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Push button power usage — Parallax Forums

Push button power usage

FrannyFranny Posts: 127
edited 2013-09-08 09:17 in Propeller 1
Does it make any difference when push button pins are defaulted to high or low (pull up or down resistance) Does it take more power to keep the pin high or low?

Comments

  • T ChapT Chap Posts: 4,223
    edited 2013-09-08 09:08
    My guess is the same, the current used in pullup or pulldown is based on the value of the resistor. A 200 ohm pullup will draw a lot more than a 100k pullup.
  • Mike GreenMike Green Posts: 23,101
    edited 2013-09-08 09:17
    No, it doesn't take more power to keep the pin high or low. It's often easier to find a ground wire near the switch than to find a source of +5V or +3.3V to connect the switch to. Most of the time, the resistor is located near the microcontroller, so it's easy to find a source of +5V or +3.3V nearby or ground for that matter. Most of the time, there'll be a pullup resistor and the switch grounds that for the reasons mentioned. As T Chap mentioned, the current depends on the resistor and only matters when the switch is closed. You generally want enough current through the switch (and any connecting wires) to keep the switch contacts clean, to minimize RC charge / discharge times, and to reduce noise. 4.7K to 10K is a typical value with higher values (maybe 100K) where low power is important.
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