Since winter seems to be nearing its end here in St. Louis – after what seemed to be a longer one than usual with lower lows and more snow than I can ever remember getting over here, it felt good to make it back over to Warren Street to check out the project site.  A few weeks ago there was a team of people who hung up a bunch of decorative flags on strings.  While I found out about the event too late to attend, it looks great!

Sunflower+ StL Site: Spring 2014

Electrode Removal & Inspection

In preparation for Season 2, the team is preparing to till the plot over and to account for that, we went over there today to dig our electrodes and wiring out of the ground, so the entire plot can be made-over at the same time.   We found that removing the “super-electrodes” as we called them to be much easier than putting them in the ground.  After locating the wires, we pulled upon them until we found each electrode.

Electrode removal

Then it was a matter of digging till we found it and using a pair of pliers to pull them out.

We were curious how much the electrodes corroded over the course of the extended season, from April to March, almost a full year with about 1.5-3 volts across them the entire time.  Of course the amount of current flowing through the electrodes varied drastically depending upon how damp the soil was, not only across the entire region in general, but also at the sites of each individual electrode.  This can be seen by looking at each of the positive electrodes (the really rusty ones in the image below).  Some were minimally corroded, while others were corroded down by more than 2.5 inches!

Electrode corrosion & degradation since April 2013.           (Top 2 were positive, bottom 2 were negative)

The top-most one that we’re referring to here was actually located at the very front of the plot where the soil was incredibly hard and rocky. My guess is that most of the corrosion occurred when rainwater water pooled up against the bottom of the rod because of such limited drainage over there. Most of the electrodes across the rest of the plot corroded more or less the same way, probably due to relatively equal drainage characteristics (except for the far back where the ground got very rocky again!)

Buried Electronics Need To Be Fully Waterproofed!

When we went to the back-left of the plot to check on our microcontroller-driven region, we found a water-logged container with our rusted-up electronics inside.

Waterlogged & rusty mictrocontroller electronics

The big lesson learned here is that anything set underground has to be completely water-tight! It’s obvious, but we figured that most water would drain quickly (we placed the device in a hole dug out of soft soil). We placed our connection port holes high enough so we didn’t expect any water to get in… Yet we were wrong. A lot got in and ruined our electronics, batteries, and wiring.

For the brief time it did work, from late fall till who knows when, it seemed to operate in the usual characteristic manner as can be seen by the electrodes below:

Electrode degradation from October 2013 to March 2014 using time-varying voltages.

If you’re new here and want to learn more about the Sunflower+ Project StL, go to the Electric Fertilizer Sunflower+ project page. In the meantime, stay tuned for more posts covering Season 2!