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Originally Posted by BillyJ
We want to make a sensor that can measure our shooting wheel speed. Reading threads it seems like there was a "Banner" sensor that could measure white tape on a wheel, but I haven't been able to find that at digi-key.
One of my friends told me about this, would this work?
http://rocky.digikey.com/WebLib/Opte...OPB715,716.pdf
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It might, but you can only calculate the theoretical speed. You can also try the gear tooth sensor.
You might be able to use a decent powered led and a phototransistor. The ball will pass in between them and cut the light to the phototransistor. Set the interrupts to fire on the falling edge(when it reads 0). Then recored the time at that point of a timer and set the pin to fire on high next and when it fires again on high record the time again. The ball is usually a constant 7 inches, so using that and the time you can calculate the velocity. Go to radioshack and ask them.
It is more complicated but I think it will be much more accurate.
Sorry, I haven't tired it, so I can't prove it.