This project enables me to read the gas meter using an optical sensor, the TCRT5000. The last digit of the meter has a reflective '6' that triggers the optical circuit. The board is powered by the well known HLK-PM01, and uses an arduino pro mini (clone). The nrf24 is fitted into a board that provides a proper 3.3v voltage. The board can receive OTA firmware upgrades
The sketch (that i adapted from Sandor Incze & Michel Schilthuizen) uses debounce, and raises the counter only if filtered pin value goes from 0 to 1. There is no problem if the meter stops at the '6'. If the sketch starts, it asks the controller for the last known value.
I use domoticz to present the readings. At this moment, there seems to be a problem with the large numbers that my meter uses, I still need to figure this out.
Future updates consist of using a fuse and thermistor with the power supply to make it more safe, and to create a nice casing.