*Newb* Help finding continuous Frequency counter

Discussion in 'The Projects Forum' started by Rich2287, Dec 2, 2009.

  1. Rich2287

    Thread Starter New Member

    Dec 2, 2009
    hi im building a BPM counter for uni and i was wondering if anyone knew of a continous frequency counter as opposed to a stop and hold design that i can buy as a component, thanks
  2. SgtWookie


    Jul 17, 2007
    Hello Rich2287,
    Welcome to AAC (All About Circuits). We're a pretty casual bunch here, but using abbreviations without definitions can cause some confusion.

    For example, what do you mean by BPM? Is that Beats per Minute, as in heartbeat?

    (I take Uni to mean "university")

    Did you have a particular range of frequencies in mind for input?

    What is the voltage range for input?

    Did you have an output data rate/update rate in mind?

    Will the output be to an LCD, 7-segment LED, or some sort of computer interface, or perhaps a printout?

    What is the required accuracy percentage? (this will affect output data rate/update rate).

    What type of voltage supply do you need this to operate from?

    If battery powered, how long does it need to operate?

    This isn't the end of questions that may arise; only some basic specifications that need some qualifications.
  3. Wendy


    Mar 24, 2008
    All counters take continuous samples, it is how they work. If you go with period instead of frequency the gating is rearranged, but it is still a sample. Sample and hold is not the norm, at least in the sense that you take one sample and stop.

    Buffering for the display is pretty much required, trying to watch a fast counter count is gibberish.

    Period measurement (which can be converted to frequency with modern CPUs easily) is faster for low frequencies since only one cycle is required to capture the number. I suspect this is what you want. It tends to be slightly less accurate since a sample of one (vs a count of many cycles) can vary more.
    Last edited: Dec 3, 2009
  4. Rich2287

    Thread Starter New Member

    Dec 2, 2009
    Hi, sorry that was a very brief description, im completly new to circuit design so alot of this might not make sense. however, im designing a beats per minute counter in relation to tempo.

    the input is roughly 512 hz (120 BPM) i want to use a comparator with a reference signal of 50khz and then find a way of displaying this on an 3 digit display.
    ive heard that there is a (device/component/IC) that uses a comparator along with a quartz crystal that can convert the frequency so that it can be displayed all in one unit instead of me having to build all the circuits. my original idea was a 555 timer and a comparator circuit but after the comparator circuit im a bit lost as to what to do next
    accuracy needs to be at least 0.05hz ( i think)

    I was planning on powering the unit with two 9v batteries. the output needs to be converted into BPM from frequency.

    thanks in advance