If you love sprouts, this is THE way to grow them. It is fully automated, and all you have to do it put seeds in the trays, and the trays in the growing bin. Once they are ready, harvest, store, and eat. My sprouts have also grown considerably faster in this, than using a counter-top sprouter.
Currently I have only found one (commercially produced) automated sprouter on the market, and it costs ~$180 for just over 1sqft. of growing area. The growing area for this sprouter is ~4.25sqft and cost me ~$50, although I did have a majority of the parts in my garage. If you were to do this as conservative as possible I would estimate you could do this project for around $70 assuming you use recycled take-home (to-go) restaurant containers for seed trays and find a bin to do this in around the house. You could reduce the cost even further by checking garage sales for irrigation timers, and valves.
Step 1: Gather Tools and Parts
Parts you will need:
A bin with lid (I used one ~34" x ~18")
Mister kit (Orbit 20066 Portable 1/4-Inch Outdoor kit)
Irrigation valve (recommend 3/4" so you don't have to adapt it too much)
Irrigation timer (make sure it has at least 6 daily start times)
All appropriate adapters to connect your system to your specific water supply, and interconnect all components you choose
Whole house water filter (Culligan HF-150A, or Omni 0B1)
Carbon Cartridge for above mentioned filter
Calcium Inhibitor filter (WaterSentinel WS-21)
Razorblade / SHARP Knife
Drill and bits
Step 2: Install the Mister in the Bin
If you have spade bits they will work the best for cutting into plastic. I decided to install 5 misters into this bin, so I measured 3" down on the container on both sides, and drew a straight line end to end. I then measured the width of the container and divided by 7 (number of misters + 2 to account for NOT installing misters on the ends of the bin). For my bin this came out to be ~5", so I marked the center(only works if you use an odd number of nozzles), and then marked 5" increments on the line in both directions, then drilled holes. The bit size I chose was just right to allow the mister to be unscrewed from the "T" (it's socket) and reinstalled with the nozzle inside of the bin (and the hose outside).
After the holes are drilled remove all of the mister nozzles, and T-sockets from the water line they come connected to. You can do this by pulling back the retaining ring (may need pliers) and then cutting the line with a razor, and bending the hose to push the barbed connection out the side of the tube (as pictured). You can then use the remnants to reconnect these at the correct width to mount in your bin. Start from one end (considering which end you want the water line to extend from) and put a mister in. Attach one of the remnant pieces of hose (saliva, or water will help), and cut it to length to extend to the next hole. Connect another T-socket to this hose, and install the nozzle. Repeat these steps until you have all your nozzles installed.
Step 3: Install Drain Hole
I forgot to photograph this as I did it, but I do have pictures of the finished product. What I did was find a bottle around the house that had a ridge around the neck (as most plastic bottles do) and was an appropriate size to not only fit in the corner of the bin, but also fit a piece of tubing I had in the garage. This ended up being a nasal spray bottle (a 24-hour energy is a similar size). I removed the part that goes up your nose, and cut off the threads below the ring leaving it attached to the part with the threads (this is what you will use) Then find a drill bit that is a size the threads will fit through, but the ring will not. Drill your drain hole in the corner of your choosing. I recommend one of the front corners because you'll need to tilt the bin toward the drain, and you probably won't want it tilted away from you. You can then epoxy the threaded part of the bottle you used into the bin with the threads out (as pictured). you can screw on the cap to hold it in place, just be sure not to glue the cap on.
Now if you have a piece of tubing that fits on the threads, or you plan on just letting it drain into a pan below you are done. For my situation, my tubing fit on the cap, but not on the threads. To make this work for me, I just drilled a hole in the cap, and then slid my tubing onto the cap. This gave me a detachable piece of tubing from the bin that allows easy cleaning.
Now drain into something, or outside to your planter
Step 4: Connect to Your Water Supply
I chose to connect to my water spigot outside of my living room where I planned on locating the sprouter. You could also use a supply line tap under your kitchen sink, or in your laundry room, or just put a diverter on one of your faucets. Doing it like me will require you drill a hole in your wall.
Fit all of your parts together, starting with whatever you choose for your supply line, and finishing with a 1/4" high pressure water line connector. The sharkbite quick connectors are great for this.
My setup used:
1 male hose to barb
1 female 3/4 hose to barb
1 female 3/4 hose to 3/4 pipe
1 short 3/4 male to 3/4 male pipe
SPRINKLER VALVE ->
3/4" male to 1/2" female adapter
1/2" male to 1/4" sharkbite quick connector
1/4" supply line
Adjust yours accordingly
Step 5: Get Some Seed Trays
You can use just about anything for these trays. I have been using trays from a coutertop sprouter I no longer use, and some trays I bought online. You can also used "microgreen trays", whatgrass sprouting trays, or the plastice take-home containers you get when you get your food to-go from restaurants. Just be sure to drill enough small holes in them to allow adequate drainage. You can also epoxy on some little rubber feet (or some substitute) to get them off of the floor of the bin to help them drain. You only NEED two of them to slant the container in one direction, and give it drainage space.
The white trays pictured are available from http://www.greensmoothie.com/sprout/gogreen.php (the inspiration for this instructable)
Step 6: Program Your Timer
Finally, you're done. Now all you have to do is program how often you want this thing to turn on. I live in a very dry climate, and initially I had mine run 4 times a day at 6 hour intervals for 4 minutes. This worked fine, but sometimes my seeds would near drying out before the 6th hour. I would recommend watering at 3 hour intervals for 2 minutes, and you could skip some of the night watering. Currently I am watering at 6a, 9a, noon, 3p, 6p, 9p, and midnight. This is working well for me now. You may need to fine tune this for your climate, but it should be a good place to start.
If you need a place to get seeds, try sproutpeople.org They have excellent seeds, and selection, and incredible support for thier product. All of the harvest times for every seed/variety they sell is posted, and a lot of videos as well.
Be sure to leave the lid cracked open approx 1 inch when sprouting. You could probably put ventilation holes in the lid with screen glued over it as well, but I haven't tried it yet.