It is sometimes fun to think of a cool problem and come up with an electronic solution. Have a look at this project that Matt Meerian from Home Brew Electronics put together, it is a way to Shoot a Bullet through a Spinning Propeller Blade. This was a common problem years ago when planes needed to have a forward mounted gun shoot through a center propeller. Matt thought it would be a cool challenge to complete with a microcontroller and a handful of electronics. If you are wanting to give this project a try Matt has the project code in his writeup.
“The software isn’t too complicated. When the user presses a button, the analog comparator interrupt counts the time (using Timer 1) between the propeller blades passing the infrared sensor mounted under the gun. Once we know how fast the propeller is going, the software then looks for analog comparator interrupt and counts 1.5 times the time between the blades, minus the time it takes the pellet to come out of the gun.“
