It has been two weeks since my last blog post. In that time I have done a ton of research, and changed my original design a bit. Instead of using PVC pipes for an NFT system in the main grow area, I will be constructing a system of stacked trays built on a wooden frame. These will mostly be flood and drain trays, but I want to also experiment with low pressure aeroponics. There are many reasons for this change. The biggest reason is that it will allow me to fit more plants in a smaller space. It will also be less complex. An NFT system requires a different outlet for nutrients in each channel. Flood and drain requires only one for each tray. This system will also be easier to insulate and heat in the winter, and it reduces my reliance on PVC as a building material. I have read a lot of conflicting information about the possible health and environmental effects of PVC in hydroponics and aquaponic systems. While I haven't reached a concrete conclusion on this subject, I think there are compelling reasons to move away from this material if a reasonable alternative exists.
I will be concentrating on this aspect of my grow system first, and if time permits, I will move on to nutrient mixing and the germination and seedling chambers. Unfortunately, I will not be able to spend nearly as much time as I originally had planned on this contest. I am going to do one part at a time so that I will have at least one aspect of this design completed and functional.
I also lost a bit of time cleaning up the horrible mess my garage has become this summer so that I have some room to build my system. Below is the space I have to work with. On the left is the seedling chamber I used for all of my starts this spring. It was basic temperature and humidity control using a Moteino and BeagleBone Black running OpenHAB. It served it's purpose for one spring, but it was never intended to be a permanent solution. Actually it was all just thrown together from stuff I had lying around.
Here is the BeagleBone Black with a cape I made for wireless communications through a Moteino. The Moteino acts as a gateway for the 915MHz network. Other Moteinos are scattered throughout the house and garden. I will be using the same BeagleBone with the new system. This time data will be read through USB or Ethernet into OpenHAB.
Here is the wooden frame I have built for the flood and drain trays. There is a large reservoir at the bottom that will hold the hydroponic solution and 3 pumps. There will be 3 trays above the reservoir for plant growth. Each section will be 2'x4'x3.5” and will hold 3” of media. There will be 2' of height between shelves. Each tray will be covered in pond liner. Two trays will be filled with growing media and that will be flooded and drained at regular intervals. The third will be used for experimenting with aeroponics or some other method that will not require media.
I started building the trays and the lighting on one level. I have done this as inexpensively as possible mostly using materials I have lying around. What I have to use is several daylight spectrum and warm red CFL bulbs, Y-sockets, socket to plug adapters, and a roll of mylar. Mylar is thin, fairly inexpensive material that reflects more than 90% of light. The first thing I did for the lighting was drill four holes in the center support for the socket to plug adapters.
Then I drilled holes to run the wires through for the lighting, covered the top in mylar, and cut holes in the mylar where the holes were drilled. I soldered wire to each plug and ran them through either side of the center support. Then I screwed in the Y sockets and secured them to the center support with zip ties, and tested it out.
With a few CFLs plugged in...
And.... let there be light!
I have used a similar lighting setup in the past with pretty good success. It is the cheapest lighting solution I have come up with and is suitable for seedlings, salad greens, and small herbs. I am pretty sure this is the lighting I will be using for the next two levels, but I may decide to experiment with LEDs as a supplemental or primary lighting source. I am currently exploring using the LED kit that was supplied to build a grow light, but it seems like it would be very time consuming to solder all the LEDs required to provide adequate light, and I don't want to put money into having a PCB fabricated, stencil made, and then throwing it in the reflow toaster. If I have time(my biggest problem), building by hand may be worth it because LEDs are most definitely the future of indoor cultivation. The increased efficiency and lack of waste heat are huge advantages in indoor agriculture. I also like the fact that LEDs can be run on relatively low voltage DC instead of having 120VAC running beneath trays containing water.On top of that, the narrow beamwidth of LEDs means that I would not have to surround the grow area in reflective material. I do have a couple of TI TLC5971 LED driver ICs that I have had sitting around for over a year without using... maybe I will see what I can throw together.
I have ordered the pond liner I will be using for this project. It is a 6'x10' roll of 20mil HDPE made for aquaponics systems. From what I understand, HDPE is food safe and a great alternative to PVC. I am researching the bulkheads I will need for each tray, and trying to decide on how I will pump the water. I will either use three different pumps, or one pump with three electronically controlled valves. One problem I have found is that inexpensive valves require pressure to be activated, and I do not know if the pump with produce adequate pressure. I may just use three different pumps to keep things simple.
That's all for now. I'll post more next weekend.
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