Normalizing the dimensions of a DC motor circuit schematic - TeX

Diaa replying to marmot

Please, have a look at my follow-up question here https://topanswers.xyz/tex?q=1581.

marmot replying to Diaa

Here is a very basic version. On the long run you probably need also something for curves.  
```  
\documentclass[tikz,border=3mm]{standalone}
\usetikzlibrary{arrows.meta}
\tikzset{pics/flow arrow/.style={code={\tikzset{flow arrow pars/.cd,#1}
	\def\pv##1{\pgfkeysvalueof{/tikz/flow arrow pars/##1}}	
	\draw[/tikz/flow arrow pars/arrow,
		to path={(\tikztostart)--(\tikztotarget) \tikztonodes}] (-\pv{l}/2,\pv{d}) 
		to[edge label={\pv{t}},edge label'={\pv{t'}},allow upside down=false]
	(\pv{l}/2,\pv{d});
}},flow arrow/.style={to path={
 (\tikztostart) -- pic[sloped,allow upside down]{flow arrow={#1}} (\tikztotarget)}},
 flow arrow pars/.cd,
	l/.initial=2em,d/.initial=1.5ex,arrow/.style={-Latex},t/.initial={},t'/.initial={}}
\begin{document}
\begin{tikzpicture}[x=3em,y=3em]
 \draw (0,0) -- pic{flow arrow={t={$I_a$}}} ++(1,0);
 \draw (2,0) -- pic{flow arrow={t'={$I_a$},d=-2ex}} ++(1,0);
 \draw (4,0) -- pic{flow arrow={t={$I_a$},arrow/.style={-Stealth}}} ++(1,0);
 \draw[thick] (6,0) -- pic{flow arrow={t=$I_a$}} ++(1,0);
 
 \begin{scope}[yshift=-8em]
 \draw (0,0) to[flow arrow={t={$I_a$}}] ++(1,1);
 \draw (2,0) to[flow arrow={t'={$I_a$},d=-2ex}] ++(1,0.5);
 \draw (4,0) to[flow arrow={t={$I_a$},arrow/.style={-Stealth}}] ++(1,-0.5);
 \draw[thick] (8,0) to[flow arrow={t={$I_a$}}] ++(-1,0.5);
 \end{scope}
\end{tikzpicture}
\end{document}  
```  
![Screen Shot 2020-12-25 at 12.48.11 PM.png](/image?hash=b8c082b72a591955404a0eabf141e9c7a07662bf47261624bdd55f34760b2f54)

Diaa replying to marmot

if you can have a key or option in the `to [ ]` command to draw a parallel arrow (with the ability to pass the typical style options of any regular arrow)), it would be awesome

Diaa replying to marmot

I did it this way, but I am sure the code can be prettified and simplified a lot  
```  
\draw[thick] (0,2) coordinate[label={[yshift=-0.5ex]below:{$+$}}] (TL)to[ R=$R_a$, name=Ra, o-] ++(2,0) 
			to[short]  ++(0.1,0) 
			to[L,cute inductor, l=$L_a$, name=La, -.]  ++(2,0)  
			to[Telmech=M, name=M1] ++(0,-2) 
			to[short,.-o] (0,0)	coordinate[label={[yshift=-0.5ex]above:{$-$}}] (ML);
			\draw[-Latex] ([shift={(0.15, 0.2)} ] Ra.east) -- ([shift={(-0.15, 0.2)}] La.west) node[midway,  yshift=2ex] {$I_a$};  
```    
![blob](/image?hash=9f0357fb8ee6ae37c15905721b38a9165cfd0ff5938b190dba33cb83722d090b)

marmot replying to Diaa

Yes, that explains a lot. So `circuitikz` is an organically grown package and the elements in there may or may not be precisely what one wants. (It isn't too difficult to add an arrow parallel to a path via a `pic`, say, or a style that adds a `pic`..)

Diaa

Seemingly, it is better to avoid using the flow arrow and replace it a labelled arrow.

Diaa

@marmot, re: [your answer](#a1827),  FYI, I received this response from Rmano on tex.se:  
  
"The flow arrow is not a TikZ arrow, it is a shape, so you can't scale its parts differently. You can use the "advanced flows" to build your own arrow, see the manual, section 4.8, around pag 158, and tex.stackexchange.com/a/549354/38080 See also https://tex.stackexchange.com/q/574576/2288 for an example application"

marmot replying to Diaa

During hibernation season there is no real distinction between day and night for marmots. :smile_cat:

Diaa replying to marmot

You are right, both worked but without effect on the flow arrow size since the flow arrow is a node not real arrow as quoted from  `pgfcircflow.tex`.  
I think that's the end of my journey unless Rmano shows up.  
  
Have a nice night (I guess :))

marmot replying to Diaa

In my case it is defined but I get an arithmetic overflow error. This is because the "natural" scale here is not `1` but `16`. (Why `16`? I do not know.) Also I have no intuition for this key but `to[short,f=$i_a$,current arrow scale=16/\myscale]` or `to[short,f=$i_a$,current arrow scale=16*\myscale]` do not cause errors on my machine. Please also note that in principle arrow heads should scale with the line width.  And you're welcome! :smile_cat:

Diaa replying to marmot

May I know why does this `to[short, f=$i_a$, current arrow scale = \myscale]` fail?  
Isn't `\myscale` globally  accessed?

Diaa replying to marmot

It is really enjoyable to TeXting with you :D  
My problem was solved a couple of codes before but your knowledge is tempting to ask for more.  
My code goes from good to better.  
Thanks for the help.

marmot replying to Diaa

I may be able to partially understand this code but I am not sure. Seems like you want to rescale `\pgf@circ@Rlen`. So one has to find the code that sets it, which seems to be `pgfcirc.defines.tex`, manipulate it, and see if this helps. However, I think this is a very dangerous game which may result in more trouble than benefits. So, unless one wants to read the manual and source code carefully, the best bet would be to ask an expert like Rmano.

marmot replying to Diaa

This problem can be repaired with   
```  
\tikzset{every picture/.append style={%
        execute at begin picture={\pgfmathsetmacro{\myscale}{1ex/\oriex}%
            \ctikzset{bipoles/thickness=1,
                resistors/scale=\myscale, capacitors/scale=\myscale,
                diodes/scale=\myscale, transistors/scale=\myscale,
                grounds/scale=\myscale, csources/scale=\myscale,
                sources/scale=\myscale, batteries/scale=\myscale,
                instruments/scale=\myscale, inductors/scale=\myscale,
                electromechanicals/scale=\myscale,
                %current arrow scale=16*\myscale*\myscale,%<-?
                mechanicals/scale=\myscale, use fpu reciprocal}%
            \tikzset{line width= {\myscale*0.4pt}, x=1cm*1em/\oriem,
			y=1cm*1ex/\oriex,
			ultra thin/.style={line width=\myscale*0.1pt},
			very thin/.style={line width=\myscale*0.2pt},
			thin/.style={line width=\myscale*0.4pt},
			semithick/.style={line width=\myscale*0.6pt},
			thick/.style={line width=\myscale*0.8pt},
			very thick/.style={line width=\myscale*1.2pt},
			ultra thick/.style={line width=\myscale*1.6pt}			
			}}}}  
```    
Why? Because `thick` and friends are defined with an explicit line width in point. (I just copied these definitions from `tikz.code.tex` and multiplied them by `\myscale`.) That means that, if you want to go this route, there may be many other things that also have explicit fixed dimensions in their definitions. And of course it is not sufficient to just scan `tikz.code.tex` for `pt`.

Diaa replying to marmot

This code is so beautiful but it needs to accordingly scale the line width (and its friends `thick`, `very thick`, etc) to NOT have this weird output when using  `\tiny`  
  
https://pastebin.com/ih9jn9WH  
  
![blob](/image?hash=97b3a5c894f946cbb2399ad7736fe4b37557954dde7c379006ebff0b62f880cb)

Diaa replying to marmot

I think the node of the flow arrow can be hacked or replaced by a scalable one to go in sync with the font size.

Diaa replying to marmot

I found this in the file `pgfcircflow.tex` of circuitikz package but it looks like sorcery to me :D :  
  
```  
  \pgfextra{
        \newdimen{\absfshift}
        \def\flow@offset{\ctikzvalof{flow/offset}\pgf@circ@Rlen}
        \absfshift=\flow@offset
        \ifpgf@circuit@bipole@flow@backward
            \pgfmathsubtract{\pgf@circ@rounded@dir}{180}
            \edef\pgf@circ@rounded@dir{\expandafter\pgf@circ@stripdecimals\pgfmathresult\pgf@nil}
        \fi
    }
    \ifpgf@circuit@bipole@flow@below
        coordinate (pgfcirc@Ffrom@up) at ($(pgfcirc@Ffrom@flat) ! \absfshift !-90: (pgfcirc@Fto@flat)$)
        coordinate (pgfcirc@Fto@up) at ($(pgfcirc@Fto@flat) ! \absfshift !90: (pgfcirc@Ffrom@flat)$)
    \else
        coordinate (pgfcirc@Ffrom@up) at ($(pgfcirc@Ffrom@flat) ! \absfshift !90: (pgfcirc@Fto@flat)$)
        coordinate (pgfcirc@Fto@up) at ($(pgfcirc@Fto@flat) ! \absfshift !-90: (pgfcirc@Ffrom@flat)$)
    \fi
    coordinate (\pgfcirc@a@prefix-Fpos) at ($(pgfcirc@Ffrom@up) ! \ctikzvalof{flow/distance} !(pgfcirc@Fto@up)$)
    \pgfextra{
        \absfshift=0.25\pgf@circ@Rlen% This is half size of the "flowarrow" shape!
    }
    coordinate (\pgfcirc@a@prefix-Ffrom) at ($(\pgfcirc@a@prefix-Fpos)!\absfshift!(pgfcirc@Ffrom@up)$)
    coordinate (\pgfcirc@a@prefix-Fto) at ($(\pgfcirc@a@prefix-Fpos)!\absfshift!(pgfcirc@Fto@up) $)
    %
    % coordinate (\pgfcirc@a@prefix-Fpos) at
    %     ([yshift=\flow@offset]$(\pgfcirc@a@prefix-Ffrom)! \ctikzvalof{flow/distance} !(\pgfcirc@a@prefix-Fto)$)
    % if the flow label is not empty (in which case we have already all the anchors)
    \pgf@circ@ifkeyempty{bipole/flow/label/name}\else
        % the flow arrow is really a node "flowarrow", not a real arrow
        node[flowarrow, rotate=\pgf@circ@rounded@dir, anchor=center](Farrowpos) at (\pgfcirc@a@prefix-Fpos) {}

        node[anchor=\pgf@circ@dir, \circuitikzbasekey/bipole flow style]
        (\ctikzvalof{bipole/name}flow) at (Farrowpos.\pgf@circ@bipole@flow@label@where) {\pgf@circ@finallabels{flow/label}}
    \fi
```

marmot replying to Diaa

An arguably better way could be the following. But I struggle to find the right key to scale the arrows. Since there is a key named `current arrow scale`, there should be a way, but I am not sure what "current" means in this context, contemporary or flow of electric charge.  
```   
\documentclass{article}
\usepackage[
american, 
siunitx , 
RPvoltages, 
]{circuitikz}

\pgfmathsetmacro{\oriex}{1ex}% store the height of an x in normalsize
\pgfmathsetmacro{\oriem}{1em}
\tikzset{every picture/.append style={%
execute at begin picture={\pgfmathsetmacro{\myscale}{1ex/\oriex}%
\ctikzset{bipoles/thickness=1,
	resistors/scale=\myscale, capacitors/scale=\myscale,
	diodes/scale=\myscale,transistors/scale=\myscale,
	grounds/scale=\myscale,csources/scale=\myscale,
	sources/scale=\myscale,batteries/scale=\myscale,
	instruments/scale=\myscale,
	%current arrow scale=16*\myscale*\myscale,%<-?
	mechanicals/scale=\myscale,use fpu reciprocal}%
\tikzset{line width={\myscale*0.4pt},x=1cm*1em/\oriem,y=1cm*1ex/\oriex}}}}
\begin{document}
    \tiny $R_a$ for comparison \par
    \begin{circuitikz}		
        \draw (0,2) to[R=$R_a$, o-] ++(2,0)
        to[short,f=$i_a$] ++(0.1,0) 
        to[L, cute inductor, l=$L_a$]  ++(2,0);
    \end{circuitikz}\par\medskip

    \normalsize $R_a$ for comparison \par
    \begin{circuitikz}
        \draw (0,2) to[R=$R_a$, o-] ++(2,0)
        to[short,f=$i_a$] ++(0.1,0) 
        to[L, cute inductor, l=$L_a$]  ++(2,0);
    \end{circuitikz}\par\medskip

    \Large $R_a$ for comparison \par
    \begin{circuitikz}
        \draw (0,2) to[R=$R_a$, o-] ++(2,0)
        to[short,f=$i_a$] ++(0.1,0) 
        to[L, cute inductor, l=$L_a$]  ++(2,0);
    \end{circuitikz}\par\medskip
\end{document}
```  
![Screen Shot 2020-12-24 at 6.09.08 PM.png](/image?hash=6b04b3d70e9ab91ffcb85ba4e0e77922100b638f6d61d1ac0f6c42326fddfac5)

marmot

This is IMHO a tiny bit better but still far from good.  
```  
\documentclass{article}
\usepackage[
american, 
siunitx , 
RPvoltages, 
]{circuitikz}

\pgfmathsetmacro{\oriex}{1ex}% store the height of an x in normalsize
\tikzset{every picture/.append style={%
execute at begin picture={\pgfmathsetmacro{\myscale}{1ex/\oriex}%
\ctikzset{bipoles/thickness=\myscale}%
\tikzset{line width={\myscale*0.4pt},scale=\myscale,node font=\normalsize,
transform shape, use fpu reciprocal}}}}
\begin{document}
    \tiny $R_a$ for comparison \par
    \begin{circuitikz}		
        \draw (0,2) to[R=$R_a$, o-] ++(2,0)
        to[short,f=$i_a$] ++(0.1,0) 
        to[L, cute inductor, l=$L_a$]  ++(2,0);
    \end{circuitikz}\par\medskip

    \normalsize $R_a$ for comparison \par
    \begin{circuitikz}
        \draw (0,2) to[R=$R_a$, o-] ++(2,0)
        to[short,f=$i_a$] ++(0.1,0) 
        to[L, cute inductor, l=$L_a$]  ++(2,0);
    \end{circuitikz}\par\medskip

    \Large $R_a$ for comparison \par
    \begin{circuitikz}
        \draw (0,2) to[R=$R_a$, o-] ++(2,0)
        to[short,f=$i_a$] ++(0.1,0) 
        to[L, cute inductor, l=$L_a$]  ++(2,0);
    \end{circuitikz}\par\medskip
\end{document}  
```

marmot replying to Diaa

I am afraid that I do not like the answer. It "over transforms things", i.e. it makes fonts tiny and transforms a second time. (I think it is also unnecessarily complicated.) Please look at  
```  
\documentclass{article}
\usepackage[
american, 
siunitx , 
RPvoltages, 
]{circuitikz}

\newcommand{\tinyscale}{0.5}
\newcommand{\Largescale}{1.5}

\begin{document}
    \tiny some text for comparison $R_a$
    \ctikzset{bipoles/thickness=\tinyscale}
    \begin{circuitikz}[scale=\tinyscale, transform shape, use fpu reciprocal, line width={\tinyscale*0.5pt}]
        \draw (0,2) to[R=$R_a$, o-] ++(2,0)
        to[short,f=$i_a$] ++(0.1,0) 
        to[L, cute inductor, l=$L_a$]  ++(2,0);
    \end{circuitikz}

    \normalsize some text for comparison $R_a$
    \ctikzset{bipoles/thickness=1}
    \begin{circuitikz}
        \draw (0,2) to[R=$R_a$, o-] ++(2,0)
        to[short,f=$i_a$] ++(0.1,0) 
        to[L, cute inductor, l=$L_a$]  ++(2,0);
    \end{circuitikz}

    \Large some text for comparison $R_a$
    \ctikzset{bipoles/thickness=\Largescale}
    \begin{circuitikz}[scale=\Largescale, transform shape, use fpu reciprocal, line width={\Largescale*0.5pt}]
        \draw (0,2) to[R=$R_a$, o-] ++(2,0)
        to[short,f=$i_a$] ++(0.1,0) 
        to[L, cute inductor, l=$L_a$]  ++(2,0);
    \end{circuitikz}
\end{document}  
```  
  
![Screen Shot 2020-12-24 at 5.16.25 PM.png](/image?hash=c4e0c9d2476f1818da9bdc22302925c597c5e3eecf518a2319b55a86deea743f)  
  
As you can see, it effectively squares the transformation, i.e. instead of `1/2`, say, you get `1/4`. This is because of how `transform shape` works. And this why I thought it would be good to as Rmano. There should be something that just scales the length of the circuit elements without scaling the texts.

Diaa

@marmot, re: [your answer](#a1827),  Is it possible  to employ this answer I got https://tex.stackexchange.com/a/576289/2288 with your beautiful codes to have a complete circuit with bricks pattern that can be scaled by either font size or `adjustbox`? Or am I talking about something tedious, fragile and not worth the effort?

marmot replying to Diaa

Well, sure. There is a chance that one can add a `force recompile` option here, ironically the problem is very analogous to `externalize`: if you use `em` units in a picture, say, and the font size changes, `externalize` "thinks" : "Well, this input I already compiled in a previous run, so nothing to do.". Similarly for patterns, if you had used one with `em` units Ti*k*Z thinks that you are using an old one and does not recalibrate it. (At least a brute force solution is possible, I think.)

Diaa replying to marmot

Your great pattern addendum should be highlighted in a new answer.  
Would you like to move it to a new Q/A?

marmot replying to Diaa

This one scales the patterns. (One has to use tricks like `1.01em` so that Ti*k*Z does not think it has done this already an just keeps what it has had before. In some way this is a bug.) Note, however, that the pattern offset is not synchronized. (Can be done, even more efforts.)  (I had to move the code to the answer because it would not fit in the comments.)

marmot replying to Diaa

"Ordinary" patterns generally do not scale, I think, but this could depend on how they were defined. One can design some with `patterns.meta` which should.

Diaa

@marmot, re: [your answer](#a1827),  I have another question if you don't mind:  
  
why the bricks pattern here doesn't scale down?  I mean the bricks should be scaled not zoomed in  
  
```  
  \documentclass{article}
\usepackage{tikz}
\usepackage{adjustbox}
\usepackage[american, siunitx , RPvoltages]{circuitikz}
\usetikzlibrary{3d,arrows.meta,bending,calc,decorations.markings,patterns,positioning,shapes.geometric}

\tikzset{pics/rotarrow/.style={code={\path (160:0.4) coordinate (tmpex);
			\begin{scope}[local bounding box=tmp,x={(tmpex)},
				canvas is xy plane at z=0]
				\clip (-0.41,-0.41) rectangle (0.41,0.41);
				\pgflowlevelsynccm
				\draw[thin,-{Stealth[bend]}] (-150:0.4) arc[start angle=-150,end
				angle=150,radius=0.4];
			\end{scope}
			\path (tmp.north) node [above] {\tikzpictext};
	}},pics/bar/.style={code={\draw[pic actions] (0,-#1) -- (0,#1);}},
	pics/bar/.default=0.5}

\begin{document}
	\begin{adjustbox}{width=0.25\linewidth}
	\begin{tikzpicture}[x=3em,y=3em, %<- this scales with the font size
		%scale = 0.5, transform shape,
		damper/.style={thick,
			decorate,
			decoration={markings,
				mark connection node=dmp,
				mark=at position 0.5 with
				{
					\node (dmp) [thick, inner sep=0pt,
					transform shape,
					minimum width=2em,
					minimum height=1.5em, draw=none,
					#1] {};
					\draw [thick] ([xshift=0.25em]dmp.north east) --
					(dmp.north west) -- (dmp.south west) --
					([xshift=0.25em]dmp.south east)
					([yshift=-0.25em]dmp.north east) --
					([yshift=0.25em]dmp.south east);
		}}},]
		
		\draw (0,2) coordinate[label=below:{$+$}] (TL)to[ R=$R_a$, o-] ++(2,0) 
		to[short,f=$i_a$] ++(0.1,0) 
		to[L,cute inductor, l=$L_a$,-.]  ++(2,0)  
		to[Telmech=M, name=M1] ++(0,-2) 
		to[short,-o] (0,0)	coordinate[label=above:{$-$}] (ML);
		\path (TL) -- node[midway]{$E_a$} (ML);
		%
		\path (M1) ++ (2,0) coordinate (N1);
		\draw[thick] (M1) -- pic[pic text={$T_m,\theta_m$}]{rotarrow} (N1) pic[thick]{bar};
		%
		\draw[thick] ([yshift=-4.5em]N1) coordinate (N2) pic[thick]{bar=0.90}
		-- ++ (-1,0) coordinate (N3) pic[thick]{bar=0.45};
		%	
		\draw[thick] ([yshift=-4em]N3) pic[thick]{bar=0.775} 
		-- pic[pic text={$\theta_L$}, pos=0.5 ]{rotarrow} % xscale=-1 to reflect
		++ (-1,0) node[anchor=top,cylinder, black, shape border rotate=0, draw, 
		minimum height=2, minimum width=1, aspect=0.4,
		cylinder uses custom fill, cylinder end fill = gray!20, 
		path picture={\draw($(c.before top)!0.5!(c.after top)$) -- (c.top);}] 
		(c) {$J_L$};
		%			
		\path (TL|-c) node[draw, rectangle, minimum height=5em, minimum width = 1.5em, 
		anchor=west,preaction = {fill=gray!10},pattern=bricks](bricks) {};
		%
		\draw [damper={label=below:{$D_L$}}] (c.west) -- (bricks);
		%
	\end{tikzpicture}
\end{adjustbox}
\end{document}
```
  ![blob](/image?hash=e1bfb8464df69889c5109b0cba38bc8b19a46f23378af5efa24f7c3cbcdbce97)

Diaa replying to marmot

My eyes can't feel the difference.

marmot replying to Diaa

Not really. `scale={3em/1cm},transform shape` works for the `circuitikz` nodes but not for everything, it seems.  
```  
\documentclass[tikz,border=3mm]{standalone}
\usepackage[american, siunitx , RPvoltages]{circuitikz}
\usetikzlibrary{3d,arrows.meta,bending,calc,decorations.markings,patterns,positioning,shapes.geometric}

\tikzset{pics/rotarrow/.style={code={\path (160:0.4) coordinate (tmpex);
 \begin{scope}[local bounding box=tmp,x={(tmpex)},
	canvas is xy plane at z=0]
  \clip (-0.41,-0.41) rectangle (0.41,0.41);
  \pgflowlevelsynccm
  \draw[thin,-{Stealth[bend]}] (-150:0.4) arc[start angle=-150,end
  angle=150,radius=0.4];
\end{scope}
\path (tmp.north) node [above,style/.expanded=\tikzpictextoptions] {\tikzpictext};
}},pics/bar/.style={code={\draw[pic actions] (0,-#1) -- (0,#1);}},
pics/bar/.default=0.5}

\begin{document}
\begin{tikzpicture}[%x=3em,y=3em, %<- this scales with the font size
	 	scale={3em/1cm},transform shape,
		damper/.style={thick,
				decorate,
				decoration={markings,
						mark connection node=dmp,
						mark=at position 0.5 with
							{
								\node (dmp) [thick, inner sep=0pt,
									transform shape,
									minimum width=2em,
									minimum height=1.5em, draw=none,
									#1] {};
								\draw [thick] ([xshift=0.25em]dmp.north east) --
								(dmp.north west) -- (dmp.south west) --
								([xshift=0.25em]dmp.south east)
 								([yshift=-0.25em]dmp.north east) --
								([yshift=0.25em]dmp.south east);
							}}},]

	\draw (0,2) coordinate[label=below:{$+$}] (TL)to[R=$R_a$,o-] ++(2,0) 
		to[short,f=$i_a$] ++(0.1,0) 
		to[L,cute inductor, l=$L_a$,-.]  ++(2,0)  
		to[Telmech=M, name=M1] ++(0,-2) 
		to[short,-o] (0,0)	coordinate[label=above:{$+$}] (ML);
	\path (TL) -- node[midway]{$E_a$} (ML);
	%
	\path (M1) ++ (2,0) coordinate (N1);
	\draw[thick] (M1) -- pic[pic text={$T_m,\theta_m$}]{rotarrow} (N1) pic[thick]{bar};
	%
	\draw[thick] ([yshift=-4.5em]N1) coordinate (N2) pic[thick]{bar=0.75}
		-- ++ (-1,0) coordinate (N3) pic[thick]{bar};
	%	
	\draw[thick] ([yshift=-3.5em]N3) pic[thick]{bar=0.75} 
	 -- pic[xscale=-1,pic text={$\theta_L$},pic text options={xscale=-1}, pos=0.5 ]{rotarrow} 
	 	++ (-1,0) node[anchor=top,cylinder, black, shape border rotate=0, draw, 
			minimum height=2, minimum width=1, aspect=0.4,
			cylinder uses custom fill, cylinder end fill = gray!20, 
			path picture={\draw($(c.before top)!0.5!(c.after top)$) -- (c.top);}] 
			(c) {$J_L$};
    %			
	\path (TL|-c) node[draw, rectangle, minimum height=5em, minimum width = 1.5em, 
		anchor=west,preaction = {fill=gray!10},pattern=bricks](bricks) {};
	%
	\draw [damper={label={[scale=-1]below:{$D_L$}}}] (c.west) -- (bricks);
	%
\end{tikzpicture}

\Large
\begin{tikzpicture}[%x=3em,y=3em, %<- this scales with the font size
		scale={3em/1cm},transform shape,
		damper/.style={thick,
				decorate,
				decoration={markings,
						mark connection node=dmp,
						mark=at position 0.5 with
							{
								\node (dmp) [thick, inner sep=0pt,
									transform shape,
									minimum width=2em,
									minimum height=1.5em, draw=none,
									#1] {};
								\draw [thick] ([xshift=0.25em]dmp.north east) --
								(dmp.north west) -- (dmp.south west) --
								([xshift=0.25em]dmp.south east)
 								([yshift=-0.25em]dmp.north east) --
								([yshift=0.25em]dmp.south east);
							}}},]

	\draw (0,2) coordinate[label=below:{$+$}] (TL)to[R=$R_a$,o-] ++(2,0) 
		to[short,f=$i_a$] ++(0.1,0) 
		to[L,cute inductor, l=$L_a$,-.]  ++(2,0)  
		to[Telmech=M, name=M1] ++(0,-2) 
		to[short,-o] (0,0)	coordinate[label=above:{$+$}] (ML);
	\path (TL) -- node[midway]{$E_a$} (ML);
	%
	\path (M1) ++ (2,0) coordinate (N1);
	\draw[thick] (M1) -- pic[pic text={$T_m,\theta_m$}]{rotarrow} (N1) pic[thick]{bar};
	%
	\draw[thick] ([yshift=-4.5em]N1) coordinate (N2) pic[thick]{bar=0.75}
		-- ++ (-1,0) coordinate (N3) pic[thick]{bar};
	%	
	\draw[thick] ([yshift=-3.5em]N3) pic[thick]{bar=0.75} 
	 -- pic[xscale=-1, pic text={$\theta_L$},pic text options={xscale=-1}, pos=0.5 ]{rotarrow} 
	 	++ (-1,0) node[anchor=top,cylinder, black, shape border rotate=0, draw, 
			minimum height=2, minimum width=1, aspect=0.4,
			cylinder uses custom fill, cylinder end fill = gray!20, 
			path picture={\draw($(c.before top)!0.5!(c.after top)$) -- (c.top);}] 
			(c) {$J_L$};
    %			
	\path (TL|-c) node[draw, rectangle, minimum height=5em, minimum width = 1.5em, 
		anchor=west,preaction = {fill=gray!10},pattern=bricks](bricks) {};
	%
	\draw [damper={label={[scale=-1]below:{$D_L$}}}] (c.west) -- (bricks);
	%
\end{tikzpicture}

\end{document}  
```

Diaa

@marmot, re: [your answer](#a1827),  In case you have any idea, do you know how to make the line thickness of the resistor and inductance the same as that of connecting wire?

marmot replying to Diaa

Yes, good point. Tried to fix it.

Diaa

@marmot, re: [your answer](#a1827), many thanks for your beautiful answer. I am currently away from PC but there is some minor visual tweak: the gears should be apart from each other a bit to indicate they are meshing gears not a belt around pulleys as I have in my question image.

1 Answer