# LED grow lights - DIY?



## Safado (Jul 10, 2005)

I will be following this thread carefully. Thanks for the work you put into this so far. I am very excited to see the results.



DarkCobra said:


> In
> What about other components? We need a few resistors to limit current, a small perfboard to solder the LEDs into, and a small section of PVC piping or a plastic box to mount the circuit in. We can seal the circuit with polyurethane, or cover the assembly with a piece of clear polycarbonate. Finish assembly with some glue, assorted mounting hardware, and hook-up wire. We also need a power supply, a $10 surplus laptop power supply will work great and power quite a few clusters. Minimum toolset includes a hacksaw, a drill, a soldering iron, and something to snip the LED leads. All this stuff can be obtained locally at your hardware store, Radio Shack (or equivalent), and used computer store (for the power supply).



I have looked around for where to buy a few of these items, and have found a few questions about others:

Laptop Power Supply: Ebay

Resistors: Can you give a little more detail on this? In the past I designed my DIY project to wire the bulbs in series, just so I don't have to deal with resistors.

Perf Boards: These are available all over the internet. Here is one example.


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## DarkCobra (Jun 22, 2004)

Hehehe.. Believe me, I know all about Ebay and All Electronics, and I'm poorer for the knowledge.  B.G. Micro is great too; they've got some really nice, cheap, and compact laptop power supplies right now; as well as perfboard, resistors, etc.

As for the resistor. If you look at LED specs, you'll see a forward current (If) for recommended operation, and also the forward voltage drop (Vf) for that current.

For example, a LED might say If=20ma, and Vf=2.5v. Which means that if you feed it 2.5v, it will run at 20ma. Perfect.

If you put four of these in series, the Vf for the chain is now 10v. If you feed the chain 10v, it will run at 20ma. Still perfect.

But what if you have a 12v power supply? That will drive four LEDs past their spec. You could add a 5th LED, but then they're running under their spec - better, but not optimal.

Instead, we can put a resistor in series with the LEDs. The value is calculated like this:

R=(Vs-Vf)/If

Vs is the power supply voltage. So for our example:

R=(12-10)/0.020
R=100 ohms

In case R calculates to a non-standard resistor value, use the next *highest* value. Big illuminators like what we're proposing typically use several series chains in parallel. Each series chain must have its own resistor. If one of the LEDs should short out for any reason, the resistor also gives some protection to the remaining LEDs in a chain.

If you want more info, here is a good FAQ on using LEDs.


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## BOTIA (Dec 23, 2003)

Interesting thread.
I found a thread on another forum where somebody did an extremely detailed and logged experiment using 1 watt luxeon star leds. Very expensive but very efficient. 
Here is the thread it is along one but a great read.
http://www.aquaticplantcentral.com/forumapc/showthread.php?t=1009


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## DarkCobra (Jun 22, 2004)

Thanks, Botia! I just read it.

One comment caught my attention on page 7 from defdac, who calculated the PUR (photosynthetic usable radiation) of the Luxeons from their spectrum:

_"This means you would need apx 7-8 times as much watts when using Luxeon Stars compared to an efficient T8-bulb like Philips Aquarelle (0.8 microEinsteins per Joule) to achieve the same growth-rate."_

The Aquarelle is a fluorescent plant-grow light that focuses its output at wavelengths plants can use - just like our propsed LED cluster. So our 2W Ruby cluster is likely equivalent to at least 14W of white Luxeon LEDs for plant growth; and Gomer demonstrated that the Luxeons were slightly better at plant growth per watt than regular lighting!


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## Wasserpest (Jun 12, 2003)

I think LEDs will be the future of many lighting applications... not just truck taillights. 

I am interested in the outcome too. The only comment I want to make is that while hitting the exact spectrum for your plants is good for them, think about the people too... maybe mixing in some white LEDs would still be a good idea.


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## Safado (Jul 10, 2005)

Wasserpest said:


> I am interested in the outcome too. The only comment I want to make is that while hitting the exact spectrum for your plants is good for them, think about the people too... maybe mixing in some white LEDs would still be a good idea.


I agree 100%, but I can think of a few interesting ideas...

A few blue lights on 24X7 as a moon light

White lights on during prime viewing times (6:00-8:00, and 19:00-22:00 for me)

Blue and Red (optimum spectrum) 8:00-17:00

As I think of my tank I am wasting a lot of light (unused spectrum). I am only in front of the tank a little bit each day. It would be nice to be able to control the lights of each spectrum separately, though I imagine my fish wouldn't like it much.


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## DarkCobra (Jun 22, 2004)

I must confess that I will not be building these for my own tank.

Sure, I'm interested in LED grow-lights out of scientific curiousity. Low energy consumption per unit of plant growth is a given. You might also be able to better grow plants without algae, control internode distances, induce blooming, etc.

And I figured enough people might be interested in the science, or actually building them, to warrant me doing a writeup from an electronics geek's perspective.

But I love the look of a brightly lit, accurately colored, planted tank. So I'd have to build a combination hood - red LED clusters for plant growth, fluorescents for me. I think white LEDs are still too expensive to replace fluorescents for normal viewing, except on pico tanks.

Sometimes I will just sit and watch my tank. I have a folding chair tucked away next to it for that purpose. Other times, I'll just pass through the room; and when I do, I *always* take a look. How could I not? This little 10 gallon of mine has become the room's focal point. It's a living, breathing, changing work of art, that I had a hand in creating. Each time I look it raises my spirits a little. I think having to flip a switch to see the tank in normal lighting would take away from that experience.

So I'm passing on the LED grow-lights for now. However, I will continue to provide info and answers to any questions posted.


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## jimjim (Nov 9, 2003)

*LED lights for tall tanks*

Hi All: Being in the electronicly challanged group, I can't help but wonder about the use of LEDs for say 25-29" tall tanks. I know you can use these to focus on dark areas, but would'nt this be usable for say Moss walls? Is 18" the limit of penetration? Could you determine which red and blue LEDs just to grow say, moss or alge(cladaphoria) (I know my spelling is bad) just where you need it?.....Help! this sounds like a cure for bad areas of large tanks also...Jim


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## nik (Mar 7, 2006)

This thread seems to have been lost, but I chose this one because my questions are probably mostly for DarkCobra...

I have decided to try this. I've just built a small tank, about 6 gallons. Right now it's lit by 3x20 watts halogen (!) downlights. This is probably barely enough to keep the plants alive...

Anyway, it seems like people here are focusing on the chlorofyll absorbtion wavelenghts, 470 and 660 nm. I understand this in regards to photosynthesis. However, running an HPLC-test on spinach we of course get peaks at a lot of other pigments to. Won't these have any effect on growth / health of the plants?

And my real question; could you give me a hand with the calculations of neccesary LED's for this tank? I'm thinking about getting LED's from www.besthongkong.com . They have a lot of different ones here. How important is the mcd?

I will eventually, if everything works, use white LED's too, to get rid of all other lights. And I do plan on having small clusters of LED's on different variable resistances, so I can, say, control the red and blue individually.

Any advice appreciated 

Oh, btw, hi all. My fist post here


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## DurocShark (Feb 6, 2006)

The highest reds I can find are 630nm. Where are the 660's? Blues are easy. The besthongkong.com link has more vareity than my usual vendor: lsdiodes.com

But neither have that 660nm red. 

I'm thinking about spotlights with these on more difficult plants, while using fluorescents for general tank lighting.


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## endparenthesis (Jul 13, 2004)

LEDs grow plants excellently... they just aren't cost-effective yet.


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