DIY LED plant lights
 

I have been using fluorescent lights to start my seedlings indoors and started to look for the LED plant lights, but the good ones are still quite expensive. I found 1W blue and red LEDs in the local electronics store and got my DH excited about a new project. First prototype with three blue and three red LEDs is now ready and set-up for testing. If this works we have materials to make three more of these modules to build the whole light fixture.

Sari

I like how they are mounted on a heat sink. I have a question that you you may have to ask your DH, how are you limiting the current a resistor or some kind of driver?

The heat sink may be a bit overrated, but we had such thing laying around. My DH machined three grooves on the heat sink where we glued strips of circuit board, for soldering the LEDs. I made very simple layout for the copper strips on the computer and printed on transparency film, which was transferred to the circuit board treated with UV sensitive coating with the UV light. We went maybe a bit overboard when building the prototype, but since these LEDs are just mounted by soldering the legs, we got them on the heat sink by using the circuit boards strips embedded in the grooves.

I do not have to ask my DH about the current limiting, since I calculated the resistor value. The LEDs are rated for max 400 mA, but we are limiting them now to 300 mA, with a 64 Ω power resistor. The power supply is an old 19.5 VDC laptop power supply which is rated at 4.7 A.

My DH planned to build a driver, but this is now a prototype for testing, so we needed quickly make something to power it up. My DH is experienced with power electronics, so he'll do the more demanding stuff. We have the same degree, but I have been doing mainly software and product engineering, so with electronics I'm only good when it is about applying the Ohm's law. :D

Sari

I understood just about every bit of that.:lol:
Would a simple dimmer switch/rheostat work instead of the resister as long as it had the right range I would think it would?

Sari I found 120 VAC LED lights at the store that you can change the color on, will they work?

You have me thinking now.;)

Worth

Rheostat or variable resistors could be used to vary the current, to change the light intensity, but it should be constructed so that the resistance can not go too low, which would cause the current rise above the LED's maximum rating.

Many of the decorative LED systems have quite low light intensity and the wavelength of the light may not be optimal for plant growth. I have seen that some guys have built grow lights from the ready made LED strips, so it could work also, even the individual LEDs are lower power.

I have used just 470 nm blue and 625 nm red LEDs. The guys who go really hi-tech and are trying to optimize their lights use multiple wavelength blue and red LEDs in same light fixture. I was looking multicolored RGB LEDs, which have blue and red at different wavelengths, but those are much more expensive than the single color ones. I have done a lot of reading now and based on the information which I have got, I may add pure white LEDs to my light, since some people have good experience with them. The plants use mainly blue and red wavelengths, but some other colors may also be beneficial and the pure white LEDs should have plant friendly spectrum. Many of the LED plant lights are made for people who need to keep their plants in closets whole time, so I have a bit different needs, when I am using these just for seedling growth and not for bud production ;).

Sari

[QUOTE=Worth1;390742]I understood just about every bit of that.:lol:
Would a simple dimmer switch/rheostat work instead of the resister as long as it had the right range I would think it would?

Sari I found 120 VAC LED lights at the store that you can change the color on, will they work?

You have me thinking now.;)

Worth[/QUOTE]


I'd say a typical dimmer switch that goes in a house generally won't work. They work by clipping part of the AC wave form essentially acting like a pulse width modulated power supply. With part off the AC cycle missing the RMS (for people that don't know what RMS is it's a type of weighted average) voltage drops. When the dimmer is actually conducting it has very little current limiting ability.

I suspect that you may know all this Worth but I've spent quite a bit of time trying to explain that LEDs and fluorescent tubes are devices that you can't change the brightness of by changing the voltage on them and that they need some kind of current limiting. Then there is trying to explain not designing using typical specs, but minimum and maximum values.

[QUOTE=svalli;390750]. . . and the pure white LEDs should have plant friendly spectrum. Many of the LED plant lights are made for people who need to keep their plants in closets whole time, so I have a bit different needs, when I am using these just for seedling growth and not for bud production ;).

Sari[/QUOTE]

My understanding is that White LEDs are blue LEDs with a yellow emitting phosphorous
coating. What do you think of adding a yellow or more likely amber LED to the set up if you want to try more wavelengths?

I don't know how many of you reddit, but a member there has been working on an LED grow lighting primer, its taken him a while to get the first five parts posted but they're good reads if you're like me and thinking of making your own.

[URL]http://www.reddit.com/r/HandsOnComplexity/comments/1cuujk/led_and_led_grow_lights_part_one_heat/[/URL]
[URL]http://www.reddit.com/r/HandsOnComplexity/comments/1mk791/led_and_led_grow_lights_part_2_beam_angle/[/URL]
[URL]http://www.reddit.com/r/HandsOnComplexity/comments/1mk7gm/led_and_led_grow_lights_part_3_color_and_white/[/URL]
[URL]http://www.reddit.com/r/HandsOnComplexity/comments/1okfcv/led_and_led_grow_lights_part_4_building_your/[/URL]
[URL]http://www.reddit.com/r/HandsOnComplexity/comments/1rcgih/led_and_led_grow_lights_part_5_working_with_100/[/URL]

[QUOTE=Doug9345;390770]I'd say a typical dimmer switch that goes in a house generally won't work. They work by clipping part of the AC wave form essentially acting like a pulse width modulated power supply. With part off the AC cycle missing the RMS (for people that don't know what RMS is it's a type of weighted average) voltage drops. When the dimmer is actually conducting it has very little current limiting ability.

I suspect that you may know all this Worth but I've spent quite a bit of time trying to explain that LEDs and fluorescent tubes are devices that you can't change the brightness of by changing the voltage on them and that they need some kind of current limiting. Then there is trying to explain not designing using typical specs, but minimum and maximum values.[/QUOTE]

I was thinking of the old type dimmers not the new ones.

Somewhere in a box I have a pile of rheostats I used at work plus about a million resisters.

Why is it then that the LED lights I see at the store say they can be dimmed?

All of this talk is bringing up a sore subject with me.

When they wired this house a few years ago they didn't wire it from my opinion correct.

Only one hot wire going to the lights and ceiling fan so I cant just turn on the fan or light individually I have to use a pull string.:evil:
Then there is the one light switch in the hall instead of one at each end.
I can wire all of this but the ceiling is a nightmare to crawl in.

I am very interested in the LED stuff and am in the process of converting the whole house to it.
Grow lights are on the top of the list and want to suck up all of the information I can.

Worth

Worth,
We had similar problem in our house in WI. Originally we had just a ceiling fan in the cathedral ceiling of the living room. When we added a light fixture on the fan we added also a remote control, which allowed controlling the light and the fan and its speed.

Thanks posting those links lefolly. There is a lot to read and try to understand.:)

I believe I have to study this thing much more before spending more money on different color LEDs. There are so many opinions on different forums on the net that it is hard to find the real data on the issue. I just thought that the pure white LEDs could be good after reading a test made by one Finnish chilehead. He got much better results with pure white LED lamp compared to red/blue lamp, which had much more red than blue.

Sari

I've done a bunch of reading on LEDs and other lighting and the problem with much if not most LED information is that it is pure marketing hype with either no numbers behind it or numbers that don't correspond to what is being claimed.

One place that I go to find real numbers is here. [url]http://www.lrc.rpi.edu/[/url]

My only connection was I was a student there before my mom died and I ran out of money. This wasn't there when I was there but I believe that should be of the same quality as any of thier other programs their.


I'll post more thoughts later.

Sari years ago about 32 to be exact I studied grow lights from a source that was considered the guru of indoor growing and "tomato" cultivation.
His name was Ed Rosenthal.

What he said was the common bright daylight florescent bulbs at, at least 40 watts per square foot was what you needed and the grow lights were a gimmick.
He talked about the other lights like metal halide and so forth too.

He went on to say that flat white paint reflected useable light better than foil.
Sears was remodeling and I went to the construction dumpster and found all of the florescent fixtures I would ever need.
I also went to the store and bought a 300 watt quarts iodine light.

I wanted to grow 'Tomatoes" in my huge attic so I got some 2x4's sheet rock, nails plywood and flat white paint.

The "Tomatoes" grew like they were grown outside.
They were the talk of everyone but no one knew where they came from, it was my secret garden.:lol:
I learned a lot about container and indoor growing back then including cross pollination and developing hybrids.
Some of the first of the super tomatoes came from us guys.:lol:

I got worried about the garden and realized how deep I had got into it and how much I had to lose and pulled the plug.:(

Time moves on and the new LED lights are the talk of the town.

I have a young friend in Colorado that is growing "tomatoes".
He wants me to come up and do some consulting with a percentage of the investment.;)

Worth

My purple led lights have been in operation now for almost a week. I have pepper, dragon fruit, glory vine and purple bell vines under them. I have also same age pepper, glory and bell vine seedlings under a fluorescent cabinet light. When comparing the seedlings, the ones under the LEDs are not getting so leggy as the other ones and they have also bigger leaves. So based on just one week this looks promising.

I purchased some petunia and fuchsia cuttings yesterday and needed to set up a light for those. We have bought 10W, 4500K, 670lm LED flood lights from sale and I started to wonder, if those could work as plant lights. I did searches on the internet and found some information at the "indoor tomato" growers' forums about using those lights during vegetation phase. Based on that those could work for my indoor growing purposes. I have now one 10W flood light hanging above the flower cuttings. I may have to add more of them, but first I have to rig up a fixture to mount them on.

Sari

From what I can tell the big gain with LEDs is the ability to direct the light. I discovered how important not just brightness (power), but actually being able to direct the light onto the plant when I was using CFLs in brooder lights. The other factor is that an LED of the same power is smaller than a fluorescent so you can get a given area brighter.

If you go Google images and enter Smokemaster LED grow lights you'll see what he has done with LEDs. He's had good success growing hot peppers using 50 watt homemade panels.

I wish we had Nikola Tesla on this forum.:yes:

Worth

LED lighting has worked so well with plants that we have now built more of them. I ordered 10W cool white LEDs from Chinese ebay seller and my husband mounted two of them on the same size heat-sinks, which was used in our first prototype. I found perfect size aluminum plates for the 1W LEDs from recycling bin at work. We put 6 each of cool white, red and blue LEDs on the plate. DH built the drivers for them and added potentiometers for controlling each color independently. We needed DC voltage for powering them, so he built also a new adjustable power supply for me, since we did not have one with high enough voltage output.

[URL="http://s2.photobucket.com/user/svalli/media/ledlightsfromtop.jpg.html"][IMG]http://i2.photobucket.com/albums/y9/svalli/th_ledlightsfromtop.jpg[/IMG][/URL][URL="http://s2.photobucket.com/user/svalli/media/ledlightsfrombelow.jpg.html"][IMG]http://i2.photobucket.com/albums/y9/svalli/th_ledlightsfrombelow.jpg[/IMG][/URL][URL="http://s2.photobucket.com/user/svalli/media/powersupply.jpg.html"][IMG]http://i2.photobucket.com/albums/y9/svalli/th_powersupply.jpg[/IMG][/URL]

Buying ready made LED lights or at least getting ready made LED drivers could have been less expensive, but I can not complain since DH wanted to build all of this for my hobby.:yes:

Sari,
Hats off to you and your hubs. That's quite an impressive setup!

Very resourceful! What are the dimensions and watts total for your set-up? Thanks for the inspiration!

That adjustable power supply looks very much like mine (that I did not build). What output voltage/current range does it have?

Thanks, this has been a fun project. The heat sink is 1.5"x8" and has total of 20W LEDs. The plate is 8"x12" and has total 18W. Right now I have two of those heat sink kinds and one plate connected parallel to the same dc power supply.

The power supply can give out 10A at 30Vdc. There should also be a potentiometer for limiting the current, but he did not have one handy and I had a rush to get lights for my plants. The LED lights have current limiting circuits, so right now I have set the voltage at about 24V, which is enough to get the LEDs light up. The current we have going through the LEDs is not the maximum for them, so the real wattage may be lower than what LEDs are rated for. With just passive cooling we did not want to run the max current, since it could reduce the lifetime of the LEDs, when they run hot.

Sari

[QUOTE=svalli;402892]The power supply can give out 10A at 30Vdc. There should also be a potentiometer for limiting the current, but he did not have one handy and I had a rush to get lights for my plants. The LED lights have current limiting circuits, so right now I have set the voltage at about 24V, which is enough to get the LEDs light up.[/QUOTE]

I picked up my power supply from lab surplus, figuring it would be useful, but I hadn't until not found something specific that it would be useful for. The one I have can go up to about 40Vdc at 8A, and also isn't current limiting. I wonder if there's standard designs for these things that explain the similarities.

[QUOTE=Darren Abbey;403001]I picked up my power supply from lab surplus, figuring it would be useful, but I hadn't until not found something specific that it would be useful for. The one I have can go up to about 40Vdc at 8A, and also isn't current limiting. I wonder if there's standard designs for these things that explain the similarities.[/QUOTE]


Some of these standard numbers for things like power supplies likely go back to various lead acid battery combinations. 40Vdc is very close to what three 12v lead acid batteries would be.

Our one is made with 240V to 24V 250VA transformer, which makes the maximum DC output about 30Vdc. The rectifying power electronic circuit is my DH's own design an he also built the box by cutting and bending it from sheet metal. There is a heat sink, which sticks out from the back of the box (actually the whole back is the heat sink). I am quite amazed how quickly he was able to fabricate the whole thing. I guess he had to show me that all those tools and having his own workshop and electronics lab home is worthwhile.

Now I just have to grow some edible plants, to justify my hobby.;)

Sari

What is the current rating for each LED? This would tell me the resistance required at 24V DC. The circuitry would be pretty easy to do, but I don't have the tools necessary. You all did a great job.

Dan

The current rating depends on LED power. These are the 1W LEDs which we have: [URL="http://www.vekoy.com/UserFiles/File/PDF-liitteet2/OSW4XME1E1E.pdf"]http://www.vekoy.com/UserFiles/File/PDF-liitteet2/OSW4XME1E1E.pdf
[/URL] These are the 10W LEDs [URL]http://www.ebay.com/itm/10pcs-10Watt-10W-High-Power-Bright-LED-900LM-Bulb-10W-White-6000K-Lamp-Light-DIY-/231138229846?ssPageName=ADME:L:OC:US:1120[/URL]

Sari

I can't open the first link. Do you have a real data sheet for the second set of LEDs? It doesn't indicate if the values that they do give are minimum, maximum or typical values. It also doesn't indicate the spectrum which I suspect is important. I'd believe that the spectrum would e a mix off blue and yellow dies.

Still at $1.27 USD you could afford to cook a few to find out what their real specs were.

The first link was broken, so I fixed it and now it should open.

The eBay LEDs came packed in a bubble envelope with no specs with them, so only info is on that eBay page. we are not running the full 1A through them, because they seem to be plenty bright with lower current. My DH already burned couple of them, but I can not be angry to him since I paid less than 1 € for each.
We do not have any spectrometer, so I have just used a CD to see what colors are in the light and it seems that there are lot of blue, but also green, yellow and red. I would believe that the spectrum for these follows the typical curve shown for most cool white LEDs, where there is a high peak on blue and lower bell curve with high point around yellow. So far the plants seem to be happy with this light.

I found much easier way to build energy efficient LED grow lights than my previous projects with separate the LEDs. A guy from our office had ordered two super bright 5m flexible 12V LED strips from China. One was cool white and he did not need it for his home, so since cool whites work well with plants, I bought it from him. I cut the strip so that I can glue the pieces to 30x20cm aluminum plates. I soldered wires to power all the pieces and connected a 12VDC power supply to it. There was enough material for 2 of these panels. The strip uses about 14W/1m, so one panel is about 34W. The back side of the aluminum plate gets quite warm and is about 40°C when it has been on for few hours. To be extra energy efficient I'm planning to use the warmth to start my tomato seeds.

I have had one over some pepper seedlings and fuchsia cuttings for two weeks now and those are growing fine and have not become leggy at all. Today I built the second one to light my store bought flower cuttings.

Sari

Very neat project! I wondered how one used those LED strips.

About how much coverage would you guess you're getting? I've got four cool white LED bulbs covering about 18" x 12". And you know, it's never enough! :lol:

The panel is 8"x12" and when it is hanging about 10" above the plants the well lit area is about 15"x20". That is barely enough now.

When the season progresses and seeds start to sprout I have to set up also the other lights. I have now enough LED lights, so that I do not have to use the fluorescent lights at all.