OpenSprinkler Forums OpenSprinkler Unified Firmware Penmen-Monteith ETo method python script for possible use as weather script Reply To: Penmen-Monteith ETo method python script for possible use as weather script



The actual water needed is delivered by the script provided in the first post, the ET value. As far as runoff (saturation point) values there is quite a few different calculations and after researching for quite a while I found that 15mm per hour is a good starting point for most soils. If you have sandy soil this will go up, and hard clay soils or steep grades it will go down.

Historical data, watering logs, and a running ET balance are crucial to maintaining a watering plan.

scottsh-Drip systems have been giving me headaches for months, all my personal watering equipment can be accessed above ground and I can run my dripline into a cup and get the rate at which it “precipitates” and doing a bit of rough math came up with a “mm/sec” that works for me. My ultimate desire is to have this calculated scientifically and properly.
As far as solar radiation is concerned most water sense approved devices use a calculation to adjust readings taken from a semi-local weather station. I simply used the external radiation and cloud cover percentages (calculated based on charge rate from the solar panel, not a true solar radiation measurement) from my PWS. After purchasing a solar radiation sensor and running the numbers side by side for just under 2 months, I was within 10% of measured. Seeing as the solar radiation plays the smallest part in the calculation for ET I accepted the error rate as fair.

I am currently working out how to write all of the nvm data to the SD card on the avr based OS, so that I could have programs that do not require encoding of the times as this skews watering times quite heavily. It appears as though StdioStream in the SDFat library gives me the few basic functions required to mimic the OSPi and BBB versions using the “nvm.dat” file. I have to write/copy the nvm read and write functions for the avrOS make a few changes to the weather.cpp file and I should be able to get everything working.

Takes a while because I need my controller to work while I experiment on it…I should probably shell out the extra cash for a bench/test unit but it’ll probably be winter by the time I don’t have something else for my money to go to, cars and computers are expensive hobbies.

scottsh-where in the world do they use Jules for weather related solar radiation calculations? I have always used Watts/M^2, going between the US and Germany quite a bit I thought I had the metric and imperial systems down, but it looks as though I’ve missed a measurement.