Hello there,
The breakout sensor is not required for any connections…it just makes it easier to make the connection, as you get a RJ-45 connector at the bottom of your EZFlora, so you’d have to splice open a Cat5 cable and know which wires are going where to make the correct connection.
A water meter is not required to use the rain sensor either. The breakout connection manual is simply letting you know how to connect a compatible meter, not saying that you have to connect a water meter to use the rain sensor.
Any rain sensor that is a normally closed dry contact and opens when rain is sensed would work with the specified resistor.
I hope that helps!
