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Help needed with Frequency Counter

Discussion in 'Electronics Homework Help' started by malsch, May 13, 2011.

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  1. malsch

    malsch

    4
    0
    Apr 29, 2011
    Hi, I need to design a simple frequency counter to measure the frequency of a square wave input (hence signal conditioning is not needed for now). I have understood the concept that the counter needs to count the input pulses for 1 second and display them on a 7-segment. My problem is how am i going to use the latch function (LE) to keep showing the frequency that was counted.

    This is what I came up with so far:
    [​IMG]

    The input signal (in this case 50Hz) triggers the 1Hz monostable, hence counts for 1 second. The problem is that after that 1 second, the counter resets to zero and recounts to 49 in this case. I need to find a way to keep the counter on 49 rather than going back to zero. Later I will add a 10Hz and 100Hz monostable for decimal points but for now I need to understand this concept.

    Thank you.
     
  2. Kabelsalat

    Kabelsalat

    132
    25
    Jul 5, 2011
    You should have a set of latches between the 74HC192 counters and the 74HC4511 decoders.

    Also using a 555 to get excactly one second is quite hard. For the counter to be correct you must be able to get a pulse that last for excactly one second.
     
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