Quote:
Originally Posted by TheOtherGuy
Not very exact (off the top of my head, I'm pretty sure it's right) but it is much more accurate than it sounds. We'll map this out and create some relationship between the motor speed and distance. We're planning on using the height or size of the target as the distance calculator. If we have time we'll add some form of revolution counter to the shooter for more a more determinate angular speed than PWM values (3500rpm is kinda fast for an encoder... I saw 111 used a reflection sensor on their 2006 robot in the "Behind the Design" book? perhaps that'll work...).
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A good way to sense speed on a high velocity wheel like that would be to put a small magnet into the wheel (drill a small hole and put an iron nail in, slice the head off), and set up a hall effects sensor. Each rotation should be VERY noticeable, so you should be able to get some speeds out of that....