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variable voltage switch?

Discussion in 'Electronic Basics' started by John Doe, May 19, 2007.

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  1. John Doe

    John Doe Guest

    Using an 18 V cordless circular saw, but for a different purpose than
    intended. Apparently the switch is either all or nothing (makes sense
    IMO to help avoid binding during a cut).

    If variable speed DC motor requires a large heatsink, how about just
    four different speeds using simple switches? Someone in the design
    group answered this question with a drawing but I cannot locate it in
    the archives.

    I figure that's easy just by putting batteries in series and then dial
    switching in between the batteries. But that would wear the batteries
    unevenly. Could anyone please illustrate a four position switch that
    would provide zero plus three positive voltages, maybe switching the
    batteries to parallel so that current drain is even on all batteries?

    Thank you.
  2. John Doe

    John Doe Guest

    I found how to easily do that with just two positive voltages.

    Is there a reasonable way to provide more than two positive voltages at
    the same time providing equal battery wear?

    -------+-------/ O-------+-------------- To motor
    ! ! !
    --- ! ---
    ! + ! ! ! + !
    ! ! ! ! !
    ! - ! ! ! - !
    --- ! ---
    ! ! !
    ! ! / ! /
    ! -------/ O-------+-----/ O---- GND
  3. Charles

    Charles Guest
  4. John Doe

    John Doe Guest

  5. Jasen

    Jasen Guest

    a buck/boost DC-DC converter

    or if it's just to run a motor pulse-width modulation. (PWM)

  6. Chris

    Chris Guest

  7. Jasen

    Jasen Guest

    what's high? 10A 100A 1000A ?

    what is your control signal source?

  8. Guest

    Google electric scooter parts. Plenty of cheap hi amperage (sorry,
    current - why is it OK to say voltage, but considered gauche to say
    amperage?) controllers of all varieties. jack
  9. Jasen

    Jasen Guest


    current - 2 syllables
    voltage - 2 syllables

    amperage - 3 syllables

    electromotive force - 6 syllables
    potential - 3 syllables

  10. Guest

    Good thought. The cause of much popular usage.

    But Horowitz and Hill (Art of Electronics) claims that the use of
    amperage and ohmage is in the realm of the bush mechanic.
    I wonder if there might be an element of professional snobbishness
    there. jack
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