[conspire] Watering automation: an edge case cautionary tale

[Rick Moen]

Quoting Paul Zander (paulz at ieee.org):

> Since OpenSprinkler is open source, you could, in theory modify the
> software so the green house gets watered on a fixed schedule
> independent of rain.

There's a less-convoluted way.

I have that perfectly fine Rainbird 8-station 'dumb' controller left
over, lacking only a power cube (that I stole for the OpenSprinkler
unit).  It can get reconnected, controlling water to solely stations in
the greenhouse, and not connected to the rain sensor.

None of this is actually urgent, as I think consecutive rainy weeks with
almost no sunny days is unlikely.  But I'm bearing the matter in mind
for future work.  Another greenhouse-specific need currently going unmet
is automated watering for seedling trays.  In the past, I've relied on
everyone's good intentions for manual watering, with very mixed results, 
i.e., lots of dead seedlings.

Getting an additional water feed _to_ the greenhouse is part of that
bundle of problems, which bundle includes fixing the halfassed current
water distribution.  At present, we have garden hoses going under concrete 
paths and then connecting to solenoid valves, then going out more garden
hoses to drip hoses.  It's all scarily bodged together and one hose leak
away from turning half my yard into a pond.  Much of tht ought to be
entrenched and upgraded to galvanised pipe.

And you know, one really can't pile much work onto an Arduino, because
it's an astonishingly minimal computer.  Its big advantage isn't ability
to support significant software (it can't), but rather good analogue
interfacing abilities.  For anything complex, you'd want a real computer
(say, a Raspberry Pi or better) sending instructions to the Arduino over
TTL signaling.

There's a _lot_ of information out there about how to do practically
anything (as to analogue interfacing, anyway) with an Arduino.
Originally, I found myself deep down that rabbit hole:  I think I was
reading an ingenious explanation of how to use simple household
materials (like, a nail and a bit of bell wire) to make the Arduino able
to monitor the level of moisture in the soil around a particular plant,
when I realised I was in danger of spending the next three months
designing and building hardware -- whereas, I really just wanted an
assembled and working controller and working, off-the-shelf rain sensor.  
So, that was when I mail-ordered an OpenSprinkler unit and bought a rain
sensor from OSH -- so that it would Just Work[tm], but be hackable if I
needed that.