An old homework assignment

Discussion in 'Homework Help' started by Moosatious, Nov 19, 2010.

  1. Moosatious

    Thread Starter New Member

    Nov 19, 2010
    There was a homework posting over a year ago, where the assignment was to first have a reversible motor go forward for 10 seconds, stop another 10, then reverse another 10 seconds-- something like that. The original post is too old to respond to, but I feel compelled to respond, in a manner of speaking, because even though he got the thing to work, he committed an all to common error: he didn't "design" his system. Instead he just threw parts at the problem. The correct thing to have done would have been to clearly (with at least a few English words) define each STATE of the system. Then, draw a state diagram, with a circle representing each state, and an arc representing each transition. The fact that timers were needed complicated things a little bit, but not that much. By using more than one 555 chip he could have made the design easier, but the cost higher. It should have been possible to do it with one timer.
    A more sophisticated design would have used a clock and counters. But the same state/transition diagram should have applied in either case.

    PS: Anyone know where I could actually get PAID to do this stuff anymore? LOL. Hey folks, I remember the days of DTL RTL logic, which was used because TTL chips were about $20 a pop. Can you imagine that? Don't laugh, Burroughs mainframe computers were still using CTL logic as late as 1979.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    We bought TTL floor sweepings at Mike Quinn's (Oakland) for $4.00 in case two or three gates might still work.