Questions for Oldmac -

Hi Oldmac â??
Iâ??ve been lurking around here for a while, and decided I needed to join up and see if I can tap into some of your experience. Iâ??ve seen that you use a hybrid fluorescent/led fixture and was wondering if there were any pitfalls that you would pass along so that I can jump over them! I have been using a homemade fixture that utilizes (6) 55 watt PL-L lamps, changing out the lamp spectrum based on the plant maturity. The fixture uses reflectors that are 4â?� x 22â?�, and what I have in mind is to build up a new unit that will use (4) of these assemblies alternating with (3) new modules that are the same dimensions, but that utilize (32) 660nm leds on each module (probably the new Osram Golden Dragon +â??s). I have been pretty impressed with the PL-Lâ??s, but they are lacking in deep red and this seems like a good way to get where I want. I grow in a scrog format, so deep penetration is not an issue. Initially, it seemed like a good idea to mix lamps that were somewhere around the 4100k-6500k with the leds, but after reviewing a bunch of spd charts, it looks like there is plenty of blue in all of the available spectrums. Iâ??m thinking that using 2700k-3000k lamps would make more of the orange-low red wavelength available to round things out, and still provide enough blue. Iâ??d appreciate hearing any input that you have regarding this or any other aspect. Thanks.

Hello OldSparky,
Welcome to the boards and I'm flattered by you're asking for my input. :)

I have built two different hybred lights, one I have used for 3 years or so now and the other was just a few months then gave it up and I have to admit it was a failure.
First the failure; it consisted of 2- TI problooms mounted in a frame with 4- 4' T5s 3000k driven to VHO levels (85w/bulb), 2 bulbs to each side of the TIs. It just did not achieve good light mix, but did square off the lights footprint to cover a 4'x4' area. Problem was the center was recieving just LED light, a few rows on either side got a mix and the outer rows only got T5 light. It still beat a 1k HPS but was using 1000w total and I found I could get the same results the the 2- TIs (660w total) and a light rail.

My other hybred did not start out to be one. It was going to be red and white LEDs but I got burned by a chinese mfg of the whites and had to shit can them. I used T5s instead (full spectrums then now 2700k) because I had so much invested and the design was physically good.

This light is in my personal grow, where I use a GI Grow rotating garden (144 plants) that's been heavily modified. At the center is a 6"dia boroscilicate glass tube that needs to produce light in a 360 degree pattern. I used a 24" piece of architechural aluminum in a octogonal shape, mounted inside the glass tube. Each side has 1- 2' T5 2700k driven to VHO levels (40w/ea) and a row of 30- red 635nm Crees that are 2w nominal tho I drive them at 650ma and they produce abt 1.75w each. So there is 320w of T5 and 420w 635 red for a total light of 740 watt. It outperforms the 1K HPS it replaced.

At the time I built it the best red LEDs seemed to be the Cree's. I only wish some good 660nm LEDs were available at that time, I think it would work even better. BTW I like those PPL lights, looked at some 105w PPLs awhile ago but when I went to buy a fixture they had discontiuned it. You are absolutely correct about the amount of blue in a flouro, even a 2700k. I originally used 2' T5s that were "full spectrum" cause I was gun shy from my white diode experience but when it came time to change bulbs I figured out what you have, there is a large blue bulge in the SPD of all fluros.

IMHO if you could combine one or two 55wPPLs with a row of those Osram 660nm LEDs in the same fixture you would achieve a better blending of light wavelenghts. I think that if they are in seperate fixtures you may find what I did with the 4' hybred light, uneven blending. It is my belief that the octogon hybred works so much better because of the closeness of the LEDs and T5s. It is possible that the fact the plants are moving also helps the plants to see all the light better (kinda like a light rail).

Thanks again for asking for my input and I'm more then willing to kick ideas around with you. I should note that I also use some other supplemental lights with this. Good luck and good designing and growing to ya. :thumbsup:

Good morning, oldmac.

I appreciate your speedy response and your input. I think that I didnâ??t do a good job explaining my proposed physical layout for my new fixture. I plan on using only one fixture (well, perhaps with some supplemental sidelighting), and it would alternate PL-L/reflector assemblies with led heatsink modules, both of which would be 4â?� wide. An end view of new fixture would look like this: [PLL][LED][PLL][LED][PLL][LED][PLL]. The dimension across this view would be 28â?�, with the overall footprint being 22â?�x28â?�. It seems to me that this gives the best potential blending of the spectrums â?? if Iâ??m missing something here, please let me know.

I am mildly concerned about the ratio of the luminous flux generated by each type of light (or more accurately, the par ratio). This layout would have 220 watts of PL-L and about 100 watts of ledâ??s. The new Golden Dragons are supposed to be far more efficient than past models, but I am having a hell of a time trying to come up with a meaningful comparison of components. Depending on the manufacturer, they are rated in mw, lm, mc, etc., and to convert from one unit of measure to another seems to require sacrificing a goat in the light of a full moon. Starting with the 2-1 ratio of light sources is driven more by trying to achieve good blending of the light sources vs. optimizing the spectrum. I have had reasonable success with using straight PL-L, so adding this amount of deep red seems fairly conservative. You are loaded in the other direction with an approximate wattage ratio of 3-4, but it seems to me that using wattage as a comparison might be misleading because of the changing efficiencies of converting watts to light. If you can shed any light (pun intended!) on this, I would certainly appreciate it.

I had never seen the GI Grow system before. Very interesting â?? Iâ??ve spent a good portion of the morning looking up links! Thanks for your help.

Hey again OldSparky,

That was a much better description of the light layout. I now have a much better picture of the light. From a light distribution stand point you need to figure how high above the plants you can run the PP-L lights then do a little ruff math to figure what type of lens angle you need or if you need a lens at all. Your lights have a 8" center to center, so to keep it simple lets say you keep the lights 8" above the plant top. That would mean you need 45 degree minimum and 60 degree would be even better in this case. If the LED has a light spread of 120 degree or more it will loose serious luminous power to the plants.

Your right about the confusing deal between various light sources. It all comes down to total Photosynethetic photons per unit of time, expressed as umols/s (micro moles per second). This is what the scientists use when studying a plant, problem is few mfg's of lights use this. (Theroreme Innovation does) The only person I've seen able to convert the various light sources to this is knna, who was just around before. Not sure the math myself but someone does. Heck, I wouldn't know a micro mole if it bite me in my ankle.

But we can compare most LEDs to each other. Most mfg provide Luminous power in mw (micro watts) so as long as the lens angles are the same you can make a direct comparison. Speaking of that you should check out the 660nm reds from LedEngin, inc and then the prices at Mosuer. You'll find the Osram Dragon plus is a 1w diode and sells for $6.80 or so as a SMD. A 5w Engin is about $12.15 mounted on a MCPCB star. So the Osram may be more efficent watt per watt but is not as efficent $ to $. LedEngin even makes some 15w diodes (tho 660 is no longer available) Weezard used a few of those for a small light setup, their luminous power is measured in WATTS.

As to what ratio is best mixing various light sources, I'll tell you what I told Weezard a long time ago; "As much as I love science and believe in the Law of Physics, when it comes to LEDs there is something of a black art to it." Dat's why we need Weezards, 'ya.

So, there's some more to think abt. I do like your light design, gots lots of potential.:thumbsup:

"I'll tell you what I told Weezard a long time ago; "As much as I love science and believe in the Law of Physics, when it comes to LEDs there is something of a black art to it." Dat's why we need Weezards, 'ya."

:o

Great to have ya back, O. M.

That's some great advice BTW.:giveflower:

Aloha nui,
Wee Zard

Thanks for the continuing input, oldmac.