Pullup or pulldown in battery-powered applications

Comments

• Leon Posts: 7,620

  2009-12-28 04:59 edited 2009-12-28 04:59

  What sort of inputs? With CMOS it doesn't make any difference.
  
  Leon
  
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• Lord Steve Posts: 206

  2009-12-28 05:11 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?
• kwinn Posts: 8,697

  2009-12-28 07:39 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) Posts: 23,514

  2009-12-28 10:33 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 Steve Posts: 206

  2009-12-30 01:18 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!