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Re: "fuel gauge"

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  • Bob Small
    I have found a way of using an LM311N as a voltage comparator to drive a piezo buzzer. The idea is that as soon as the battery voltage drops to to a certain
    Message 1 of 7 , May 1, 2008
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      I have found a way of using an LM311N as a voltage comparator to drive
      a piezo buzzer.

      The idea is that as soon as the battery voltage drops to to a certain
      voltage the buzzer will sound.

      The main problem is that the voltage curve of the typical Li-on and
      NiMH batteries is fairly flat, and then takes a fairly steep curve
      towards the end. So it would need a bit of experimentation to find the
      best "trigger voltage" that still leaves enough capacity to get you
      home, but doesn't trigger so soon that you don't get the most out of
      the battery.

      Take a look at http://www.electronics-
      lab.com/projects/models/004/index.html
      and us.sanyo.com/batteries/pdfs/lion_E.pdf
    • Bill Hart
      Here is another possible alternative. I drive a relay with small back- up batteries using the DCC output from the rcvr. To explain further - I did several
      Message 2 of 7 , May 1, 2008
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        Here is another possible alternative. I drive a relay with small
        back-
        up batteries using the DCC output from the rcvr. To explain further -
        I did several tests with Alkaline, Ni-Cad, NiMH, and Li-Ion. As you
        stated, with anything but the Li-Ion the battery dimishes quite
        rapidly
        at the end but there are clues the battery is getting low and I have
        always been able to get home.
        What forced the back-up battery idea was because the Li-Ion reaches
        the
        low power cut-off and it suddenly dies. But, because no power is
        being
        drawn from the battery the voltage will rise enough to cause the
        consist to suddenly start up, then immediately die again.

        To solve it I put a relay from a set of AA batteries to power the
        consist long enought to get home. AA batteries are not suitable to
        run
        the consist (Dash-9 and 25 cars) but it will allow me to limp home,
        although very slowly because the battery voltage drops a bunch with a
        large load. The back-up batteries have the extra advantage of
        allowing
        the locomotive to move my itself without an external power source.

        I function the relay with F12 so I won't accidently punch it without
        paying attendtion.

        Bill
      • Bruce K. Bates
        Just a note to thank my fellow readers for their great suggestions. Much appreciated. Thanks, B2
        Message 3 of 7 , May 5, 2008
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          Just a note to thank my fellow readers for their great suggestions.
          Much appreciated. Thanks,

          B2

          --- In AirWire@yahoogroups.com, "Bruce K. Bates" <birdwater@...> wrote:
          >
          > Do any of you have any experience with battery indicators? I love
          > using my Airwire equiped engines with on board batteries, but get
          > perturbed wien they take on a mind of their own, due to a low battery.
          > It would b enice to be able to have a visual indicaiton of the "Fuel"
          > remaiining so that I cold get the engine back to a serviceing area
          > before it dies.
          >
          > Any suggestions?
          >
          > Bruce
          >
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