Introduction: Self Watering Terrarium From Clear Totes
I LOVE to make homemade pizzas! My favorite is a Margherita with fresh Basil. My efforts at making pizzas is always challenging when Summer is over and fresh Basil becomes scarce or expensive! I'm cheap!
Basil is an easy plant to grow in the summer but Basil thrives between 80-90 degrees Fahrenheit, need lots of root growth room, and MUST have at least 6 hours of sunlight-- or they will "bolt," bud/flower and perish shortly thereafter. Some enthusiasts try to keep up with plucking the buds relentlessly but, "Aint nobody got time for dat!"
With the LED technology and Arduino technology available to us today, creating a better environment for plant growth is easy.
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Step 1: Things You Will Need
1. Drill with step drill bit, 3/4 inch speed drill bit, and smaller bits for nuts and bolts.
2. Tablesaw and masking tape-- to cut plastic without cracking it.
3. Hot glue gun (optional-- I used it because it was easy on low pressure water fittings ,but may not be useful for higher water pressure. Con: It looks rigged and "ghetto.")
4. Soldering Iron (optional)-- you may want to just use a breadboard and be done with it.
5. Pliers with Wire Cutters
1. Two large, cheap, and clear plastic totes. -- Walmart $5 each-- and possibly a smaller one for a water reservoir (see 14).
2. 6 to 12 small bolts and nuts to hold tubs together and optionally place hinges.
2. Masking Tape
3. Handles and/or hinges (optional)
4. A small ceramic heater with thermostat. I bought one for $10 at Walmart
5. LED Grow Light with timer--I bought a 24" flourescent fixture at Walmart. You should be able to find a timer easily as well.
6. Arduino UNO
9. 5mm LED (optional)
10. NPN transistor( I used a 2N3904 but a 2N2222 may be a little more resilient as it handles a wide array of variances -- The 2N2222 is a tough little bugger!)
11. Old, used washing machine water fill solenoid. ( This can be picked up from an appliance repair shop as these things go bad all the time. A standard washing machine uses two of these-- one for hot and one for cold. Most of the time they are joined together -- hot and cold. One will go bad and the other is totally fine. I sawed the two apart and separated them. Most are 12v driven, but some are 120v AC. You want the 12v solenoids, if possible. Mine is rated at 3AMP but I put a 1.5 AMP power supply on one and it functions well. )
12. 12-volt power supply
13. Fish tank tubing
14. A way to supply water to your washing machine valve. I used a Female Hose thread to 1/2 inch MPT (Male Pipe Thread) adapter. I used a conduit nut and washer with rubber washer to secure it into a hole drilled through a container reservoir. MPT fittings are slightly tapered to seal as they are being screwed in. A conduit nut will fit all the way to the base of the taper without tightening on the thread itself. See section named water reservoir. If you have a rain barrel outside, or you want ot hook you r terrarium to an actual water line, and you want to use the water to water your plants with a hose to your terrarium, you had better be confident that there will be no failures with an entire tank of water on your floor.
Step 2: Create Your Tote Terrarium
I did it this way and because it was super inexpensive and I was able to use some old stuff.
I initially looked for a clear plastic trash can but couldn't find anything that was cheap. Because -I'M- cheap, I went to Walmart and bought two identical clear plastic tubs, less than $5 each. I discarded the lids and placed them top to top.
I wanted to be able to open the terrarium easily and be able to take plants in and out so I needed a large opening. I decided to cut the top tote lengthwise and hinge it on the bottom. I had the hinges lying around and a set of cabinet handles as well. I'm not sure what the cost is if bought new but I'm sure some tape and a knob of wood or something would work just as well.
CUTTING the plastic tote was simple but make sure you use a high RPM saw. Use a piece of masking tape and run it from one end of the tote to the other as a cutting line. If you use a jigsaw or handsaw your results may vary as these plastic containers are made of brittle plastic that tends to split, crack, and shatter. I used a high RPM tablesaw and it cut very smoothly. Try to steer clear of cutting the corners or regions around the handles of the tote as these areas are designed to give the tote strength. If you DO get a crack, use a heat gun (careful with distorting the plastic), or press with an iron between two pieces of parchment paper to mend. Hopefully you won't have to go there. I used small bolts and nuts to bolt the two totes together.
After the tote was complete, I drilled a 1-1/4 inch hole in the back for the heater cord, and water supply tubing.
Step 3: Place the LED Light
My original design used a small LED array on the end of a goose neck. This worked for over a year until the power supply for the LED array burned out.
I switched to the less expensive LED bars that can be bought at the local Walmart for less than $14. The light bars are an improvement in two ways. Firstly, the light is broader than the single point of light, delivering a much better coverage inside the tote. Secondly, the light bar is close enough to the top of the tote, it reinforces the saggy plastic-- making it much better.
Step 4: Create Your Water Reservoir
Your Basil plants need plenty of water when they are in their happiest 80-90 degree environment.
The Water Reservoir
Most plastic containers that I found have angled sides, tapering towards the bottom. Try to find a container that has the least amount of angle on it. The container I found still has a slight tilt when I mount the solenoid, but it's negligible. Be creative and find something that is pleasing to the eye as well. If you CAN, have your pottery friend whip up the perfect decorative watering reservoir with a prefabbed 3/4 inch hole for the valve... I found that the plastic container in the picture above worked well because it was easy to access inside for tightening the washer and nut.
Safety First-- time for leather gloves and goggles.
I have used this technique to secure valves on rain barrels without a problem. The seal is strong and should last for years.
You'll need to use a rubber washer. I created my own from a sheet of gasket material and a high speed drill bit. To make your own, clamp a sheet of rubber gasket material to a 2X4 or a scrap piece of wood. Make sure when you are cutting the gasket material the drill is revved up to a high enough speed. Push the drill slowly at a high revved speed and your gasket should be very smooth. If the the rotation of the drill becomes too slow or you try to push the drill too quickly, your gasket material will be mangled on the inside. Once the inside is cut (drilled out), you can use scissors or clippers to cut the outside.
Since you will have your drill out, mark the place for your hole in the reservoir and create the hole for the valve. I placed the wide electrical washer as far down the outside wall as it would go, and marked it with a sharpie. Once again, rev your bit high and push slowly to not crack the plastic. I used a stepper bit for this hole, checking to make sure the plumber fitting would easily fit into the hole. NOTE: Do not try to screw the fitting into the hole. It will crack the plastic. dirill the hole just a little bigger.
Once the holes are cut, fit the pieces together in the hole as shown above.
Now, you can attach the valve.
Step 5: Place Your Ceramic Heater
Just put your ceramic heater in-- easy enough... but wait! Make sure you adjust the thermostat!
Something about putting a heater inside a plastic enclosed tub is wrong, right? I would suggest making sure your heater has enough clearance to circulate air well and plug your system into a GFCI outlet for safety.
There are planter heating pads available at nurseries that are waterproof and made for this type of application but as long as you're giving a modest amount of clearance, you should be good. The heater should be able to heat the small terrarium in a matter of a few seconds and will switch back off.
Step 6: Set Up Your Arduino
I used an Arduino to create this watering system. I soldered all of the components together and wire tied the wires, and hot glued for stress relief. First I would use a breadboard to make sure that everything is working properly.
Here is the code for the Arduino. More than one hygrometer can be used but this code is just for a single solenoid. The jist of the code is to have the sensor turn on every eight hours and check for water. Important: The prongs on the sensors are easily corroded in soil if placed on a continuous charge so I have it switched off until needed. If watering is needed, the time needed for watering is deducted from the eight hours so the eight hour mark should be --at least a little more-- accurate. For larger projects, I'm sure the 1/2 inch tubing would have been fine, but the stiffness of the tubing wouldn't allow me to place the end in the tubing into the plant easily. I wanted more flexibility, so I used fish tank tubing-- perfect! Attach the relay-switch to the 12-volt supply of the flow solenoid.