Thanks very much! I ordered the sensor and I will print your design Elster watermeter reader by roumen - Thingiverse
This was my initial design, I now use a proper 12V to 5V DC-DC converter as the LM1117 tends to run a bit hot and could become unreliable. I use this one: https://nl.aliexpress.com/item/1005005505236083.html
Kind regards, Roger.
@joe2 - Can you share what your hardware is at the pool pump end. What physical sensor are you using to read the GPM ?