Detecting rain


These are notes on on ongoing "project" that i sporadically work on, not actual documentation of how to achieve anything.

Hydreon RG-9

NameHydreon RG-9
ESPHome componenthydreon_rgxx
RS232 Protocolrg-9_protocol.pdf
Input voltage

Uses IR light sensors to detect rain falling on its curved plastic lens, and can detect rain very fast. The sensor communicates over a serial UART connection, and pulls a pin HIGH when rain is detected.

The specific model that I am using (RG-9) is designed for "is it raining now?" use cases.

The Hydreon RG-9 Solid State Rain Sensor is a rainfall sensing device intended to detect and communicate when a pre-selected rain intensity has been reached or exceeded. The RG-9 is rugged, reliable, and maintenance-free.

The RG-9 uses beams of infrared light within a plastic lens about the size of a tennis ball. The round surface of the lens discourages collection of debris, and the RG-9 has no moving parts to stick, and no water-pathways to clog.1

It's faster at detecting current rain than a "tipping-bucket" style sensor, more local and accurate than weather APIs. Combining local sensors and weather APIs may be useful.


RG-9 pinout

Z-Wave tipping bucket: POPE700168

A tipping bucket-style Z-wave rain sensor.

Weather APIs

Using weather APIs.


Home Assistant forum thread: Hydreon RG-15 rain sensor


Home Assistant forum thread, posts from janick