I built my own opensprinker by myself and change it to my old sprinklercontroller made by german manufacturer Gardena. Gardena is a well known brand in Germany and Europe and Gardena sensors are often in use with Gardena controllers. Unfortunately Gardena sensors has different output then others. My reverse-engineering shows the following. Gardena works with three output-conditions to detect if sensor is present and dry or wet:
endless = no sensor present, 10kohms = sensor present and dry, short = sensor present and wet
Therefore a direct connection Gardena sensor to OpenSprinkler isn’t possible.
My “quick&dirty” solution is a simple relais between sensor and controller. Cause I don’t want to overload the 5VDC from controller by tests, I use 24VAC from AC-Poweradaptor. A diode and a 78L05 make 5VDC from 24VAC. Relais is a 5VDC-type and in line with Gardena-sensor to ground. Relais switches a LED to control (not really neccessary) and with the other switch sensor-input from OpenSprinkler. It’s not very nice and built in 10 minutes only for testing purpose, but it works fine for month.
It should be for Gardena rainsensor 1189 and soil moisture sensor 1188.
So at the weekend I have a little time for my OS and I have had change my “Quick&Dirty” solution to a much better solution.
Its much simpler, to convert Gardena-sensors: connect Gardena-Sensor to OpenSprinklers sensor connector directly and make a 4k7-PullUp from the left pin (go to Atmega) to +5VDC (Pin 1 of External Connector). Thats all, its all done!
To indicate, if rain ist alert, it’s possible to switch a LED between left pin from sensor-connector to +5VDC (catode on sensor pin, anode over about 500 Ohm to 5VDC).
Maybe it helps others, to connect the european Sensors easy to OpenSprinkler 😉