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A rectifier that counts?

Discussion in 'Electronic Basics' started by Randy Gross, Dec 1, 2003.

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  1. Randy Gross

    Randy Gross Guest

    I have looked at quite a few circuits in the last few days: voltage
    comparators, frequency to voltage converters, voltage regulators, frequency
    counters and magnetic pickups when a thought crossed my mind.

    Has anyone used or, know of a circuit that uses the rectifier as a
    frequency source instead of a magnetic pickup. Each time the rectifier
    conducts positive (or negative for this matter), this is counted for the
    time period, converted, and fed to a comparator. Whatever decision is made
    is then passed on to the motor speed controller.

    I haven't run across one like this, yet. The 3 latter circuits are no
    problem. It's the frequency sensing circuit I'm after.

    Inquiring Mind
    Randy
     
  2. Why not use the AC upstream of the rectifier as the frequency source?
    That can be squared up and fed directly to the frequency to voltage
    converter, or to the phase detector in a phase locked loop.
     
  3. Tim Shoppa

    Tim Shoppa Guest

    I don't think you want to use the diode as a "counter" in itself,
    I think you want to use it as a pickup. In which case a photodiode
    certainly counts :)

    (I originally had a response where I put "diode" and "counts" together
    to make a divider, like the old regenerative frequency dividers that were
    common in the 50's and 60's, but I don't think you intended to ask about
    that subject.)

    Diodes are exceedingly common for "counters" of radiation from visible
    light on up in frequency. Put a scintillator in front of one and you
    can detect non-photons, too. Here I'm using the word "counter" in the
    nuclear physics sense, not the electronics sense. Nuclear physicists call
    electronic pulse counters "scalers", not "counters" :)

    Magnetic pickups have been much more common in typical automotive/
    industrial environments than photodiodes because they are nearly
    impervious to dirt, grease, grime, and stray light. OTOH inductive
    pickups are potentially more sensitive to medium and large-scale EMI,
    and in many areas they've been replaced by solid-state Hall detectors
    in the past few decades.

    Tim.
     
  4. N. Thornton

    N. Thornton Guest


    Hi Randy. I've seen the transformed 50 or 60Hz used as a clock signal
    before, its a minimal cost way to get a pretty steady lf clock.
    Mechanical synchronous clocks locked onto mains frequency for decades,
    with fairly good results, several are still in use.

    Also the ac waveform is fed to a comparator in pseudorandom
    generators.


    Regards, NT
     
  5. Randy Gross

    Randy Gross Guest

    <>...
    : Randy Gross wrote:

    <Snip>

    : It's the frequency sensing circuit I'm after.


    Couldn't see the forest for the trees;-)

    Randy
    :
    : Why not use the AC upstream of the rectifier as the frequency source?
    : That can be squared up and fed directly to the frequency to voltage
    : converter, or to the phase detector in a phase locked loop.
    :
    : --
    : John Popelish
    :
     
  6. Genome

    Genome Guest

    Err, perhaps you are thinking of a motor controller driven by some
    thyristors or SCRs or other such wildebeasts. Don't know how you arrange the
    thingies but you do and then you fire them off from some zero crossing
    detector counter other thingy such that, if it were so many bits then it
    would go....

    On,On,On,On,Off,Off,Off,Off

    or

    On,On,Off,Off,Off,Off,Off,Off

    and all perambulations and combobulations thereoff (or thereon) to achieve
    speed control of the motor.

    Make sense?

    Of Course

    AND
     
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