Aeroponic Vegetable Garden

From Professr's Lair

Premise

Due to the current economy, I'm left wondering how long I'll be able to procure sustenance. So, I looked into home gardening solutions.

The whole soil/weed/fertilizer/pesticides thing is just unnecessary and difficult to deal with in an automated fashion.

So, the logical step is hydroponics. Since it uses liquid instead of dirt, it's easier to clean up after and maintain. Since it's indoors, there are no bugs, weeds, or plant diseases. Finally, with the right setup, it's easy to automate, since you can control a liquid environment much more easily than a solid one.

Progress

1/10/10 - Added an automatic nutrient reservoir and a tank-cleaning pump

There are about 20 tomatoes growing, with the largest so far the size of a half dollar. They're still green.

10/16/09 - Grow light arrived, tomatoes now have 4 leaves (including the cotyledon)!

I've got two tomato seeds sprouting! Hopefully my grow light will arrive in time, as they need lots of light as soon as leaves appear.

I have ditched the bubble aeration system, as I'm told aeroponics, while more complex, is far more efficient. It uses a smaller nutrient reservoir, so I save $$$ on fertilizer, and apparently it is better for tomatoes than my previous design.

I bought everything except a humidifier and the control electronics from Walmart.

• 1 plastic tub with lid
• 1 submersible aquarium pump with air intake
• 1 empty pepsi bottle
• 2 aquarium plants (for their pots)

The aquarium pump sucks water from the bottom of the tub and pushes it into the bottom of the pepsi bottle (through a small hole). It pulls air in at the same time, mixing it with the water for oxygenation.

The pepsi bottle has had the top removed (from the top of the label up), and the spinning-disk atomizer from the humidifier sits in it. The atomizer is screwed to the lid of the plastic tub, so only the water intake part of it is sitting in the pepsi bottle.

When the pump is on, it raises the water level in the pepsi bottle to the atomizer intake. The atomizer is turned on for 5 seconds every few minutes via my controller, and it sprays a fine mist all over the inside of the tub. I've cut holes in the lid and press-fit both aquatic plant pots, and they get sprayed quite nicely when the atomizer is on.

First Attempt

I've got a 25 gallon fish tank set up with an air pump and large bubble bar (to provide oxygen for the roots). Most systems use an ebb and flow design, where the nutrients are pumped in to bathe the roots every 15 minutes or so, but bubble aeration works well too, and doesn't involve pumping large amounts of fluid around to multiple tanks. The temperature inside the house pretty much varies from 68 to 74, which is definitely *not* within the optimum temperature range for *any* of the plants I want to grow. Tomatoes, for example, like temperatures in the low 60s, and cabbages etc. want less than that. This would be much easier to provide if the house temperature wasn't *higher* than the desired temperature, because then I could just use a tank heater (many are commercially available for cheap). So, I have to come up with some method of refrigerating the tank's water.

My solution: a "brain cooler" project I did a few years back. It uses the Peltier junction from one of those cheap mini-fridges, connected to a computer water-cooling kit. The kit pumps water in a circle, cooling off a heat block (designed for a graphics card) at the end of the tubing. This will pump heat out of the tank, hopefully getting it at least 10 degrees cooler than room temperature. It's a lot of water to cool off, though, and I'm not sure it'll work with just convection currents in the water (there's no pump, so water doesn't really move a lot in the tank except by bubble action).

I finally got the Peltier junction working properly. At first, I had tried placing the watercooling block in the tank, without realizing that it had parts on the outside that could rust. Now that the block is ruined, I'm using an aquarium pump to circulate the tank's fluid through a series of tubes connected to the cooling block bolted to the Peltier junction. It's slow, but it does cool the tank off, and right now it's sitting around 10 degrees below room temperature.

Next step is to get a long heat sink and bolt that to the junction instead of the cooling block. That way, I can just dip the heat sink into the aquarium pump's water reservoir, which will allow a much higher water flow rate than those tiny rubber tubes, hopefully cooling the tank off faster. Right now it takes all night to cool down this much, so rapid temperature corrections are not really possible. I'll also have to buy another PicAxe and a digital thermometer chip for it, so I can actually control the temperature in the tank with some accuracy. I don't want the roots to freeze or overheat.