Photogate timer question help, please.

Discussion in 'Homework Help' started by dfb23, Feb 18, 2010.

  1. dfb23

    Thread Starter New Member

    Feb 18, 2010
    3
    0
    I'm probably looking into it too much. Here's the question:

    Consider a case where light is briefly blocked and subsequently briefly blocked again. What circuitry might be added to our photogate timer so the time from the start of the first block to the start of the second block can be measured? Assume the photogate out put is high when the light is blocked. Add a CLEAR* signal (to a pulser on the digi-designer) which sets up the circuit before the block.

    Then figure out a way to measure the time from the end of the first block to the end of the second block.

    Then using the results from the first 2 (posted above) figure out a way to measure time from the end of the first block to the beginning of the second block.


    Thanks in advance guys.
     
  2. dfb23

    Thread Starter New Member

    Feb 18, 2010
    3
    0
    I should add:

    I don't understand how to measure the L period of the photogate timer. I ran the phototransistor (photogate and schmidt trigger) through an AND gate, lets say thats input B. Input A is the signal generator and freq. meter. The output of the AND gate gets connected two three 74193 IC counters. The 74193 get connected to a 3 digit Hex Display and each other.

    If the signal of the phototransistor is H when no light is present, it would stop counting after the first block and before the second block. I'm confused as to how I would make it count that interval, as well as the others posted. I think for the last one to measure the time from the end of the first block to the beginning of the second block I can put an INVERTER at the end of the Schmidt Trigger. As for one and two I seem to be at a loss, possibly a EXCL-OR gate for number two.
     
  3. dfb23

    Thread Starter New Member

    Feb 18, 2010
    3
    0
    EXCL-OR wouldn't work, I think i'd need an OR
     
Loading...