Introduction: Battery Powered LED Grow Light

About: Please support and share our mission; the Plant Doctor is a non-profit, open source online research laboratory specializing in electronics+plants. Our vision is to bring together nature and technology in a sim…

please support & share our mission;


new design;The Plant Shelf
new design;The Plant Arm

So how exactly do I make one of these arms?

Today after work I decided to make a very simple version so we can all understand it better. If you have all the parts laying around, the whole process takes about 30 minutes, including soldering times. the only part you probably won't have at hand is the LED light, but don't worry ebay can take care of this problem.

Let's start with explaining the lights better, this part took me the longest to research, the rest is basic electronics.

Now you can solar charge it too! - Solar Charge your LED grow lights

Step 1: High Power LEDs

the future of lighting. these extremely tiny devices can create incredible amounts of light. there are couple of things to know before starting any project with these LEDs.

how many lights do I need? - also the spectrum

how am I going to power them?

how am I going to cool them?

1. how many lights do I need? - through out my research I have seen successful attempts of people using a single 3W led light and getting the same results as with a 23W cfl light bulb. but another interesting thing that I have found is that when growing plants all that they truly need is only 1W leds, anything less is not enough and anything more is just wasted energy per area i guess. this does not need that you can grow a huge tree with a single 1W led. what it means is that you should use lots of these 1W leds but aimed carefully at different angles, exposing all parts of the plant to the light. since these lights create very little heat, they can almost touch the leaves. another thing to watch for here is the spectrum of light choice. for the vegetative stage we need 5000K-6500Kelvin spectrum (430nm in LED talk). since my design is very small, and I just have a single plant training it to be a bonsai citrus tree, in my case all I should need is this single 1W light. I get very limited direct sunlight at my apartment, currently from 11am to 6pm, instead of 6:30am to 8pm if the plant was outside, so I am losing about 6-7 hours/day direct light. IF I had no sun at all, I would then add two 430nm 1W LED (blue) + one 660nm 1W LED (red) for this stage of the growth, the plant is about 1.5yrs old. I would eventually switch it to 660nm only even maybe and get some lemons :)

2. how am I going to power them? this is when we get technical with resistors and volts etc. KNOW your LED power requirements before fixing things in place for sure. go to eBay, search for 1W 660nm LED. click on any of them, usually sold in 10packs for about $8.00 USD. click on the item description, it will tell you some information like this;

forward voltage: 2.5-2.7V

forward current: 350mA

spectrum: 660nm deep red (every seller posts this info).

now we can calculate how much power we need. In this design I am using a single 1W 430nm high power LED, the settings on it are, 3.2-3.4V @350mA. I chose to power my design with 3 x 1.2V rechargeable AAA batteries hooked up in series, adding upto 3.6V. so I have 3.6V coming out of the batteries into my maximum 3.4V LED. """ important """ you do not want to burn out your LEDs, they are cheap but it takes too long for them to arrive here at america. so now we need to talk about resistors. please read all these links before going any further.

- LEDs for Beginners;

- Basic Electronics;

- Wiki grow lights;

--- IMPORTANT: Everybody please make sure you have read at least introduction to electronics. Know your resistors and know the Ohm's law (use a calculator to be safe: ) - Look at many other designs, get familiar with what you want to do, SKETCH IT first, always be extra prepared and have fun !

assuming we all have read all that, which you really REALLY should, we can go on...

3. how am I going to cool them? you will see during your research that people have heat sinks and fans attached to their LED lights. I am not an electrical engineer, I can solder and can design extremely basic circuits (just getting into all of this). I am an artist, especially a musician but I love designing things. so when you give these tools to an artist, he will most certainly deny the fact of cooling these LEDs because let's face it, all of those fans and heat sinks are too big and ugly. I have been testing with LEDs for a while now, always attaching them to the perforated metal hanger that you see as the arm. This bendable metal hanger is the perfect instrument for my design. It is very slim, strong and is full of holes which dissipates heat very fast. please check out my other design here; in this version I have 4 x 1W 660nm LEDs. that was an earlier prototype which was covered in electrical tape, not anymore, now I know exactly where the cables/resistors go, so the metal is actually completely bare, the wire is just fed through the holes. you can see it clearly here as well; . IF you were making a larger LED light, let's say connecting 20 x 1W LEDs, then most likely you will need to cool it down with a fan and a heat sink, but I know that all this is going to change very soon as the technology advances, I mean these lights already are upto 100W per single LED, size of a coin. that equalls to 900W incandescent style bulb !!! from the tip of your finger tips.... another important thing I have to mention here is that LEDs do not like change in current, that is why when you want to make a more serious grow light, you will need a device called LED Driver. they are very cheap and sold on eBay as well. so for example, if I had 20 of these 1W LEDs connected as 2 x 10 in series, I would need an LED driver that supports 3.2-3.4V x 10 = 32-34V @350mA then connected in parallel adding up to, 32-34V @700mA. search on eBay for 2 items, 430nm 1W LED, once you find the one you want, look at the specs, do your calculation then go back to eBay, search in this case 32-34V @700mA LED driver, buy both items, hook them up, add heat sink + fan. you can have a VERY cheap homemade plant light. they have gotten incredibly cheap

next step....>

Step 2: Secure the Arm

pretty basic step here, get 2 screws, shape the perforated metal hanger and then cut to size. this thing can be cut with heavy duty scissors from a local hardware store OR even better, if you bend it back and forth at the desired length, concentrating on the same area while doing so, after about 20-30 bends it will just snap off very clean cut. making it extremely easy to work with.

if you are starting with an empty plant pot, you can use bolts and nuts to secure the arm. in my case the plant was already grown, so I just screwed it in, make sure your pot is plastic, I don't think you could do it on clay without breaking it, maybe some other method can be used for that. maybe wrap the hanger all around it in a loop...

Step 3: Glue the LED

don't actually use glue please :) I use metal epoxy, it is probably the best solution for this example. what you need to do is get some metal epoxy from the local hardware store ($4.00). use sand paper to scratch the back of the aluminium plate on the LED as well as where it will be glued to on the arm. this will help epoxy to work better. mix the epoxy on some loose paper with a chopstick or toothpick, do not get it on your skin, its not very runny, its like honey, you should be ok. place a decent amount on the back of the LED, if it is thick, it will fill any uneven surface area, which is what you want. hold the LED in place for at least 1 minute constantly blowing air to it. the description on the epoxy says that it sets in 5 minutes and cures in 24hours, but you will see yourself that since the LED weight practically no weight, it instantly sticks to the arm, without you even holding it up there, just like honey would do :)

you could add several LEDs at different lenghts/angles, penetrating the plant much better, as I did in my other designs.

ok next...

Step 4: Wire the LED

before we even think about how to connect the LED to the power source, we have to get wiring to and from it. so get some 22" wire and measure it from the base of the plant to the LED, going with the metal wire, times two wires for both the negative and the positive.

I love how they set up these LEDs. if you look at it closely, you will see that for both the - and + there are hooks :) so make some hooks on your wire as well and hook them up together, check it out, now you can just carry the LED this way and what's even better is that this rig will work without soldering :) in this current design I actually didn't solder the wires to the LED, they are just "hook-ed" on there, hehe... (it's all about simplicity, right )

I choose USB ports in my designs for its functionality and being globally accepted. I can travel with my design to India and it will work instantly, no converters, no attachments etc. I treat the ports as a means of delivering power, no data, not yet at least - we will be adding a webcam option too very soon !


Step 5: Testing and Soldering

ok now we can begin to see some action,

for this design I needed 3 x AAA (1.2V each) batteries adding upto 3.6V in series. again, my light was 3.4V at max, so I need a resistor. the local dollar store or the thrift store are the best places to find options to fire up some LEDs. I had a battery holder that I took apart from a mini desktop fan from the dollar store, which ran on 3 x AAA. you can not get all these parts from Radioshack or eBay for this cheap. this battery holder already had on it an on/off switch and a resistor, which I calculated to be close enough to what I needed. using the LED calculator; we see that I need a 1/4W - 1ohm resistor. from the color band on the resistor that was on the battery holder, I see that it is 8.2ohms 5% it is more than I need but it is better this way, otherwise your LEDs will burn. this is why we need an LED driver, because this device has built in chips that regulate the voltage and the amperage, keeping it always the same. my design is very basic, but you can easily modify it to be very much more powerful.

I have added the 3 batteries, touching the wires from the LED to the battery pack, we see that the light comes on. it may not be working at its full potential, but as you will see that at this power, that LED is lighting up surely bright, NEVER look directly in to it, as you will realize that it hurts, hurts bad ! just don't make direct eye contact with them and you should be ok :) after all we are all very new to these crazy lights.

basic stuff happening here, the red and the black wires are exposed. solder them all together now. eliminate the other colored cables you will find inside the usb cables. those are for data transfer.

Step 6: Finished View

here you can see that we have a beautiful, healthy plant with a usb cable sticking out of the back of it

it is now ready to accept power from any source you may have around that is in line with the requirements of the LED. weaving the 22" gauge wire through the existing holes of the metal hanger, we are left with a very clean and sleek design.

Step 7: Attach the Battery Pack

I rolled the extra cable in a loop and sent it through the arm, so it is hanging on there carrying itself.

dim the lights, and turn it on. it is actually much more bright than you see in the pictures. you will see yourself once you put one to use.

in the background you can see my other design, my plant shelf unit, I was lucky in this design that my 2 x 660nm 1W reds require 2.5V @350mA, so two of them add upto 5V @350mA - a perfect match for a USB power source. USB 2.0 offers 5V and upto 500mA, I read that the USB port on computers give away only the requires mA, this theory seems to be proven when I connect my shelf to my laptop, at first for a split second, the light shines brighter and dims down... this may hurt the LED in the long run, during that split second of brightness... but I have been experimenting this way for a while now but nothing has happened yet to my LEDs. experiment at your own risk...

you can also solar charge your battery pack, as I show on my other post here;

Solar Charge your LED grow lights

PLEASE be very careful with any electronic device, circuit. do not get hurt, take your time, don't rush and be kind in the comments,

also please add on to my design, take it to the next level, i want to see some other designs emerge, please add a webcam module, arduino controlled watering + sun sensor, solar charging.... I have all these planned but work takes too much time, I do this during my free time and again, I have no previous experience with electronics really. I really can't wait to learn using the arduino. thanks to this webpage, everything seems easy now, just lots and lots of reading :)

love & peace

Gardening & Homesteading Contest

Participated in the
Gardening & Homesteading Contest

Gadget Hacking and Accessories Contest

Participated in the
Gadget Hacking and Accessories Contest

Green Electronics Challenge

Participated in the
Green Electronics Challenge