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What is the "sign of life"?

Discussion in 'Electronic Design' started by Boki, Jun 14, 2006.

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  1. Boki

    Boki Guest

    Hi All,

    I see a requirment of document, there is a LED to indicate the sign of

    What is that?

    This is to indicate device is still alive/active and not unresponsive?

    or it is a battery indication?

    Best regards,
  2. Probably "heartbeat". It's an indicator that blinks or clacks or
    whatever to indicate that the processor is still operating.

    Best regards,
    Spehro Pefhany
  3. Paul Burke

    Paul Burke Guest

    Are you designing another Mars rover? I'd suggest a large button on the
    outside, marked "DO NOT PRESS THIS BUTTON". If there are any Martians,
    they will inevitably press it, and you can light the LED.

    But I think Spehro probably has the right end of the stick.

    Paul Burke
  4. Deefoo

    Deefoo Guest

    Make sure to blink it from the main loop and not from a timer isr or
    something so that you are sure your main code is still executing.

  5. Boki

    Boki Guest

    Paul Burke 寫�:
    Ya, hurry up to press what you have designed by yourself...


    It is not so infrequent that embedded system has a HW reset button...

  6. Boki

    Boki Guest

    Deefoo 寫�:
    Thanks, but nobody think it maybe a battery indication?

    Best regards,
  7. Joel Kolstad

    Joel Kolstad Guest

    If it is, you can use a blinking LED to indicate as much (e.g., certain
    blink rates indicate the state of battery charge or multiple blinks in a row
    tell you something or whatever); this provides significantly more objective
    information than just running an LED off a resistor connected to your mian
    battery and asking people to correlate brightness to battery charge. (Such
    an approach is really almost useless -- if you use, e.g., NiCad batteries,
    the discharge knee is so sharp that the LED would go from full brightness to
    nothing usually over the span of some minutes).
  8. Pooh Bear

    Pooh Bear Guest

    Definitely not.

    If you wanted to be cute and the micro has an onboard dac, you could monitor the
    battery voltage and flash a bi-colour led green when the battery is good and red
    when the battery voltage is low.

  9. Or (cheaper) change the duty cycle or frequency of a single LED
    depending on battery condition. I'm not sure where the DAC would come
    in. Some micros have a comparator and absolute reference so you
    wouldn't necessarily even need an ADC for go/no-go indication.

    Best regards,
    Spehro Pefhany
  10. Pooh Bear

    Pooh Bear Guest

    Ooops. Typo. I did mean ADC but a comparator and reference would be fine too. Mind
    you, with the ADC you could change the led from green to red via yellow too if you
    liked !

  11. Guest

    You can do that with a ref and comparator too, just by adding a little
    ac or noise onto the reference line. Micros always have sources of that

  12. Pooh Bear

    Pooh Bear Guest

    Yes that would work too. What a source of bright ideas we are ! Boki, we expect this
    feature on your next product !

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