@jvdk I agree with the point made by @evb , why would you want to wire connect the ultrasonic node rather than the usual radio connection ? You are adding levels of complexity and power demands for what reason ?
My ultrasonic water tank node (pro-mini+rfm69) is now 2 years on the same 2xAA batteries sending in levels every hour (RTC), the only problem encountered - condensation forming a drip on the face of the ultrasonic head during very low temperatures.
following this thread loosely.
I have the following sensors and they seem to be accurate to some degree:
http://www.aliexpress.com/item/DFRobot-Capacitive-Analog-Soil-Moisture-Sensor-3-3-5-5V-Corrosion-Resistant-with-Gravity-3-Pin/32574020064.html?spm=2114.01010208.3.2.P99ddH&ws_ab_test=searchweb201556_0,searchweb201602_1_10037_10017_507_10033_10032_10040,searchweb201603_1&btsid=8d3b5e46-a069-441a-a1f7-491ae7e317e1
and they are much easier to work with Arduino compared to Watermark stuff. Anyone agree?
@tiana I have not used it, but it is possible to create different revisions. See https://www.openhardware.io/view/4/EasyNewbie-PCB-for-MySensors#tabs-revisions as an example.
@epierre said:
Both need protection (internal or external) from excessive discharge (or excessive charge, and short circuits etc)
That is where our new library to check battery level goes in, we could dream to have an internal mysensor security check of a LiPo battery ! they do so in 'copters
I may pass on that. I'm not used to software glitches having quite so much potential impact, and I don't need to save every gram. But to each their own!