The first step to this project is to get a simple hydroponics system up and running. This will let us get a feel for hydroponic growing and and what parts we might want to add sensors and control to.
After looking at a few systems online, I really liked the idea of using half a two liter bottle as the growing pot. I figured it would be fairly easy to attach the bottle to the reservoir lid using a threaded ring. I found this two-liter bottle cap start on Thingiverse that did the trick. With it, I was able to attach the bottles to the lids of a 6 quart rectangular container. Hydroton clay pebbles are being used for the growing medium. To keep the hydroton from rolling out, I printed this basket which fits perfectly at the bottom of the two-liter bottle.
The next challenge was finding a good way to fix the 5/16 ID hose to the top of the bottle. I originally tried to punch a couple holes and zip tie it, however the plastic was too flimsy. So I designed a rim that would fit on top of the bottles and has holes to tie the hose in position, pointed down at the plant.
Originally, I chose this self priming diaphragm pump. It was cheap and used a DC motor which would make it easy to control the flow. However, it was much too loud. So, I found another 12V submersible DC pump that could be placed right in the reservoir. This made the system super quiet and had a bit better flow. However this pump does not take well to variable voltage adjustment to control flow. For on/off control, the pump is hooked into a MOSFET switch and controlled by a Teleimperium microcontroller board. For now, I have a simple program that will run the pump for 15 minutes every hour. There is also a simple air pump to oxygenate the water, and a one wire temperature sensor.
I still need to program the controller to read the temperature and upload it to a server. Also planned is using a solid state relay to control the lighting. To monitor water quality, I am using a cheap EC meter along with a pH kit. For this crop of strawberries, the target pH is 5.5 to 6.5 and the EC should not exceed 1000ppm. Fox Farm liquid concentrate is the fertilizer being used, at a concentration of 2Tbs per gallon.
The next big challenge will be to develop a continuous EC meter that can be hooked into the Teleimperium so that data can be collected and graphed with Teleceptor. Automated pH measurement would be nice, but there may be issues with leaving a probe in the water at all times. We will have to research options.