I built this using recycled / free materials wherever I could think to. It cost significantly less than $100 in total. Here's what I used:
Omron G5LE-1 relays]
1 A.C. extension cord
1 A.c. power cord
1 A. C. outlet
The watering system:
1 Tiny clean-water pump
1 Plastic milk jug
~2 Old road bike tubes
1 Milk crate
The lighting system:
1 4' fluorescent light fixture
1 "plant type" fluorescent bulb (I used the Ott-Lite
, but any bulb marketed as for plants should be fine)
The soil moisture sensor:
2 galvanized nails, 1-4" in length
The light sensor:
The temperature sensor / alert:
1 LED (any you'd use with an Arduino will do)
1 10k-ohm thermistor
The plants and holders:
A variety of seeds, preferably that'll grow into things you'd like to eat. Everywhere, I hear people recommend swiss chard as an easy starter plant...
As many plastic milk jugs as you'd like. I used ~30.
28-gallon clear plastic storage containers. You'll need one for every 6 milk jugs.
~5 red bricks for each storage container, or anything else that will allow the milk jugs to stand at least an inch off the bottom of the container.
I used Mel's Mix, the mixture recommended in "The Square Foot Gardener."
It consists of 1/3 peat moss, 1/3 coarse vermiculite, and 1/3 mixed compost, with the mixed compost coming from at least 6 different sources. I've heard lots of people bash peat moss and vermiculite's sustainability (not to mention vermiculite's obscenely-high price), so definitely explore your options here. As I understand it, you want something w/:
-lots of plant nutrients (the mixed compost)
-water retention (peat moss / vermiculite)
-'fluffiness:' soil should be light so plants can easily grow their roots through and you can easily remove plants from it (vermiculite / peat moss)
Tools / Miscellaneous
3 ~10k-ohm resistors
1 ~210-ohm resistor (for the LED)
several feet 22-gauge wire
(in my case a Duemanilove, but any should work)
1 Protoshield (Ladyada's model)
1 mini circuit board
Hot glue gun, with glue