DIY 150-900W fully modular LED lighting driver

[varikonniemi]

This is a LED lighting driver that i made purely out of parts rescued from going to the trash. Only the LED emitters are bought.

I needed more light for my chili plants, and decided that LED lighting is the future and the way to go. Unfortunately all commercial LED lights are very expensive, so i looked around and found out i actually have all the parts necessary to build a heavy-duty LED driver myself.

The LED emitters themselves are not that expensive, and since they will virtually last forever they might be the cheapest method for lighting at the moment (if you can build the driver yourself, that is).

So yesterday i finally finished my lighting project, and a big smile creeped on my face when the light went on, and everything worked out as planned

Currently i am running one 150W LED module, but in the next few days i should get an additional 300W module up and running

In-depth details and pictures of the driver, LED module and the build process can be found at my blog http://varikonniemi.wordpress.com/2013/ ... led-light/

Questions, comments and critique welcomed, as always :)

[hrmph]

Any reason you went for white leds instead of the red/blue mix that most led grow lamps use? Looks cool, your electrical know-how is impressive.

[Licho]

Reason can be to make chili happy with least power spent!

The best match to chlorophyll absorption is the winner:

[hrmph]

Reason can be to make chili happy with least power spent!

The best match to chlorophyll absorption is the winner:

Lights that put out other parts of the spectrum than those peaks used primarily in photosynthesis are wasting energy. That is why almost every LED grow light on the market focuses on red/blue/purple.

[klapmongool]

Don't the plants need heat as well? Or do the LEDS give off enough heat?

[Sabutai]

Chili plants...? Yeaaaaaaaaah right

[varikonniemi]

hrmph, Licho.

This is a topic of hot debate, have a look at this picture i compiled:



The second peak in the spectral output comes from secondary fluorescent materials added to make the desired color temperature. The first peak is the primary LED emitting spectra. Warm white LEDs have more of these secondary fluorescent materials, so their second peak is proportionally higher and goes further towards red.

There are other ways the plants utilize light, then the primary two chlorophylls. There is even study going on about a third chlorophyl...

One main secondary pigment is beta-carotene, and there are yet others. So blindly looking at the chlorophyl absorption spectra will not be beneficial. For the plants to "feel" a natural environment, all their photochemical pathways should be saturated, just like the sun does.

I admit, in my setup there is a need for deep red light in the range of 660nm especially for the flowering/fruit production stage, and this is something i am looking into in further upgrades.

But as a general plant light, the white LED (especially mixed cool white:warm white 2:1 for a broader spectral coverage) should have a good match with plants off all kind.

[1v0ry_k1ng]

Chili plants...? Yeaaaaaaaaah right

[varikonniemi]

Don't the plants need heat as well? Or do the LEDS give off enough heat?

The plants need heat in the form of a suitable ambient temperature. Excess heat produced by the lighting only contributes to the plant sucking in more water so that it can evaporate it from the leaves, to cool them down.

This wastes energy, and can lead to excess buildup of certain nutrients if they get drained in with the water.

[hrmph]

varikonniemi, where is that graph you posted from? Also, I'm curious what growing method you have in mind for your peppers.

[Cheesecan]

Actually all wrong and right simultaneously.

Different plants have different absoption spectrums. Additionally their light needs will differ depending on growth stage. Plants produce pigments inside their tissue and different pigments depending on state in their life cycle. Each pigment in turn acrivates different enzymes e.g fruiting, grow stalk, leaf etc.

To conplicate things further pigments have different absorption thus most plants appear green because what they absorb the least, and converaely reflect the most is green light. So it might appear wise to use only reds and blues. However that would mean that most light would be absorbed at the top of the canopy. The lower leaves thus receiving low light, going bare from light starvation.

So in other words. Plants have fully adapted to the sun and what you see in plant absorp. spectras is an illusion. You want to have a spectrum that activates all the pigments and manages light flow over time.

That's the basic biology behind it that you need to know. For details read journals and studies on subjects such as phytochrome, plant pigments and regulation of co2.

When it comes to engineering an optimal light source. It is more complex than you might realize. The simplest is to emulate the sun, which trad. Gas discharfe lamps do.

Complexity arises with narrow band sources like led which need to be combined to achieve same or greater effect as a full spectrum.

The rough outlines is you have a model which you optimize for external factors eg. Cost. Efficiency. Size. Etc. To reach the optimal solution.

I developed such a model a few years back which I am plannibg to patent. Ive done extensive research and come up with a matgematical model by which geowth potential can be measured objectively for any light sourve. I believe there are a few others out there too however manufacturers have yet to empkoy these methods. Innovation largely ceased in the 70s because there were no light sources able to produce composite spectrums at high efficiency.

Edit: Sorry for the spelling I wrote that on my phone. If you're interested in this topic or looking for inspiration or even just kicks I could recommend the website http://greenpinelane.com/

[varikonniemi]

That's basically what i said.

Where i disagree on is that HPS and MH lamps both have very narrow spectral bands, whereas the LED has an almost full spectral band when mixed cool white with warm white.

Even commercial growers are switching to LED lighting, because it is so much more energy efficient, and cheap because the LEDs last a long long time.

hrmph:

I cannot remember where i got that picture from, but i have overlapped a picture from a LED datasheet with a plant absorption efficiency picture from some pretty convincingly looking plant biology site.

here is a quote from them i saved, google it and you might find the site

Photosynthesis depends upon the absorption of light by pigments in the leaves of plants. The most important of these is chlorophyll-a, but there are several accessory pigments that also contribute.
The measured rate of photosynthesis as a function of absorbed wavelength correlates well with the absorption frequencies of chlorophyll a, but makes it evident that there are some other contributors to the absorption.

The plot of the absorption spectra of the chlorophylls plus beta carotene correlates well with the observed photosynthetic output. The measure of photochemical efficiency is made by meauring the amount of oxygen produced by leaves following exposure to various wavelengths.

I am planning to grow them in normal flower pots & soil. Hydroponics systems i would not consider since they use chemical nutrients, and organic hydroponics systems are still over my head, but the theory behind them looks interesting... Maybe some day -_-

[Cheesecan]

Narrow as in the ones not full spectrum.

When you're using white LEDs, you should try to find ones with the highest luminious efficacy and drive them at the current with best tradeoff between cost and efficacy.
http://www.leds.de/en/High-Power-LEDs/C ... 720lm.html

As I can tell you may be around ~85lm/W or so considering you're underdriving one of your LEDs. You still want to get that higher, especially if you plan on getting more. The electricity savings will outweigh having to buy more LEDs.

[varikonniemi]

The first 150W module i did is not perfect at all, and should only be considered a prototype, as i have explained. The LEDs are around 85 lm/W, but the series resistor i had to use wastes a considerable amount of energy.

The 3x100W module i am currently building uses identically specc'ed LEDs with 95 lm/W and a combined forward voltage of 90-105V. The output after the regulator is 110V so the current regulator must only waste 5V@3A=15W so no series resistor is even needed.

The one you linked is 103 lm/W, that is great. But also it is INSANELY more expensive. I paid 0.0038$/Lumen, that one costs 0.0332$/Lumen which makes it 10x more expensive.

Also, all "wasted" energy is only wasted during those months we do not need to heat up the house in the summer, 3 months at most. So 9 months a year all "wasted" energy is not wasted at all.

[Cheesecan]

That cheap? I'd be careful about using emitters from taiwanese and chinese companies. Been down that road and found wrong numbers in datasheets. Wouldn't be surprised at random failures either.

[varikonniemi]

Testing out the finished 3x100W panel @ 3A, with normal working room fluorescent &some spot lighting turned on. It really just puts out so much light that it seems to be the only light source.

All i can say is that they promise a minimum lifetime of 50000 hours for these emitters and that the seller has 99,8% positive feedback on eBay. They come with a 3 year warranty.

They are specified to run at 3-3.5A, and i will be running them at 3A, so that should also help keeping them in good shape for a substantially longer time. (27000 Lumens is at 3A, at 3.5A they should put out 28500 Lumens.)

The more credible manufacturers like CREE promise 100000 hours, so there definitely is a difference. Too bad even comparable CREE emitters cost 3x as much.

[KaiserJ]

damn you for living far away, i would pay you in chilis to build me one of these.

it all looks very nicely constructed, and it feels great to save money by creating something yourself. keep up the good work! i suggest using a cheap mylar safety blanket (like the kind from road safety kits) to line the box with to maximize reflection (also some primer on the plywood and some caulk along the seam edges to protect from damage from accidental spills and moisture wouldn't hurt but it's not a pressing issue)

[varikonniemi]

Thank you for your kind words :)

I am planning to line the walls with black-white construction plastic. It it really cheap, and the white side reflects 85-90% light, whereas mylar reflects 90-95% and is much more expensive.

The room is a cold cellar storage compartment with no floor or heating, so any spills would only mean some wet sand under the wooden elements used to walk on (i really don't know what these are called).

(PS. Today i won an auction of 50pcs of 1W 90 Lumen 660nm LED emitters. These were the only thing i needed for a satisfying complete spectral coverage. I don't have any clue how to mount these yet, and it will take a week for them to arrive in the mail. But if and when i get this expansion module working, i will be more than satisfied with this project.)

[Prominence]

Big waste of time and money when there is a sunlight outside. Better to just get greenhouse like rest of the farmers and feed carbon dioxide for more growth.

For room illumination, it's best to use LED bulb that emits slight yellowish light with color temperature around 2700K to 3000K for safe viewing.

[Cheesecan]

If you live in a country where one third to half of the year of the year is winter, growing in a greenhouse is too restrictive. Slugs and insects will come and ruin everything too.