What does this do?
This is an arduino sketch to track a gas meter with an ESP32 and QMC5883 sensor. The sensor is attached to the gas meter and will detect rotations of the counter and report them via Mqtt.
Requirements
- Gas meter with a magnet on one register/counter (eg. G4 RF1 style gas meters)
- ESP32 microcontroller
- QMC5883 chip (HMC5883 is also supported by the used library, you will need to adjust the sketch correspondingly)
- A mqtt server (if you want to use that - you can still edit the sketch to do something else with that information)
How does it work
Some gas meters have a magnet on the counter for the second decimal place. In my case it is nearby the “6”. If you now place a sensor on the top of the counter and the 6 passes by, you can detect the magnet with an increase in the magnet field strength (in case of a compass sensor) or by a contact closing (in case of a reed sensor).
This again means: Whenever you detect that magnet, the counter for the second decimal place did a full rotation - which again means that the first decimal place increased by one. Which in my cases indicates a gas consumption of 0.1m³ - or 1.0kWh.
Why not another sensor?
- I tried with a reed sensor in an aqara door- and window contact: it didn’t work out as it was not sensitive enough
- I was unsure which hall sensor to use
- I found this nice blog post on kompf.de and liked the idea to use a (quite sensitive) compass sensor
Setup
Rename Setup.h.orig to Setup.h and adjust the settings. The sketch will publish the MQTT debug event mqtt.0.gas_meter.debug - from this you can tell how to configure TRIGGER_HIGH and TRIGGER_LOW best. Be aware that in some situations the sensor will be measuring high values for hours (e.g. when the digit with the magnet is parked right under the sensor). From my experience TRIGGER_LOW should therefore be rather low, so that it is not in the range of the standard error of the sensor.
3D model for a holder
A matching holder for the sensor can be found here: https://www.thingiverse.com/thing:5581975
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