Digitise an older engine - ESP32

[PaddyB]

I know I responded on the video, but it works great, we see a 9v pulse I think out of the alternator and it's as accurate as the VP gauge so I'm really pleased with that. The other plus for me was that both work at the same time and I didn't have to try and stick magnets to a spinning part of the engine. - Thanks again

Ta, can't remember where I copied the design from but glad it works  

Hoping RPM in signalk will give a little hint of how clean the hull/prop is - do you save everything to influxdb? 
Plotting data is pure gold dust at seeing hidden patterns invisible if just looking at some numbers.