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  • i am an absolute beginner (and even worse with an enterprise programmer background) and thankful for every hint and critic :-)

    for my version of a word clock i am trying to use an e-paper display with an espruino pico

    the display is this one: http://smart-prototyping.com/NOA-Labs/E-­ink-E-paper-new-version-display-module-3­.3V-2.04-inch-177x72.html

    so far i have the components and i am on my way to migrate (luckily provided from manufacturer, some quite complicated command sequences) the arduino code to espruino

    the final goal is to run from battery, for this i would be thankful if someone can answer my questions

    my take on power consumption

    • assuming 2s operating time every 5 minutes (its a word clock, update every 5 minutes is enough for me), 24s per hour
    • Pico deep sleep needs 0,02mA/h
    • Pico operating needs 32mA/h
    • Display operating needs 8mA/h (but it is an e-paper, power is only needed to update the display, content stays after that)

    Pico current draw in mA/h = 0,23 mA/h = (0,02mA/h:3600s*(3600s-24s)) + (32mA/h:3600s*24s)
    Display current draw in mA/h = 0,053 mA/h = 8mA/h:3600s*24s
    final power consumption ~ 0,29 mA/h

    • assuming 1900mA/h from 2x AA eneloops (2.4v)
      • according to the specification the display works from 1.9v - 3.3v

    operating time ~ 0,76 years = (1900mA/H:0,286533333 mA/h:24h:365d)

    i know that is just a theoretical value, voltage drop will probably happen earlier

    Questions

    • Is my take on the power consumption correct?
    • Are 2.4v enough to drive the pico?
    • Is it possible to control the VBAT Pin to only activate at designated timer?
      • So far i think i need a transistor, but maybe it is possible without an extra component.
      • Are there alternatives to my approach? (can a GPIO pin drive the display? i am not sure about the current draw)

    updated

    • was 2s operating time per hour, but should be (60min/5min)*2s=24s
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