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Pullup or pulldown in battery-powered applications — Parallax Forums

Pullup or pulldown in battery-powered applications

Lord SteveLord Steve Posts: 206
edited 2009-12-30 01:18 in General Discussion
From a power-consumption view, is it better to pull normally-open pushbuttons high or low?

Comments

  • LeonLeon Posts: 7,620
    edited 2009-12-28 04:59
    What sort of inputs? With CMOS it doesn't make any difference.

    Leon

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  • Lord SteveLord Steve Posts: 206
    edited 2009-12-28 05:11
    User inputs into a Propeller via simple normally-open pushbutton.· Software can handle either case, pulled high or pulled low.

    If it doesn't matter which way it's pulled, for battery-powered applications is there a suitable resistor size?· In other words, I usually use 10K resistors, is that too little?
  • kwinnkwinn Posts: 8,697
    edited 2009-12-28 07:39
    10K is a pretty good choice. Low enough to reliably pull a cmos gate high or low without drawing enough current to have much effect on battery life when the buttons or switches are closed.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-12-28 10:33
    For the most minimal effect on battery life, connect the other end(s) of the pullup(s) to a pin which is driven high only when the switch(es) is/are being read. That way, for any switch being activated, current will be drawn only during the few microseconds required to poll it.

    -Phil
  • Lord SteveLord Steve Posts: 206
    edited 2009-12-30 01:18
    PhiPi said...
    For the most minimal effect on battery life, connect the other end(s) of the pullup(s) to a pin which is driven high only when the switch(es) is/are being read. That way, for any switch being activated, current will be drawn only during the few microseconds required to poll it.

    -Phil
    Good idea!
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