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bike light riddle

Discussion in 'Misc Electronics' started by [email protected], Jul 28, 2013.

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  1. Guest

    I have a bicycle light, Opticube, standard unit,
    single button, uses 2 AA batteries.

    1. Push button, light on.
    2. Push again, hold 2 seconds, off.

    1. Push button, light on.
    2. Push again, blinking mode.
    3. Push again, hold 2 seconds, off.

    But when the batteries are low, the
    'hold, then off' time lengthens to 5 seconds.

    What's the timing circuit?
  2. Jasen Betts

    Jasen Betts Guest

    pronbably a 4 bit microcontroller.
  3. I thought he was asking about why he had to hold the button down longer
    when the batteries are getting weak.

  4. Guest

    Could be.
    But I thought a microprocessor, with its support
    components, would be overkill, too costly, for a
    cheap consumer item. Especially with such simple function.

  5. Jasen Betts

    Jasen Betts Guest

    there's plenty of microcontrollers that'll run on anything between 1.8
    and 3.3V and need no external parts, eg: ATTINY4-TSHR or
    PIC10LF320-I/OT under a buck in small quantities, much cheaper in lots
    of 100000 as bare dice for chip-on-board construction.
    "what's the timing circuit"

    It's a microcontroller, the clock is probably the on-chip RC clock,
    it's slower to turn off possibly because the designer intends that
    behaviour as a warning that the batteries are low. it's better (and
    easier) to warn of low batteries at turn-off
  6. Guest

    Deliberately? Possible, but seems odd.

    These chips require no external oscillator?
    How does it know the battery is low?

    It will drive a FET switch (for the bulb) without
    a buffer? What are the minimum necessary external
  7. Chances are good that it may be some dedicated IC in there. If someone an
    cook up enough demand, it's simpler for a dedicated IC than everyone
    working on their own.

    I have some single LED "bicycle lights" that are smaller than a 9v battery
    and you attach to the handlebars with the included elastic. They cost
    $3.75 Canadian. The first one I bought, it had slow flash, fast flash and
    steady on, you'd press the button and advance the mode, then another press
    ona off. The mroe recent ones do away with one of the flash modes, so
    it's only continuously on or flashing. At that price, you can't spend
    much time adding parts to a circuit board, so chances are good it's
    dedicated to it. For all I know, it may be what's used in the bigger LED
    bike lights, which of course have a similar ability to flash and stay on,
    and use the on/off button for the same function.

    So if it's a dedicated IC, chances are good as much as possible goes in
    the actual IC (which would just be an expoxy blob).

  8. The controller clock might be driven from the switching power supply
    signal, either intentionally or not.
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