I’ve been playing a little with the fantastic open source home monitoring and automation solution openHAB on a Raspberry PI 2 . Having started off with some small temperature/humidity sensors I was looking for something else to add and the stats from the Solar panels were an obvious want.

I previously had the Inverter monitored using using Auroramon as described here. This was great but it’s stopped working and I’m putting off crawling around the attic to debug the issue for as long as possible.

I can keep an eye on the Inverter output using a standalone wireless monitor, the OWL Micro+, which has a small transmitter sensor clamped to the output from the Inverter giving current generation statistics. There is however no way of hooking this up to a computer to record the stats, so enter rtl_433..

The rtl_433 application uses an RTL SDR dongle to receive and decode a huge selection of wireless sensors transmitting on 433 MHz. I didn’t see the OWL device in the list but on running rtl_433 we see statistics generated every 15 seconds when power is being generated and totals every 60 seconds when there’s no generation.

Energy Sensor CM180 Id 62a0 power: 48W, total: 11242215648W, Total Energy: 3122.837kWh

With the output from this we can pull out the power generated and send it via an MQTT message using mosquitto_pub to a listening MQTT broker we have openHAB set up to use already.

This is ghastly but it works for now, for some reason the unit reads 48w when idle so there’s a bit of fiddling to make it idle at 1:

rtl_433 2> /dev/null | xargs -I {} sh -c “mosquitto_pub -h 192.168.1.1 -t solar -m \$(echo {} |  sed -e ‘s/, .*//’ -e ‘s/^.*: \([0-9]\+\).*/\1/’|while read spo; do if [ \$spo -gt 50 ]; then echo \$spo; else echo 1; fi; done)”

I’ve made some changes to my set-up where everything is now being fed in to node-red which processes MQTT messages so the following is a bit more simple and outputs in JSON and lets node-red do the filtering:

rtl_433 -R 12 -F json 2> /dev/null | parallel –tty -k mosquitto_pub -h 192.168.1.1 -t solarout -m {}

At the openHAB side I’ve an item “solar” set up and can see the current generation and day/week charts, it’s been running a few days now and been no problem at all!

Future plans with this one will be to capture the output in a less Frankenstein manner or maybe risk broken ribs by crawling around the roof space to fix the monitor on the Inverter.