Put that wasted computer time to good use by growing a plant. I know that you often procrastinate when you should be working...we all do it...looking at Facebook, at Instructables, watching YouTube and all of the other things that we do when we should be working.
Actually I developed this project for a workshop that I was asked to give in Pori, Finland during December of 2016. I based it on similar objects that I am experimenting with in my own work for my Master's thesis. At the end of this Instructable, you should have a small terrarium where you can grow a plant using LEDs which will use your computer as a power supply.
If you keep your USB Powered Plant on your desk and plugged into your computer, all that time you spend working, procrastinating, watching cat videos and learning how to do stuff will be also used for growing a little plant in its own ecosystem.
This whole project should take 1-2 hours and is based on the research which NASA has done on growing plants using artificial sources of light, there are links and further reading/research located at the end of this Instructable.
Step 1: Tools & Materials
- a utility-knife / stanley-knife / carpet-knife / box-cutter
- a soldering iron
- a hot glue gun
- a multi-meter
- wire cutters
- a wire stripper (optional)
- a solderless breadboard (useful but not necessary)
- a 1.5L or 2L bottle
- a drainage material (I used lava-rocks but you could use rinsed gravel, river rocks, marbles, etc)
- potting soil
- 4 red LEDs and 1 blue LED (10000-15000 mcd / Millicandela)
- a small PCB
- a USB cable
- a small plant with roots or seeds
Step 2: Terarium
The first step in this project is to cut your 1.5L or 2L plastic bottle into two parts. Plastic bottles come in many different shapes, so try to use one which you will be able to cut so that the two pieces naturally fit together.
I originally used a mineral water bottle which had hippy curves, cutting out the hourglass shape allowed the top to sit snugly onto the bottom and create a closed space. I also tried this with a Jaffa bottle which had a long conical top. Using the most common shape of bottle, if you cut it about 1cm below the bottom of the cone, you should be able to squeeze the top onto the bottom.
There are a lot of bottles laying around, so try to find one already used instead of buying a new one ;)
Step 3: Planting
Fill the bottom section of your bottle with 2-3cm of drainage material. I used lava rocks but you could use stones, washed gravel, marbles or some other material which will be fine to sit in water for a long time. Plant your seeds or your small plant in 4-6cm of potting soil.
Step 4: USB
Cut the mini or micro end off of the USB cable, strip the outer insulation so that the wires are exposed and remove about a centimeter of insulation off of the black and red wires.
Step 5: Cut Your PCB
You will want to cut your PCB to about the size of a bottle cap so that it can accommodate your 5 LEDs. Cut a square with 7 or 8 holes in each direction, by scoring the PCB using your utility knife (don't cut yourself!) then break it at the seam with your pliers. Use your wire-cutters to cut the corners of the square to make an octagon.
(see the image for what the result should look like if my description was confusing)
Step 6: LEDed
To power your LEDs correctly you will need to wire the red LEDs so that they are all running in parallel and then connect them in series with the blue LED. The cathode of the blue LED will connect to the anodes of the red LEDs.
I suggest that you work out this step on a solderless breadboard before soldering everything to your PCB. See the schematic, diagrams and photos for further illustration.
Step 7: Power-Up
Melt, drill or poke a hole in the bottle-cap which is the same diameter as the USB cable. Run the USB cable through the hole so that the exposed wires come through the bottom. Now solder the positive (red) wire to the anode of the blue LED and then solder the the ground (black) wire to the cathode of the red LEDs.
Make sure that the circuit works by plugging it into a USB port. If it does, then hot-glue the PCB to the inside of the bottle-cap. If it doesn't, then check your circuit and troubleshoot for issues.
Step 8: Finish and Further Reading!
Screw the bottle cap onto the top section of the bottle, water your plant, place the top section of the bottle onto the bottom section and plug in your USB cable for a working USB Powered Plant!
Now you can put all of that computing power to good use by growing a plant which is living in it's own ecosystem and photosynthesizing while you spend time on the computer.
Check out some of these links to read more about using LEDs for growing plants:
LED Grow Lights: An Ultimate Guide for 2016
You can see more of my projects at the links below: