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Headlight Reminder

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  • multiuseguy <multiuseguy@yahoo.com>
    Request if anyone can provide a simple headlight reminder circuit so I can tell when my headlights are left on when the engine is off. Thanks.... MUG
    Message 1 of 3 , Dec 7, 2002
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      Request if anyone can provide a simple headlight reminder circuit so
      I can tell when my headlights are left on when the engine is off.
      Thanks.... MUG
    • Brian Hoskins
      Hello multiuseguy That s a pretty simple little problem actually. All you need to do is delve into the fuse box of your vehicle and find a fuse which is live
      Message 2 of 3 , Dec 8, 2002
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        Hello multiuseguy

        That's a pretty simple little problem actually. All you need to do is delve
        into the fuse box of your vehicle and find a fuse which is live (+12V) when
        the engine is on and off (0V) when the engine is off (there'll be a good
        couple of those there) and then use that as the input to a CMOS NOT gate.
        You can use TTL but you'd have to do some signal conditioning then because
        the output from the vehicle fuse box is +12V and TTL requires 0-5V.

        Then you need to take an output from the headlight switch, so that when the
        switch is on you have 12V on your output. Use this as the input to an AND
        Gate, and use the output of your NOT gate as the 2nd Input to the AND gate.
        That's it in a nutshell - the AND gate will now output 12V when you've
        left your lights on and the Engine is off, and 0V when the lights are on
        and the Engine is on. All you need to do now is design a suitable output
        stage, wether it be a simple flashing light or a buzzer. You'll need a
        buffering stage on the output mind, because a CMOS gate will not be capable
        of driving any sort of real load.

        If you want me to provide you with Truth Tables and Boolean Algebra
        statements to show you why that works, then let me know and I'll draw it up
        for you. It's very simple to do. Do you have any experience at all with
        Electronics?





        -----
        Brian J Hoskins
        South Wales, UK

        Email: BrianJHoskins@...
        Mobile: 07967 240380

        Amiga 040/PPC, Amiga OS3.9.
        -----
      • multiuseguy <multiuseguy@yahoo.com>
        Hello Brian, If something is drawn out for me and it is correct then I know enought to wire it up. But if for some reason the circuit would not work I would
        Message 3 of 3 , Dec 9, 2002
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          Hello Brian,

          If something is drawn out for me and it is correct then I know
          enought to wire it up. But if for some reason the circuit would not
          work I would have no idea where to start to look for the problem.
          Say for instance is a resistor value might need to be tweaked, I
          would have no idea that that would be necessary. I figured out how
          to do this with a couple of relays but that seems very backward as
          one relay must always be drawing current and I don't know how long
          that relay might last.

          M.U.G.


          --- In Electronics_101@yahoogroups.com, Brian Hoskins
          <BrianJHoskins@u...> wrote:
          > Hello multiuseguy
          >
          > That's a pretty simple little problem actually. All you need to do
          is delve
          > into the fuse box of your vehicle and find a fuse which is live
          (+12V) when
          > the engine is on and off (0V) when the engine is off (there'll be a
          good
          > couple of those there) and then use that as the input to a CMOS NOT
          gate.
          > You can use TTL but you'd have to do some signal conditioning then
          because
          > the output from the vehicle fuse box is +12V and TTL requires 0-
          5V.
          >
          > Then you need to take an output from the headlight switch, so that
          when the
          > switch is on you have 12V on your output. Use this as the input to
          an AND
          > Gate, and use the output of your NOT gate as the 2nd Input to the
          AND gate.
          > That's it in a nutshell - the AND gate will now output 12V when
          you've
          > left your lights on and the Engine is off, and 0V when the lights
          are on
          > and the Engine is on. All you need to do now is design a suitable
          output
          > stage, wether it be a simple flashing light or a buzzer. You'll
          need a
          > buffering stage on the output mind, because a CMOS gate will not be
          capable
          > of driving any sort of real load.
          >
          > If you want me to provide you with Truth Tables and Boolean Algebra
          > statements to show you why that works, then let me know and I'll
          draw it up
          > for you. It's very simple to do. Do you have any experience at
          all with
          > Electronics?
          >
          >
          >
          >
          >
          > -----
          > Brian J Hoskins
          > South Wales, UK
          >
          > Email: BrianJHoskins@u...
          > Mobile: 07967 240380
          >
          > Amiga 040/PPC, Amiga OS3.9.
          > -----
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