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anybody make variable duty cycle Hall Effect switches?

Discussion in 'General Electronics' started by Scott Carter, Jan 11, 2005.

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  1. Scott Carter

    Scott Carter Guest

    Greetings guys and gals -

    Several manufacturers (at least Infineon, Allegro, Melixis, Anachip;
    probably several others) make low power duty cycled Hall Effect switches.
    The low power flavor appears to be typically about 0.1% duty cycle, with
    a sleep interval in the 50-200 ms range.

    Does anybody know of a manufacturer of a similar part where the duty cycle
    mode can be either externally adjusted (ideally), or at least turned on
    and off by a pin?

    I have an application where most of the time the low duty cycle is exactly
    what I need for its low power consumption, but there are times (known to
    the code) when the rotating element is rotating fast enough that the low
    duty cycle misses some rotation pulses.

    The obvious solution (and the one I expect to have to implement) is to use
    two switches next to each other, one the low duty cycle variety, and the
    other a high duty cycle which would usually be powered down. But the
    geometry of where the sensor wants to be makes fitting two, even SOT23s,
    suprisingly difficult. If some obscure manufacturer known to the
    remarkably knowledgeable denizens of this group makes the similar thing in
    e.g. a SOT23-5 with a control pin I'll be very happy (and buy a few hundred
    thousand of them).

    Thanks in advance for any help -

    Scott
     
  2. Robert Baer

    Robert Baer Guest

    Why not use a *linear* hall detector andd add your *own* logic to it?
    Allegro has them.
     
  3. Scott Carter

    Scott Carter Guest

    Fear of the unknown aka laziness :}, BOM cost, power consumption of the
    discrete implementation, fear of not getting the chopper stabilization
    quite right...

    But a valid point nonetheless.

    Scott
     
  4. Robert Baer

    Robert Baer Guest

    Power consumption is adjustable via programming on/off duty cycles.
    The Hall effect transducer would eat the most power (when on).
    Everything else can be low power logic and op-amps and presumably left
    on.
    With a 5V supply, CMOS has almos zero drain at low frequencies, and
    there are a raft of opamps that have rather low power requirements.
    Chopper stabilized? What the heck for?
    However, if you insist on using something you do not need for the
    implimentation, there are a goodly number of off the shelf chopper
    stabilized opamps - and some may have reasonably low power requirements.
     
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