Finally have some lawn data

Having run the system for about a month, and fixing a few problems here and there along the way, I finally have a few days worth of data from the lawn, and some results.

My current setup is thus:

1. Water trigger point set at 25. When one of the sensors hits 25, we fire off the appropriate set of sprinklers.
2. The sprinklers run for about 10-12 minutes each to give a good deep soak.  One sensor triggers a pair of sprinkler rows on either side of the sensor.
3. The script runs once every 3 hours to check the sensors. It takes about 30-45 minutes after watering for the water to drain into the soil, and soak the sensor.  Running the script out of cron every 3 hours seems to be about right.

First, the pretty graph:

Lawn data.  Set point 25, 3 hour cycle, 18 days.

In the graph above, we can see the 4 sensors, and in blue, we see the sprinklers.  The tall blue spikes are the lawn sprinklers, the little short ones all over the place are just the drips, so ignore those.

 And of course, the second result, being the lawn itself.  I've noticed a very slight browning from this watering schedule.

I've also noticed in the above graph, that it seems to take two watering sequences to drive the sensor down.  If you look closely, you can see before each dive in the sensor, there are two blue spikes 3 hours apart.  I believe the lawn is getting too dry in-between waterings, and it's taking alot of water to backfill. This is especially true for row 3, which seems to dry out the most.  Perhaps in a future edit, I will run that row's sprinklers longer.  Looking even closer, it looks like row 3 never triggers.  Apparently row 4 triggers and I think row 3 is just getting overspray.  Row 4 seems to have the steepest incline of the 4 slopes post-watering.

Due to all of the above, what I've done now is set the trigger point down to 21.  I'm hoping this provides better results.  I'll have to run it for another week or two to find out.  In some ways, this is a very interesting method of programming, as it takes 2-3 weeks to find out if your code changes work or not.

Writing code to interact with nature turns out to be much more challenging than having it interact with a computer.  Fun stuff!