly 1 warm white; LM 317's so I can tweak the ratios.) Essentially, a copy of your 4+1 cake pan lamp but built on a 4 x 18" finned heatsink so I can see what's going on under it.)

If I were to post my picks for power supply, resistor ratings / values, etc., would you critique and perhaps offer some guidance? I have already purchased the Mastech 3010 you've talked about.

Hoping you'll see this,
Crunchypants
Aloha, CP
Saw your post in KNNA's thread.
Answered it, sort of.
This is prolly a way mo' betta place for it though.
No wanna hi-jack da "bean counters" thread,ya

Happy to help, brah.
Dunno 'bout critique n guidance.
But, I'll kibbitz gleefully.

Let 'er rip.
Weezard

Oh, went and got the post from KNNA's thread.
Here, 'tis
"
The Herding instinct in Photons and micro-einsteins.
Quote:
Originally Posted by Crunchypants
Weezard, I'm planning to homebrew a version of your 4+1 x 15w. light. :thumbsup:Looks like the Ledengin LED's have a 90-110 degree beam, though. Would you recommend additional optics or did the 15's work okay for you unmodified?

Mine are mounted in a deep aluminum cake pan which serves as a reflector.
Didn't find lenses for the ledengins but the 5Watt leds that I lensed are clearly better than the same configuration without the lenses.
Would call it proof if the red leds were identical.
The lensed set is 660nm., the un-lensed are 625nm.
Perhaps the difference in efficiency compensates.
Ah dunno.
I just ordered more lenses.
Will install them on the 625nm lamp and start taking pictures
of the progress.
If you find, say, 40 degree lenses that fit the 15W ledengin lens, please drop me a line.

Also, MPJA has a 28v. / 5.5A power supply (the 24v. is out of stock for awhile). I was thinking getting one to power 2 parallel legs of (2) 15w. 660's, with an LM317 on each leg. Am I just making extra work for myself by not running a 24v. supply into a single LM317 and parallelling (4) 660's off the 317? Seemed like a bit of current to push through a single 317, but I don't really know.

LM317 has a absolute maximum of 1.5A!
You might want to use an LM138 - 338 instead.

Driving an approximately. 12V led from a 28V supply will work well if you run the 2 parallel sets in series.
That will give you 4V headroom but would have to pass 2.1A.
That would require a pass transistor, etc.

So the LM138 series with a max of 5A. would probably serve better for ease of design.
Google the LM138 series for a quick and easy schematic.

The problem then is the blue led which uses closer to 15V, for peak efficiency.
I use 2 separate supplies because dissapating "excess" energy just rubs me the wrong way
My next ledengin lamp will have 2 Blues.
The goal here is to waste as little power as possible in the regulator.

I would like to underdrive the LED's slightly, and have some extra headroom in the build. Thanks!

Good idea!
I limit mine and use a thermal switch in series with the fan to keep everything under 50C.
Better Photons:Watts = less waste heat to deal with as well.

Easy lamp to build and it will work for flowering.
Mine covers app. 2 sq ft. and takes 2 or 3 weeks longer, start to finish, than HPS.
But the quality?
Wicked good!:stoned:

Let me know if I can help.

Aloha,
Weezard "