I am trying to make a simple circuit to mark/count revolutions of my dad's hit and miss engine. He's trying to figure out how many revolutions it makes in a day (8 hours). I did figure out how to make a "counter" but now I'm really stuck on how to "count" the revolutions. Hit and miss engines don't really have a constant speed so the magneto is unreliable. So, in my mind, I am thinking of painting a white mark on the rusty wheel. This is to give contrast for a photoelectric circuit. The rusty area will be "off" or zero and the white mark will be seen as an output a "on" or one and be logged with a counter in a separate circuit.
Should I use a phototransistor or a photodiode? I ask this because I know that it will be dusty and dirty (from the environment) so I would like to make something kind of durable. And it will probably get a little wet too.
I thought about sticking a magnet to it and using that to mark/count it, but the flywheel isn't "perfectly" round. This is the reason I was thinking about a photoelectric circuit. I know this probably seems like child's play to you but I'm looking for suggestions. I do I have an understanding of basic electronics. My problem is when I google this kind of question it talks about high tech photoelectric circuits loaded with technical stuff that I'll never understand and way out of my price range. I'm trying to keep this as simple and durable as possible.
If you have any suggestions, please email me at the above address or here. I'd love to hear your thoughts.
Todd