Getting Started

I'm not a farmer. Never even really interested me. What does interest me is conserving our environment, reducing the amount of energy/water we require to live a comfortable life. So far my experiments/interests have been primarily in energy (electricity) and electric vehicles. However, one post on KeelyNet about portable farms using aquaponics got my attention and then somehow lodged itself at the back of my head. On March 5, 2009 we (monica and I) went to visit a farm in Auroville, south India. After a tour of the farm, which uses sprinklers throughout, we were shown the 'hydroponics' experiment that they had been doing. Gino (the guy working there) explained to us that using this technique you would use less water and grow more in the same space. We had an empty bird cage at the entrance to our house and somehow this got us motivated. So the next morning we drove into the city and bought a whole bunch of stuff.
I won't go into depth about hydroponics here since all the info is any on the web, but what we wanted to do was to use the NFT (nutrient film technique) to circulate water through a system of channels.

Here are some pictures that will show you how we built the system.


4" Pipes ready to be cut


The bird cage, and two 200 liter barrels


The pump (0.5 HP) that will circulate the water


Top view of the barrel with float in it


The tank with float level Pipe from roof Barrel on the roof


4 drips, using adjustable flow rates for each channel


Outlet to collect water and cycle it back


How it works

The water sits in two barrels. When the lower barrel is full, it switches on the pump and the water is moved to the top barrel. Using gravity, it runs down the pipe and drips out of the drips into each channel. This has the effect that water is oxygenated and is constantly running. The water collects at the end of the channel and runs back into the lower barrel. The lower end of the channels needs to be higher than the top of the collection or 'sump' barrel.

I developed a small electronic controller and used a standard float ball to take care of the pump's cycling. If anyone is interested I can post the schematics. Going to make a PCB for this too but still did not get around to it.
The basic idea is that a pot (5k) is connected to the float and the analog value tells me the water level, it's pretty precise. I have a small microcontroller (16F676) and two buttons to set the max and min levels. Then a small relay that switches on or off.