Instructables
Picture of Solar Powered 24 Hour Greenhouse
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You're probably thinking to yourself "Hey, isn't EVERY greenhouse solar powered?" To which you'd be correct. The greenhouse I've created is in fact a DOUBLE solar powered greenhouse in that it uses sunlight both day and night to help plants grow.

I live in Wisconsin, which is usually rather nice. Unfortunately Winter has been going full blast for months and shows no signs of letting up. For a mammal like myself, this kind of weather is annoying but not overly harmful. For my various house plants, however, this weather is quite deadly. Especially to the very small plants I'm trying to cultivate on my kitchen table.

To help my plants get a leg up on this weather I decided to build a greenhouse. The only problem is that a greenhouse only works part of the day when the sun is up. To give my plants a boost up, I'd have to throw on some grow lights which gets expensive and are overkill for my very small plants.

What I needed was a lighting system that turned on only at night. Not a tough task to accomplish so I decided to mix it up a bit and add an element of solar power to it. What I ended up with is a little acrylic plant incubator that runs night time lights powered by solar energy. (Just like the plants.)

Double Green Energy.

 
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Step 1: What You Need

Picture of What You Need
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If you need some solar cells you can grab the one I used at my educational electronics website BrownDogGadgets.com. Otherwise all these parts can be found at local Radio Shacks or Maker Spaces.

Tools

Soldering Iron
Solder
Scissors
Wire Cutters
Wire Strippers

Electronics

2N3906 PNP Transistor
1N914 Diode
5K Ohm Resistor
Red LEDs
2 AA Holder
2 Rechargeable AA Batteries
Solar Cell (I'm using a 5.5V 320mA Solar Cell)
Wire

Optional: Perf Boards to solder everything onto

(Or the super simple route of grabbing an old solar garden light and gutting it.)

Enclosure

Acrylic Cut Case
Silicon Sealant
Rubber Bands

(Or going the super simple route of using a 2 Liter Soda Bottle cut in half.)

Don't you ruin the plants exposing them to 24 hours of light?

genius4hire3 months ago

Use the neared resistor value of 5.1K available everywhere element 14 or Jaycar.

rhino79799 months ago
Does anyone know where to get a 5k ohm resistor?

http://www.parts-express.com/5k-ohm-10w-resistor-wire-wound-5-tolerance--016-5k

If you absolutely have to have a 5k ohm resistor, take two 10k ohm resistors and connect them in parallel. The resistance of two equal value resistors in parallel is equal to half of one of them.

JoshuaZimmerman (author)  rhino79799 months ago

Use a 4,700ohm resistor. That works just fine as well.

very interested

Does it work? I would have swapped out 2 red LEDs for UV LEDS for the added uv light for the plants. Nice project though!

rhino79799 months ago
Can someone help me I built the circuit but only a few of the LEDs barely came one when I covered the panel??? I did have to wire 5 1k ohm resistors in series to Acheive the 5 k ohm resistance and the batteries were fully charged any suggestions? Did I screw something up?

It's most likely that the voltage is not high enough, or it is not high enough for the resistor you have chosen. Put some numbers in here:

http://led.linear1.org/led.wiz

Typical forward voltages are listed here, but you can measure it with a volt meter to find your exact voltage:

http://en.wikipedia.org/wiki/Light-emitting_diode#...

JoshuaZimmerman (author)  rhino79799 months ago

This is the problem I ran into. If you're using a bunch of LEDs make a simple Joule Thief Circuit. You'll get full power out of the LEDs then.

Or rip apart a solar garden light and use it's built in joule circuit/ dark detecting. I'm planning on completely redoing the circuit part of this project. I'm not pleased with the power output at the moment.

bobsmith6529 months ago

How much did they spend researching what colour of light plants like? I could have saved them a load - it's not green! They reflect green!

As for the joule thief, it will take the batteries down to a really low voltage. If you take a rechargeable below a certain voltage (1V for NIMH I think) you can damage them.

The joule thief won't get you any more power from the batteries though, you can only get out what you put in with the solar cell. Going from 30% full to 60% full is the same as going from 0% to 30% full, but going to 0% would damage the cell. As an example, the Prius batteries are kept between something like 40% and 80% to extend their life.

If anything, you should really have a low voltage cutoff when using
rechargeables, but the LEDs will stop working below a certain voltage in
this case, so it is not necessary.

The solar cell is most likely your capacity limit in your project.If the battery is the weak point, you would be better off getting higher capacity batteries, or putting another set in parallel .

Do your batteries get up to 1.4v per cell before lighting up time? If not, they are not full.

rhino79799 months ago
Thankyou I ordered one and will add it to the circuit I think it made it to "messy having the extra resistors so I'll clean it up and try again thank you!
rhino79799 months ago
An now it's not lighting up at all
BurgersBytes10 months ago

If you are interested in Joule thieves, I have the perfect circuit for you. The circuit inside of that solar garden light! Here are some circuits using one 4 legged chip with one 56 uH coil. http://petesqbsite.com/phpBB3/viewtopic.php?f=4&t=...

The chip is capable of working with batteries up to 5 volts. I also cover other projects in the thread. If you need the chips, email me.

JoshuaZimmerman (author)  BurgersBytes9 months ago

Yeah, I should have gone with a Joule Thief. The sad part is I even have a pre made PCB for a Joule Thief (from a different project I'm working on) that I could have easily used. I'll probably swap it in later on. When I do that I'll update this project.

dbyrd2610 months ago
does moisture cause any issues to the circuitry? I suppose it would depend on humidity levels but just curious :)
JoshuaZimmerman (author)  dbyrd269 months ago

All the important stuff is outside the case. I'm sure after enough time the LEDs would suffer, but I'm not concerned. Outdoor solar garden lights are often pretty "open air" about their circuits, and they can last for years in rain and snow. If someone was super concerned about their LEDs they could alway use a sealer on the back of the PCB board. It's probably completely unnecessary in such a simple project.

1tri2god10 months ago

Hi Joshua, It was nearly a decade since working on my bio b.s. in uni, but perhaps some more discussion on how most plants require a dark cycle for proper photosynthesis, nutrient enrichment, and overall ability to mature? The plants you wrote about closer to the ice caps have adapted over a millennial stretch to a reduced need for the night cycle. Might a list of popular species' genus (/geni?) be helpful to make this project more successful for those wishing to try it? Just a thought...

On a whole, very nice work!

"Genera," to geek out :D http://www.archives.nd.edu/cgi-bin/wordz.pl?keyword=genera

JoshuaZimmerman (author)  1tri2god10 months ago

I know Alaska grows a lot of typical "winter" crops rather quickly in summer.

I will most certainly do some more research and post it here if I find anything.

I was mainly thinking that this might be helpful as a "plant ambulance" or an incubator for new seedlings.

pculbert10 months ago

Joshua,

Thanks so much for this 'able. Every winter I try to keep some Cala lillies alive in our townhome. We don't have any southern exposure so the poor things really suffer. It never occurred that this could be done with LED's. I will get on this first thing Saturday. Cheers!

lynnfiorante10 months ago
Plants don't like having sun all day they only need 12 hours or they will be unhealthy get bugs and die

It is a known fact that people often suffer from lack of light in the Winter, so maybe it will help the owner care for the plants better? How could you possibly know that plants will get bugs if you have never tried Joshua's suggestion?

JoshuaZimmerman (author)  lynnfiorante10 months ago

How would they get bugs in a closed system inside?

Spontaneous generation.

godbacon godbacon10 months ago

Possibly from the soil. you could nuke the soil, or go hydroponic.

lynnfiorante10 months ago
Trust me I have a indoor system and many other indoor plants and if a plant is unhealthy the bugs will find it even in the middle of January I just got rid of spider mites and its -30 outside just let your plants have 12 hours that is all they need for light they don't like hAving more thAn that
steamer55110 months ago
If you want flowers (like an African violet) use red LED's. A combination of 1red to 4 blue works great.
steamer55110 months ago
For growing non-flowering plants (herbs, lettuce) Use blue LED's. If you
JoshuaZimmerman (author) 10 months ago

One thing to note here is that in Wisconsin in winter time we get at best six hours of cloudy sunlight. Very very poor growing conditions. Adding in extra light helps in 100 different ways.

I've done a whole lot of google searching and everyone has their own opinions about doing 24 hour light. It's always a massive debate. 24/0, 18/6, 12/12. A lot seems to be just opinion or based on the type of plant you're doing.

Also keep in mind that LEDs are no substitute for real sunlight and isn't giving the same output. Who knew seedlings were so much work!

kimbutterfly10 months ago

great

jabujavi10 months ago

Could it better if you use UV and IR LED's? I saw similar projects with these type of LED's

JoshuaZimmerman (author)  jabujavi10 months ago

From everything I've read the only LEDs you really need to use are red and blue. And really it should be 10 red for every blue you use. Those are the wave lengths that work best for growing.

+1 for what JoshuaZimmerman said. You won't necessarily increase the plants' ability to grow, since your bound to hit a point where the growth rate plateaus. Rather, if you avoid wasting energy producing light in the 475-625nm range, less of the light will be reflected by the chlorophyll. So, while it might not make the plants spring up much faster, your greenhouse electrical will be more efficient.