LED Growlight Construction

How complicated would it be to construct 100 watt LED growlights?

I would like to use 5w diodes in 60,90 and 120 degree angles.

20 to a panel

Below would be my desired color ranges

• Deep Blue 450 nm
• Blue 470 nm
• Red 620 nm
• Deep Red 665 nm
• Warm White 430-700 nm

Thank you for any input, I have some electronics knowledge so I am not completely green, just a little sketchy on LED requirements.

First of all, what is a "glowlight"?

Second, the #1 rule for LEDs is they are current devices and thus are best driven by a constant current source/sink. For high power LEDs like the 5W you specified, a switch-mode current regulator is the best choice.

You could use this ready made device:

* http://www.parts-express.com/pe/showdetl.cfm?partnumber=073-052

or you could roll your own using something like this:

* http://www.ti.com/product/LM3404

or use this cool LED Driver selection tool by Linear:

* http://www.linear.com/products/led_driver_ics?gclid=CI7C_I_Y0LECFSVvTAod1GYAqw

I think Steve pretty much nailed it. If you're feeling lazy, I believe there may already be commercial
LED growlights; I know Lighting Science was working on one.

I thank you for your input Steve.

What I am asking about is a growlight for vegetable starts, to get a jump on spring in the northern climes.
Something like the following.
http://www.rhinogrow.com/RhinoGrow_400_Series.php

The difference being that I only want to build 100w modules with 5w diodes instead of 3w diodes.
I anticipate much experimentation to find the right combination of colors.

Thanks for the input Rich. I'm not one to be lazy, more likely I attempt to DYI for the economics value involved. I have a background in fabrication, and I know some about electronics, I'm thinking that this might be a very fruitful experiment.

I appreciate you fellas speaking with me and pointing me in the right direction, and I am open to more suggestions.

I'm no expert on grow lights, but from the little research I've done: Blue light to grow it, Red to get it to flower. Just something to stir the pot (no pun, I assume ;)

So, if you drive them in series (NOT parallel) and probably several series strings, each on it's own Constant Current [CC] driver, you'll probably have a cool setup!

So, you need to determine what power source you're going to use. This power source would supply the one or more CC drivers. I'm assuming this would be plugged into the mains and would best be an SMPS. The higher the supply voltage, the lower the overall drive current (probably more efficient), but higher voltage is increasingly more difficult/expensive. Most of these Switch Mode CC drivers are of the Buck variety, so you will need a voltage that is slightly higher than the CC driver's max output voltage. AND, the more LEDs in each string, the higher _that_ voltage will be.

Now, you could go really cheep and drive the series strings directly from 120VAC (or 240VAC if that's what is on the mains in your area) using one or more high wattage resistors, but that is REALLY inefficient, and will produce a LOT of heat, and can result in blown LEDs (I would run them at, say, 3W, to compensate for the lack of regulation). I would, also, but spike suppressors across the power line, and include an EMI filter (as LEDs are sensitive to spikes and such). ALSO, IF YOU DO IT THIS WAY, MAKE SURE THERE ARE *NO* EXPOSED WIRES ANYWHERE, AS THIS WILL BE *HOT* AND *DANGEROUS* AND *POTENTIALLY LETHAL*!!! ALSO BE VERY CAREFUL HANDLING IT DURING THE CONSTRUCTION, TESTING PHASE. *USE ALL PRECAUTIONS*!!!

If using resistors, follow this rule of thumb: the higher the resistance, the greater the "regulation". An infinite resistance = constant current. But an infinite resistance would need an infinitely high voltage, so that, obviously, isn't practical, so you have to find that happy medium between "regulation", heat production, and number of LEDs per series string. You might find that the cost of the high wattage resistors would make this approach impractical (unless you can find a super deal at one of the surplus electronic stores like All Electronics).

So, your job is to workout the arrangement based on your budget/requirements/preferences/logistics/etc.

I meant to say "directly from 120VAC through an AC-to-DC converter (e.g. rectifiers and filter cap)".

The information you supply is outstanding, I'm already starting to get the picture much more clearly, of course I am sure that I will have to do more research but you have definitely given me a great jump off point, thanks again for your time and advice.

I may return with additional questions as my research continues, and you fellas should know that I really appreciate your help.

~regards, DJ~

Cool, I'm glad I was of help.

One suggestion: when you do ask your followup questions, I suggest starting a new thread with each question. That way, it will get "more eyes" on it. If you ask the question here, only those who have responded to this thread will see it.

Also, your question(s) might apply to other cases (beyond Growlights) and thus, be helpful to a wider scope of people searching for answers on this forum (especially if the title of the thread is nice and descriptive In other words, your question will be under a title that describes that question, and not be under the title "LED Growlight Construction", which may have little to do with the question.

Another thing to consider: The most efficient way to run a high power LED is via PWM, BUT, consider that flashing light might be detrimental to the plants being illuminated. I don't know if that is an issue, but thought it worth considering.

That's something I never thought about. It may be viable, as long as they all didn't flash at the same time, perhaps a flip-flop could somehow be incorporated, or even supplemental steady side lighting in the form of CFL's. Food for thought, thanks.

http://www.waitingforfriday.com/index.php/Controlling_LED_brightness_using_PWM

http://www.youtube.com/watch?v=jFI7Ahf0lZ8&feature=player_embedded

Perhaps, if a microcontroller is used, it could control all of the PWM in an array of LED strings (i.e. one PWM output per string), and each PWM output could be phase-shifted such that there is always only one string on.

But, then, the direction of the light would rapidly shift. Would the plant have the equivalent of a nervous breakdown trying to deal with a "sun" that keeps rapidly shifting position in the "sky"?

Also, would there be an optimal frequency, or at least a benign frequency?