circuitikz: Adding arrowhead to tap of variable inductance?

Question

I'd like the tap of a variable inductor to have an arrowhead, like for a variable resistor or potentiometer, as shown below. Any suggestions on how to add this? I've tried "->" with and without "to[short,...". I've tried "-A". What am I forgetting?

\documentclass{standalone}
\usepackage[utf8]{inputenc}
\usepackage[siunitx, RPvoltages]{circuitikz}
\begin{document}
\pagestyle{empty}
\begin{circuitikz}[american]
  \draw (0,0) to[L, name=L, mirror] ++(0,-2) coordinate(tap) -- ++(0,-1);
  \draw (tap) -- ++(1,0) coordinate(end) -- (L.midtap -| end) -- (L.midtap);
  \draw (0,-3) to[potentiometer, name=R] ++(0,-2) coordinate(tapR) -- ++(0,-1);
  \draw (tapR) -- ++(1,0) coordinate(endR) -- (R.wiper -| endR) -- (R.wiper);
\end{circuitikz}
\end{document}

Thanks for any help and suggestions.

-Kevin

I took a liberty to correct title of question – Zarko Oct 11 '22 at 00:14 — Zarko, Oct 11 '22 at 00:14

Zarko · Accepted Answer · 2022-10-11T11:19:16.760

6

A possible (rude) solution is:

\documentclass[margin=3mm]{standalone}
\usepackage[siunitx, RPvoltages]{circuitikz}
\usetikzlibrary[arrows.meta]
\begin{document}
\begin{circuitikz}[american]
\draw (0,0) to [short,-*]   ++ (0,1)  coordinate (a)
            to [L, name=L]  ++ (0,2);
\draw[Stealth-]   (L.center) --  ++ (1,0)   |-  (a)
            ;
\end{circuitikz}
\end{document}

Edit:
Instead of use coordinate (L.center), which in this particular case works fine, is more correct to use (L.midtap), which works at any shape for inductance (see @rmano answer):

\begin{circuitikz}[american]
\draw (0,0) to [short,-*]   ++ (0,1)  coordinate (a)
            to [L, name=L]  ++ (0,2);
\draw[Stealth-]   (L.midtap) --  ++ (1,0)   |-  (a)
            ;
\end{circuitikz}

edited Oct 11 '22 at 11:19

answered Oct 10 '22 at 20:55

Zarko

296,517

That doesn't seem rude at all. It seems perfect. Thanks so much. – Kevin Zembower Oct 10 '22 at 21:48
But it is not exactly the same arrow ... still +1, because it is better to use a real arrow tip. – Jasper Habicht Oct 11 '22 at 08:09
1

@JasperHabicht, I added that issue to my answer. See also https://tex.stackexchange.com/a/549354/38080 – Rmano Oct 11 '22 at 08:25

Rmano · Answer 2 · 2022-10-11T08:32:56.137

@Zarko's answer is the correct way to do it. I would suggest using the midtap anchor and judicious use of mirror to make it general for other L-shapes.

Notice that the use of mirror is a bit of an "adjust it" thing, because it depends on the shape and on how many "loops" you have in the inductance...

\documentclass[margin=2.718mm]{standalone}
\usepackage[siunitx, RPvoltages]{circuitikz}
\usetikzlibrary[arrows.meta]
\begin{document}
\begin{circuitikz}[]
\draw (0,0) to [short,-*]   ++ (0,1)  coordinate (a)
            to [L, mirror,  name=L]  ++ (0,2);
\draw[Stealth-]   (L.midtap) --  ++ (1,0)   |-  (a);
\begin{scope}[american, xshift=3cm]
\draw (0,0) to [short,-*]   ++ (0,1)  coordinate (a)
            to [L, name=L]  ++ (0,2);
\draw[Stealth-]   (L.midtap) --  ++ (1,0)   |-  (a);
\end{scope}
\begin{scope}[american, xshift=6cm, 
    circuitikz/inductors/coils=5]
\draw (0,0) to [short,-*]   ++ (0,1)  coordinate (a)
            to [L, mirror, name=L]  ++ (0,2);
\draw[Stealth-]   (L.midtap) --  ++ (1,0)   |-  (a);
\end{scope}
\begin{scope}[european, xshift=9cm]
\draw (0,0) to [short,-*]   ++ (0,1)  coordinate (a)
            to [L, mirror, name=L]  ++ (0,2);
\draw[Stealth-]   (L.midtap) --  ++ (1,0)   |-  (a);
\end{scope}
\end{circuitikz}
\end{document}

If you want the same "fake" arrow of the rest of circuitikz(*), you can:

\documentclass[margin=2.718mm]{standalone}
\usepackage[siunitx, RPvoltages]{circuitikz}
\usetikzlibrary[arrows.meta]
\begin{document}
\begin{circuitikz}[]
\draw (0,0) to [short,-*]   ++ (0,1)  coordinate (a)
            to [L, mirror,  name=L]  ++ (0,2);
            \draw[]   (L.midtap) node[inputarrow, xscale=-1]{} 
            --  ++ (1,0)   |-  (a);
\end{circuitikz}
\end{document}

(*) For a bit more details about arrows in circuitikz, see https://tex.stackexchange.com/a/549354/38080

Thank you for your answer (+1). I tried to use ˙.midtap` option but it didn't work for me :-(. Now I figured out why -- I wrongly spell this option name ... — Zarko, Oct 11 '22 at 11:21
@Rmano, thank you very much for your answer, and for all your work on circuitikz. I'm really enjoying learning this system. Thanks, also, for teaching me the simplified line drawing in "-- ++(1,0) |- (a)" which I"m sure is in the pgftikz manual, but I didn't learn about it until now. — Kevin Zembower, Oct 11 '22 at 13:35
Thanks! It's called perpendicular coordinate system: https://tikz.dev/tikz-coordinates#sec-13.3.1 — Rmano, Oct 11 '22 at 13:42
@Rmano, thanks. I do know about "perpendicular coordinates." They would be written like I did, as "(R.wiper -| endR)". But, you wrote, "\draw[] (L.midtap) node[inputarrow, xscale=-1]{} -- ++ (1,0) |- (a)" which, in English, I interpret as "draw the arrowhead at the L midtap, then draw a line one unit right, then, from this point, USING ONLY horizontal and vertical lines (first horizontal, then vertical) write a line to point a." That was the part that was new to me. Thanks, again. — Kevin Zembower, Oct 11 '22 at 14:24
Ah, yes. You could be interested by https://tex.stackexchange.com/questions/45347/vertical-and-horizontal-lines-in-pgf-tikz also.... — Rmano, Oct 11 '22 at 14:43

circuitikz: Adding arrowhead to tap of variable inductance?

2 Answers2