\documentclass[a4paper]{scrartcl}

\usepackage{tikz}
\usepackage[european resistor]{circuitikz}
\usepackage{siunitx}

\begin{document}

\begin{figure}
  \begin{circuitikz}
    % Raspberry Pi
    \draw (0.5, -0.5) rectangle (3, 3.5);
    \node at (1.5, 3) {\textbf{RPi}};

    \draw (3.5, 2) to [short] (2.5, 2) node [left] {GND};
    \draw (3.5, 0) to [short] (2.5, 0) node [left] {GPIO18};

    % Bread Board 1
    \draw (4, -0.5) rectangle (7.5, 3.5);
    \node at (5, 3) {\textbf{BB1}};

    \draw (3.5, 2) to [short] (4.5, 2) node [circ] {}
      to [short] (5.5, 2) node [circ] {}
      to [short] (8, 2);

    \draw (3.5, 0) to [short] (4.5, 0) node [circ] {}
      to [short] (5.5, 0) node [circ] {}
      to [R, l=$R_2$] (7.5, 0)
      to [short] (8, 0);

    \draw (4.5, 2) to [push button] (4.5, 0);
    \draw (5.5, 2) to [R, l=$R_1$] (5.5, 0);

    % Bread Board 2
    \draw (8.5, -3.5) rectangle (11.5, 3.5);
    \node at (10, 3) {\textbf{BB2}};

    \draw (8, 2) to [short] (9, 2) node [circ] {}
      to [short] (12, 2);

    \draw (9, 1) node [circ] {} to [empty led] (11, 1) node [circ] {}
      to [short] (12, 1);

    \draw (8, 0) to [short] (9.5, 0)
      to [empty led] (11.5, 0)
      to [short] (12, 0);

    \draw (9, -1) node [circ] {} to [R, l=$R_3$] (11, -1)
      to [short] (12, -1);

    \draw (10, -2) to [short] (12, -2);
    \draw (11, -3) to [short] (12, -3);

    \draw (9, 4) to [short] (9, -1)
      to [R, l=$R_4$] (9, -3)
      to [short] (9, -4);

    \draw (10, -2) to [short] (10, -4);

    \draw (11, 4) to [short] (11, 1);
    \draw (11, -3) to [short] (11, -4);

    % Door
    \draw (8.5, 4.5) rectangle (11.5, 6.5);
    \node at (9.5, 6) {\textbf{Door}};

    \draw (9, 5) to [empty led] (11, 5);

    \draw (9, 5) to [short] (9, 4);

    \draw (11, 5) to [short] (11, 4);

    % ADMN
    \draw (12.5, -3.5) rectangle (15, 3.5);
    \node at (13.5, 3) {\textbf{Arduino}};

    \draw (12, 2) to [short] (13, 2) node [right] {GND};
    \draw (12, 1) to [short] (13, 1) node [right] {D12};
    \draw (12, 0) to [short] (13, 0) node [right] {D10};
    \draw (12, -1) to [short] (13, -1) node [right] {A0};
    \draw (12, -2) to [short] (13, -2) node [right] {\SI{5}{\volt}};
    \draw (12, -3) to [short] (13, -3) node [right] {D13};

    % Sensor
    \draw (8.5, -4.5) rectangle (11.5, -7);
    \node at (9.5, -6.5) {\textbf{Sensor}};


    \draw (9, -4) to [short] (9, -5) node [rotate=90, left] {black};
    \draw (10, -4) to [short] (10, -5) node [rotate=90, left] {blue};
    \draw (11, -4) to [short] (11, -5) node [rotate=90, left] {red};

  \end{circuitikz}
  \caption{
    $R_1 = \SI{33}{\kilo\ohm} \pm \SI{2}{\percent}$,
    $R_2 = \SI{28}{\kilo\ohm} \pm \SI{2}{\percent}$,
    $R_3 = \SI{68}{\kilo\ohm} \pm \SI{1}{\percent}$,
    $R_4 = \SI{200}{\ohm} \pm \SI{1}{\percent}$,
  }
\end{figure}


\end{document}

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