hplato – I personally calculated runoff time by watering and watching and it is on a per-zone basis. My mulch-filled raised flower beds have a different runoff limit (.1 in) than my grass (.2) and my drip-irrigated lemon trees in pots are much lower (.05in.) AND, my county extension service (local government agricultural department) has average data for this they make available.
I was able to do some web searching for the plant/grass types I have to get the average water required in my part of the world.
Shawn – When purchasing drip systems, I believe the drip heads have a l/hr or gal/hr rating. The ones I have all have ratings from .5gal/hr to 2gal/hr (GPH) drip rates. I thought the same was true in the rest of the world for l/hr (LPH) but I suppose if you were using something hand-made or drip hoses that might be less visible.
I was thinking of how to build a solution for everybody (all users of OpenSprinkler) who don’t have PWS or solar panels. That’s the good side of using Wunderground because you can likely find a PWS near you. Is there a way to estimate solar radiation based on data available from most PWS?
I think you are right about Joules not being the right unit for solar radiation. You can convert from Joules to watt/m2 but watt/m2 is probably the right unit to start with. I got J from one of the python libraries I was looking at but it was petty academic and maybe not practical.
And I know exactly what you mean about building a solution on a unit you need to work – I have the same. It can be challenging. If it messes up I either end up with dead plants or a lake.
Luckily I use an OSPi which has far more computing capability than the Arduino version so I wasn’t worried about that but I appreciate why the Unified FW uses the cloud-based approach to offloading hard work from the Arduino.