Friday, July 17, 2009

Germination Station Part I

I have been working on this project all spring, and I am finally getting around to posting about it.  Unfortunately, it did not turn out to be as successful as I would have liked it to be.  A couple of  years ago, I created a PID controller that controlled the soil temperature of a Biodome.  Now that we own a home, I was hoping to be able to add a bunch of other variables.  The variables were the following: soil temperature, air temperature, light, and moisture.  I also wanted to have Xbee units to relay the information back to a Webserver so that I could view the system's status from the web.

The  Xbee idea had to be postponed because 1 of my Xbee units got toasted.  As a result, I had to be tethered to the project via a USB cable, and that caused some technical and logistical problems.  I still got a lot done, but in the end, the entire system did not work.
The Structure:
The base: I wanted to see how much of the deck it took up.
The side supports. I will expand upon my rationale for this shape later.
I attached two fluorescent lights as part of the support structure. They were also the most costly part of the project.
Additional supports and hinges so that I would be able to easily lift the cover.
Cover attached to the base
You can see that I did not line up the cross supports. The whole structure was not as stable as I wanted it to be, which may have been responsible for water flow issues.
Plastic covering
I took a 4" by 4' PVC pipe and cut it in half(horribly) and glued it together. Attaching it to the structure was very precarious, and I will need to think this out better the next time around. The pipe was to funnel water into the trash can. The plastic that was connected to the "roof" of the pipe was very leaky, so it did not work as efficiently as it could have.
Electrical Systems
Wiring the Lights
I took a basic extension cord and cut the end off, then wired the lights in parallel together.
Electronics (Arduino and Open Squid)
I planned on using the Arduino again. I had an extra one on hand, but I didn't need to use it for the system. It was useful for debugging basic code at lunch, though.
Open Squid
I needed to control multiple AC devices (hair dryer, heating pad, and lights).  Last time, I hacked a digital AC timer.  That would have been a little too costly this time.  I found the relay squid by Liquidware, but it was a little out of my price range, and I figured I could build one cheaper.
Got these from Mouser.  Really cheap.  Just cut the ends off of them.  Time for some soldering!!!
I spent a good 2 hours working on the circuit in the top left corner, and it just would not work.  I found out that the relays that I had picked could be driven with just the output current of the Arduino. (After examining the Atmega and relay documentation, the relays should have blown out the IO on the board, but for some reason that did not happen)  I am working on redesigning the circuit now.
I wired the ground and neutral straight through to all the plugs and switched the hot.
Soldering the AC lines on the board was tedious. I am surprised it all worked.  I put some hot glue down to protect the connections and keep everything in place.
All done! Time to get it in the box (project box from radio shack).
Everything hooked up to the Open Squid.
I have created a schematic in Eagle with the correct transistor switching circuit.  I have laid out the PCB, but I want to do some testing of the circuit before I ordered the PCBs.  All the schematics and gerbers will be available after I do a system test.
Next time, I will go into the Sensor Stalk and the Arduino program and the problems that I ran into while working on this project.


/Life2Death/ said...

That power setup looks 100% ready to start your house on fire. Combined with the leaky roof...

omibrosa said...

Those are going to be some awesome tomatoes come december if all goes well!:)

Primos said...

Anything new?? :) How about potatoes?