A little side project one weekend turned into a novel idea! The wife left the sprinkler
on all day for our garden by mistake so she asked me to automate it. We already
have the following hardware...
The only thing missing was a rain sensor like the
Orbit Wireless Rain and Freeze Sensor for Sprinkler Systems
which we have
used in the past. Then it hit me! There are shortcomings of these hard-wired rain
sensors (besides the investment)...
- Mounted to the house they won't be accurate from all directions
- No output of dryness level (only a water or don't water switch)
- No input of sprinkler water received (unless you mount it where it gets hit)
- They will allow the sprinkler to run even during rainfall
- No input of weather forecast data (percentage) or per-storm rainfall totals
- Decent brand with freeze sensor and adjustable soil permeability is over $30.
A personal weather station like the
Vantage Pro2 Plus
can cost hundreds of dollars but would give us the accuracy
we are looking for.
So I set out to create a Virtual Rain Sensor. A program that gathers information
from personal weather stations for the past number of days (configurable interval
and weather location). It then runs a variation of the Penman-Monteith algorithm
to calculate losses through transpiration and evaporation based on sunlight, wind,
temperature, relative humidity, barometric pressure, elevation, and regional reference
surfaces. We then apply the gains through rainfall from mother nature. It also pulls
the forecast for the next day and the average per-storm rainfall total for the current
day and calculates a predicted rainfall total for the next day.
Taking all this into consideration (and whether the current observation or forecast
low is at or below freezing) we calculate the duration of our watering based on
our inches per hour calibration (using a coffee can in your garden you run the sprinklers
for an hour and then measure how many inches of water you collected). We turn each
X10 zone on for the calculated duration and then we turn it off again.
The application runs as a service on any Windows operating system (XP or 2003 Server
minimum). Based on each zone's configured interval it will download a small packet
of weather data from our servers and make a decision. The details of this decision
will be recorded and viewable on your dashboard
This is currently a "beta" program so there are undoubtedly bugs. I have set up
the dashboard so you can monitor and configure most aspects of the operation. Participants
in the "beta" will retain their accounts for an indefinite period free-of-charge.
Please report any problems and feel free to make suggestions or requests
or check the status of an existing issue