[Matt Krass]

Originally Posted by schenkin

Hello all. I am trying to figure out a way to measure rpms, eventually this will lead to an approximate muzzle velocity of our ball shooter.

So far, I've come up with a couple of possible sollutions:

1. Use a seperate controller (probably our edubot), to count up encoder interupts, poll this data at a set interval from the main controller (probably over a few digital in/outs), and from this get rotations/time. The main problem with this is that I haven't gotten the encoder code to run properly on the edubot. If someone could help with this, i'll post the problems i'm having.

2. Use an analog device which outputs speed as variable voltage. So far i've been playing with just using a standard DC motor to generate a current, and feeding that back into the controller, but I have no idea what the sensed voltage range is in the A/D controllers, and I very much doubt that the output is going to be even close to linear. Is there an actuall sensor that will do this for me?

Any help would be appreciated! So far this forum has served me well!

We tried both, ended up with #2 for simplicity, its not perfectly linear but its pretty close, it worked out well for us