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pulse count

Discussion in 'General Electronics Discussion' started by ADJ, Dec 22, 2010.

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  1. ADJ


    Dec 22, 2010
    I would like to install a flow meter on my agriculture aircraft. The meter sets in a 2 inch housing in line of my spray system. As liquid flows through the housing it rotates an impellor which produces one 5 volt pulse for every revolution. 720 revs equil one gallon. I've got the pulse count displayed on a 7 seg disp using a 555 timer and LED driver. Howerver I would like the circuit to display the reading in gallons (total pulses/720 = gallons). Any ideas?
  2. Laplace


    Apr 4, 2010
    This is the sort of project that begs for implementation with a microcontroller. The basic program would count impellor pulses in a register, reset the register when it reaches 720 and also increment the display register. It is a one-chip solution versus doing the same function in hardware. A hardware solution would use a 10-bit binary counter with gated sensing for the 720 pattern 1011010000 to reset the counter on the next impellor clock pulse. It could be an asynchronous ripple counter but the reset would need to be made synchronous with the input pulse. The reset pulse would also be the clock pulse for your existing counter.

    edit: You could eliminate the gated sensing by using a settable counter to start the count at a value of 1024 - 720 and using the falling edge of the 10th bit as the reset.
    Last edited: Dec 23, 2010
  3. ADJ


    Dec 22, 2010
    Hmmm. I have a Basic Stamp I've not even got outa the box yet. Not to familiar with microconstollers as of yet. I may have trouble with the programming, however, it will make the finished product more user friendly because I will be able to change pulse count per gallon. For example, the counts per gallon will change depending on the specific gravity of the spray solution. Some mixes I spray are thicker than others. The 720 count I came up with is a ballpark for most sprays.
    thanks for your thoughts

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