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Re: Lighting question

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  • Matthew Gatof DVM
    ... Bob, I built a board as per your diagram, and it works. However, when I use 5mm warm white LED s on the headlight circuit they glow very dimly when they
    Message 1 of 10 , Aug 12, 2007
      --- In AirWire@yahoogroups.com, "Bob Small" <rds@...> wrote
      >
      > I have added a diagram in the Files section.

      Bob,

      I built a board as per your diagram, and it works. However, when I use
      5mm warm white LED's on the headlight circuit they glow very dimly when
      they are supposed to be off. I am not sure they are supposed to do
      this (I don't see any information in the airwire decoder that allows it
      to conform to Rule 17--dimming of the headlights). Interestingly, when
      I place a 3mm super bright white LED in its place it goes off properly.

      I am using the following components: the diodes you reccomended
      1n4001, the resistors on the headlight circuit are 470 ohm resistor in
      series with 2 7000mcd 20mA 3.2V warm white 5mm leds (this is with the
      lamps glowing) or the same resistor with 2 3000mcd 20mA 3.6V regular
      white 3mm leds (off completely). Any thoughts as to why this is
      happening. Oh yah, I am running a 14.4 V NIMH battery pack.

      Hope I gave you enough information.

      Thanks for everyones help--I am really having fun with this, and I was
      so impressed with myself when the lights came on and went off with the
      throttle! What a blast.

      Matt
    • Bob Small
      Hi Matt, Glad you enjoy it. I had a close look at my NW2. And I see exactly what you describe. The off light is actually very slightly on. Instead of being
      Message 2 of 10 , Aug 12, 2007
        Hi Matt,

        Glad you enjoy it.

        I had a close look at my NW2. And I see exactly what you describe.
        The "off" light is actually very slightly on. Instead of being totally
        clear it is a sort of milky white.

        Obviously there is a very slight current leak somewhere, and, as you
        have discovered, some LEDs will be slightly "on" with this small
        current.

        I don't know if I can measure this very small current (I only have very
        basic electronic equipment) but I'll setup a test AirWire with a couple
        of LEDs and investigate.
      • Matthew Gatof DVM
        ... totally ... Glad I am not imagining it. It is actually somewhat prototypical, if not exactly right for something called Rule 17. If I understand the
        Message 3 of 10 , Aug 12, 2007
          --- In AirWire@yahoogroups.com, "Bob Small" <rds@...> wrote:
          >
          > Hi Matt,
          >
          > Glad you enjoy it.
          >
          > I had a close look at my NW2. And I see exactly what you describe.
          > The "off" light is actually very slightly on. Instead of being
          totally
          > clear it is a sort of milky white.
          >


          Glad I am not imagining it. It is actually somewhat prototypical, if
          not exactly right for something called "Rule 17." If I understand
          the rule correctly it requires the dimming of the headlight when a
          train is sitting idle--not copletely off. So for my pruposes I am
          not sure I will correct the "problem." Though I would like to know
          where the problem is--though if it is in the airwire board, not much
          I could do about that I guess.

          Thanks for the reply, I await the results of your tests.

          When this thing is done I'll try and post some pictures--maybe next
          YEAR!!!!!

          Matt
        • Bob Small
          I had a quick look but don t know that I ve come up with much. I don t think the problem is with the AirWire. If the lights are switched off (F0) then there is
          Message 4 of 10 , Aug 17, 2007
            I had a quick look but don't know that I've come up with much.

            I don't think the problem is with the AirWire. If the lights are
            switched off (F0) then there is no "whiteness" in the LEDs, so I assume
            that there is no current leakage through TM4-1 or 2.

            So the only other leakage path is through one of the "constant lighting
            diodes". The 1N4148 has a reverse leakage around 25nA and a 1N4001 is
            around 5uA. The white LEDs must be sensitive to this very small current.
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