[Tex/LaTex] TikZ: Use –cycle in circuits

tikz-pgf

Why does the --cycle command doesn’t work in a circuit drawn with the TikZ library circuits.ee.IEC? The problem with manually draw the last connection is that the ends are not joined.

problem
_{I made the lines very thick to demonstrate the problem of not joining …}

Is it possible to fix this or at least join the path manually?

Code

\documentclass{minimal}

\usepackage{tikz}
\usetikzlibrary{circuits.ee.IEC}

\begin{document}
\begin{tikzpicture}[circuit ee IEC, line width=5pt]
\draw (0,0) -- ++(0,2) node [above] {without objects}%
    -- ++(4,0) -- ++(0,-2)%
    --cycle node [below] {works};

\draw (0,-4.5) to[voltage source] ++(0,2) node [above] {with -\/-cycle}%
    -- ++(4,0) to[resistor] ++(0,-2)%
    --cycle node [below] {no connection};

\draw (0,-9) to[voltage source] ++(0,2) node [above] {manually}%
    -- ++(4,0) to[resistor] ++(0,-2)%
    -- ++(-4,0) node [below] {not joined};
\end{tikzpicture}
\end{document}

Best Answer

The manual on the --cycle operation:

This operation adds a straight line from the current point to the last point speciﬁed by a move-to operation. Note that this need not be the beginning of the path. Furthermore, a smooth join is created.

So apparently there is a move-to operation when the voltage source and resistor are added (which makes perfect sense) therefore the cycle is actually made, only it just draws a line back to the end of the resistor in this case over the line that's already there.

I can't think of any way to fix this behaviour, a move has to be made in the pgf path in order to 'skip' the symbol for the resistor (and voltage source). We can perform a little trick to get a proper join when adding the line manually though. Basically what we do is just draw a short line up over the one already there, this will create a smooth join on top of what's already there.

\documentclass{minimal}

\usepackage{tikz}
\usetikzlibrary{circuits.ee.IEC}

\begin{document}
\begin{tikzpicture}[circuit ee IEC, line width=5pt]
\draw (0,0) -- ++(0,2) node [above] {without objects}%
    -- ++(4,0) -- ++(0,-2)%
    --cycle node [below] {works};

\draw (0,-4.5) to[voltage source] ++(0,2) node [above] {with -\/-cycle}%
    -- ++(4,0) to[resistor] ++(0,-2)%
    --cycle node [below] {no connection};

\draw (0,-9) to[voltage source] ++(0,2) node [above] {manually}%
    -- ++(4,0) to[resistor] ++(0,-2)%
    -- ++(-4,0) node [below] {now joined} -- ++(0,0.1);
\end{tikzpicture}
\end{document}

And the resulting document:

Joined lines in circuit

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In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
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  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
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}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
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    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
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\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
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  }
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\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

[Tex/LaTex] Labeling a circuit element with its symbol and value on both sides

Old question, but in the time since it was asked an improvement has been made to CircuiTikz to allow this behavior.

Since Version 0.7, beside the original label (l) option, there is a new option to place a second label, called annotation (a) at each bipole. Up to now this is a beta-test and there can be problems. For example, up to now this option is not compatible with the concurrent use of voltage labels.

The position of (a) and (l) labels can be adjusted with _ and ^, respectively.

MWE:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows, circuits.ee.IEC, positioning}
\usepackage[american voltages, american currents,siunitx]{circuitikz}

\begin{document}
\begin{tikzpicture}[circuit ee IEC,american,x=2cm,y=2cm, semithick, every info/.style={font=\footnotesize}, small circuit symbols, set resistor graphic=var resistor IEC graphic]
        \draw (0,0) node[shape=ground]{}
    to [V, invert, l=\mbox{$V_S$}, a={\SI{5}{\volt}}] (0,1)
    to [cspst , l =$t_0$] (1,1)
    to [L, l=\mbox{$L$}, a=\SI{1}{\henry}] (2,1)
    to [R, l=\mbox{$R$}, a=\SI{47}{\ohm}] (3,1)
    to [C, l_=\mbox{$C$}, a^=\SI{247}{\pico\farad}] (3,0)
    to (3,0) node[shape=ground]{};
\end{tikzpicture}
\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

[Tex/LaTex] Labeling a circuit element with its symbol and value on both sides

MWE:

Result:

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