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Re: Headlight Reminder

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  • 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 1 of 3 , Dec 8, 2002
      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 2 of 3 , Dec 9, 2002
        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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