Re: What does Rail Mean ?
From: Chretien (Cretian_at_123.com)
Date: 02/16/05
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Date: Wed, 16 Feb 2005 16:58:26 -0600
"Roger Johansson" <no-email@home.se> wrote in message
news:Xns95FFDF745B02186336@130.133.1.18...
> "Chretien" <Cretian@123.com> wrote:
>
> > Maybe the concept is over my head to understand ??
>
> It is more likely that it goes under your head, this is a very simple
> concept.
>
> When we need to distribute power to all circuits on a pcb we often make
> long straight "rails" of metal, or a copper trace along one border of
> the pcb, or in a snakelike pattern.
>
> (really new pcb's are laminated, and the rails are now complete planes of
> copper inside the pcb)
>
> When we draw circuits on paper we usually draw a horisontal line across
> the top of the circuit and we use that as the positive voltage from the
> power supply. There is often also a horisontal line at the bottom of the
> circuit, to show the ground connections.
>
> (Another alternative is to draw a grounding symbol everywhere where
> something is connected to ground. All these ground symbols are in reality
> connected to each other, in a car it is the chassi which is ground, or
> the neutral rail)
>
> This is sometimes also how we lay out circuits in reality, on pcb's.
>
> So we have come to refer to these power supply rails as rails. It means
> just that, a long piece of metal, or a long, wide, copper trace which
> carries electrical power to many circuits on a pcb.
>
> > Here is a diagram of
> > what I think you said. The wire between the resistors and light would
> > not be considered Rail. or am I all wrong.
> >
> >
> >
> >
> >
> > ___ ___
> > o------Rail-----|___|--|___|--.
> > |
> > ,---.
> > | X |Light
> > '---'
> > |
> > |
> > o-----Rail--------------------'
> >
>
> The lower rail is a real rail.
> The upper dotted line is not a rail along all of its length, because the
> wire/rail is interrupted by resistors. The upper line is thus only a rail
> until it comes to the first resistor. The points after the resistor are
> not in direkt contact with the plus pole of the battery.
>
> A real rail carries the same voltage as the power supply, along all its
> length. It is a direct contact to the power source.
>
>
> --
> Roger J.
Roger thanks I get this. And its what I ment (perhaps not properly said)
when I said anything between the components is not rail. Your clarification
would be everything starting with the first component to the last is not
rail. I think thats what you said anyway.
Thankyou.
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