I had a bunch of stuff for this project lying around my house already and only needed a timer and adjustable drip heads which cost me about $10 for both. Using your imagination plus some help from google to re-utilize or re-purpose things lying around the house can make this project a lot cheaper. I wanted to make this system low maintenance, low cost and low interaction. The solar panel I am using may be a bit small for this project but from my calculations I should be able to run it indefinitely or for a very long time without needing to charge the battery. From what I calculated I should be able to run the pump for 10 - 30 seconds each hour and with the flow rate I tested on this pump that should plenty if not more than needed to soak the roots and then give them time to air out. To get the most out the pump I am using airline tubing.
Step 1: Materials Needed:
1) Large storage tote - lightproof if possible / if not you can paint it, coat it till light won't shine through the lid or tote.
2) small 12v pump found on ebay or Amazon from china
3) 12v battery ( I used a 7ah SLA, I pulled it out of a battery back up for a computer)
4) 12v Solar Panel (I had a small one that plugs into a car cigarette lighter)
5) Solar charge controller, can be found on ebay or amazon for around $10-12.
6) 4x 3" net cups, I printed mine out using a 3d printer.
7) Substrate (you can use lava rocks, pea gravel, clay pellets, or a host of others, your choice on this)
8) cheap chinese12v cycle timer $6 - 15 on ebay or amazon I used GERI FRM01
9) 3x airline T connectors
10) Airline tubing, preferably black to avoid algae buildup
11) Water soluble fertilizer (choice is yours on this as well depending on the plants)
12) Water Proof container big enough for battery, charge controller and timer.
12) adjustable drip heads
13) if you want you can use a power supply and small charge controller instead of solar and plug it into a 110v outlet or even skip the battery and charger, though if you experience a power outage your plants wont get watered.
Step 2: Setting Up the Tote
Let me start out by one very important rule, roots dont like light, also algae growing in your nutrient solution is going to have a bad effect on your plants ability to grow at their best and in your tubing will clog the water flow...
Ok, get one of your net cups and trace out four holes in the lid. Cut carefully so the lid doesn't crack. You want the net cups to drop in freely but not fall through the holes or leave gaps where light can shine through.
Once your holes are cut, drill four small holes for the tubing...use black tubing as this will stop algae from clogging your lines. I used the connectors that came with the adjustable drippers and superglued them to the lid. I used clear tubing inside the bin and black outside. You can use all black tubing if you like.
I will likely trim the length of the tubing down. The less tubing you use will increase the flow rate. Make sure to cut all tubing equal lengths or you will get different flow rates from the drippers. I attached the pump to the tubing but I will have to solder more wire on to the pump and increase the length.
Step 3: Setting Up the Battery, Solar Panel and Charge Controller
Wire your battery to the battery terminals of the solar charge controller. Wire the solar panel to the solar charge controller's solar panel terminals. The load will connect to the timers power terminals and to the pump. Refer to the included pictures for basic wiring reference.
I used separate wires for pump and timer from the load terminals of the charge controller. One wire feeds the timer, the other feeds the pump. On the pump's power wire I cut the (+) wire and ran it into the timer's relay terminals. As its set now the pump kicks on for 15 seconds every hour...this is just a rough guess at this point, I'll have to readjust the settings by monitoring the plants.
I found a great set of instructions for the timer on thingiverse.com, just search for FRM01 Timer Relay Module.
I realized the timer has a reset function while setting it up, that can be controlled by a relay so I decided to try to find a way to add a moisture sensor. I found a moisture sensor relay on eBay for $4 I plan to attach to the timer. At a later date I'll post an instructable on that as well.
Just a suggestion at this point, use a long 6' length or more wire to your solar panel. You want to be able to place it where it will get the most direct sunlight every day...as for the box containing the battery, timer and controller....you will want to find a spot that is in the shade all day...nothing kills a battery dead like heat, and the heat from direct sunlight will definitely shorten the life of the battery.
Extend the pump wire as well so it will reach out of the tote and into your plastic battery box. I soldered extra wire to the pump, used silcone on the connections then shrink wrapped it to waterproof it. I used a clear $3 snap lid container for the battery/electronics box from WalMart. I will be placing something over the box to keep it shaded. I picked a clear box so as I am working in the yard I will be able to see the charge level LED's on the charge controller and the LED's from the timer so I can see at a glance that all is well with the system. As my solar panel is a bit small I may need to swap the battery and recharge it periodically, hopefully not, but we will see when the plants are in it how much they need the pump running.
I ended up installing a switch and 10 amp fuse between the battery and the charge controller just for safety and ease of operation.
Step 4: Finishing Up
Fill your net cups with your chosen media, I'm using rapid rooter plugs surrounded by lava rock filler. I have noticed the rapid rooter plugs retain a lot of moisture, hopefully combining the two will prevent needing the pump to run a lot. This is something I am just guessing at this point and until it's set up and running I won't know for sure. It should be pretty easy to dial in with the ability to adjust flow rate with the drippers and by adjusting timer settings.
Mix your fertilizers in rainwater, distilled or reverse osmosis water...if you absolutely have to use tap water, use a de-chlorinator like those used in aquariums. For young plants use one third to one fourth the recommended dosage per gallon. Use enough water to last at least a month...you will need to dump out the water and mix a new batch every month.
Carefully place your seedlings so they stand up straight in the medium. Place the drip heads close enough that the water will hit the roots.
Step 5: Final Notes
I added a sponge pre-filter on the pump after reading about how much drippers like to clog.Make sure to squeeze the sponge under water, I didn't and the pump sucked enough air out of it to stop working...took a couple minutes to figure that one out, lol. Had to happen right as I was trying to demonstrate how it works to my fiance. She got that look on her face that she gets with my projects that says "Ummm, yeah....ok then".
I printed out some tubing stakes on the 3d printer to position the drip heads. The timer has a low power mode that I enabled. The system as I have it so far, puts out a nice stream of water that should fully soak the rapid rooter plugs. I am planning on adding the plugs and filling the net cups this weekend when I will have time to monitor the system for initial settings.
This system for me is just a stepping stone to see if the process is viable and so I can dial out any problems before I build a PVC system where I will likely re-use a lot of the parts from this build. I will be adding a soil moisture sensor soon but that will be another instructable.
The tote used will eventually degrade and become brittle here in the FL sun, so it's definitely not a long term use item. It should last long enough to let me beat the learning curve and be able to grow some nice plants. When it comes to a build like this, there are so many variables that need to be adjusted, tweaked or changed depending on your setup, your pump, the plant's needs, the properties of the substrates you use, timer settings and your local area weather. My settings are purely guestimation at this point, and until my seedlings are ready to go into this system and I can narrow down my parameters there won't be much more info.
Thanks for checking out my build and I hope it generates some ideas and help on your builds...Good luck and have fun!!!
Step 6: Update Week One
Set the timer to only water 15 seconds every 2.7 hours.
Plants in the back row sprouted on their own, front row are transplants from seedlings that were doing rather badly in soil on their own...front tomato on the right was wilted and half dead at 9am, this pic is from 7pm...already the stalk is strong and leaves perking back from being wilted.
Last two pics are the very healthy sprouts from original planting...strong stalks and leaves... Multiple seed sprouts...the two that didn't sprout were likely bad seeds, as a test I transplanted soil sprouts that weren't doing well...so far, system seems to be outperforming soil with no intervention from me...it is taking care of itself better than I could.
That almost spells success, more updates to come... Can't wait to upgrade this system to a much larger operation...
As with all scientific experiments, need to follow through all the way. More updates incoming.