Counter Help

[photosam]

Hello, thanks in advance for the help!
I 'm trying to execute a simple idea with crude tools and am seeking help with the project.
Essentially I have a wheel rotating inside a photogate interrupting the beam with spokes. I would like to latch an alarm if it rotates too fast in a certain amount of time. I am trying to use a 74HC163 counter for counting the number of times that a pulley rotates, a 955 timer for the clock, a 5.5V power supply and a nand gate to latch and clear to do this. However for some reason I am not able to get this setup to work. Advice?

Thanks!

 

[Laplace]

I would try using the counter to accumulate time between spokes. Use the spoke detection to reset the counter. If there is a carry-out before the next spoke then the wheel is rotating slowly. But if the spoke is detected before counter overflow then the rotational speed is too high.

Or you could avoid the counter and use a monostable timer to set the time limit between spokes. Use the spoke detection to trigger the monostable.