diff --git a/docs/circuit/build_circuit_diagram.sh b/docs/circuit/build_circuit_diagram.sh
new file mode 100755
index 0000000..153f41e
--- /dev/null
+++ b/docs/circuit/build_circuit_diagram.sh
@@ -0,0 +1,6 @@
+#!/bin/sh
+
+trap 'rm -f circuit.aux circuit.log circuit.pdf' 0
+
+# create circuit.png
+pdflatex -shell-escape circuit
diff --git a/docs/circuit/circuit.md b/docs/circuit/circuit.md
new file mode 100644
index 0000000..b0c07c0
--- /dev/null
+++ b/docs/circuit/circuit.md
@@ -0,0 +1,59 @@
+# Space Status Circuit
+
+The status of Krautspace's door is captured, displayed and broadcast into the
+internet by an Arduino, a Raspberry Pi, and some circuitry. The following
+diagram shows a detailed representation of the circuit.
+
+The Arduino is (and should be only) responsible for the sensor read out and the
+local status display (traffic light).
+
+The Raspberry Pi is (and should be only) responsible for grabbing the status
+from the Arduino and broadcasting it to the internet.
+
+![Circuit diagram](circuit.png)
+
+## Sensor
+
+The locked-unlocked-state of the door is determined by a reed switch
+embedded in the strikeplate hole, that is triggered by a magnet glued to the
+lock's deadbolt.
+
+The switch is connected to the Arduino via two wires.
+
+## Arduino
+
+The system uses an Arduino Duemilanove. It monitors the state of the reed switch
+and controls three LEDs on the breadboard.
+
+The reed switch is connect to a 5V pin and pin D13. Note, that pin D13 also
+controls the on-board LED, so whenever the switch is in the closed state (DOES
+THIS CORRESPOND TO THE DOOR BEING IN THE CLOSED STATE?), the on-board LED is on.
+
+Three LEDs, green, yellow, and red, on a breadboard have their anodes connected
+to pins D10, D11, and D12 and their cathodes to GND.
+
+The Arduino gets its power via a USB cable from the Raspberry Pi. This gives
+them with a common ground. If this were not the case, the connection between
+their grounds via the breadboard, as it exists right now and is shown in the
+diagram, would be required.
+
+The logic of how the state of the reed switch is converted into the state of the
+LEDs is discussed in the documentation of the Arduino software.
+
+## Circuit
+
+The circuit uses 120Ω series resistors for the LEDs.
+
+The circuit also includes a voltage divider for the Raspberry Pi's connection
+to the anode of the green LED. The voltage is reduced from 5V to
+1.8kΩ/(1.8kΩ + 2.1kΩ) * 5V ~= 0.5 * 5V ~= 2.5V.
+
+## Raspberry Pi
+
+The system uses a Raspberry Pi Model 3.
+
+The Raspberry Pi grabs the state of the green LED from its anode on the
+breadboard. This is done via pin GPIO18.
+
+The logic of how this state is communicated to the internet is discussed in the
+documentation for the Raspberry Pi software.
diff --git a/docs/circuit/circuit.png b/docs/circuit/circuit.png
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index 0000000..9e7a5fb
Binary files /dev/null and b/docs/circuit/circuit.png differ
diff --git a/docs/circuit/circuit.tex b/docs/circuit/circuit.tex
new file mode 100644
index 0000000..19b14fe
--- /dev/null
+++ b/docs/circuit/circuit.tex
@@ -0,0 +1,94 @@
+\documentclass[border=10, convert={outfile=\jobname.png}]{standalone}
+
+\usepackage[european resistor]{circuitikz}
+\usetikzlibrary{fit, shapes.misc}
+\usepackage{siunitx}
+
+\begin{document}
+\begin{circuitikz}[]
+  % Raspberry Pi 3B
+  \draw (0.5, 3.5) rectangle (3, -2);
+  \node[right] at (1, 3) {\textbf{Raspi}};
+
+  \draw (3.5, 2) to [short] (2.5, 2) node [left] {GND};
+  \draw (3.5, 0) to [short] (2.5, 0) node [left] {GPIO18};
+
+  \draw (1.75, -1.5) node [above] {USB}
+    to [short] (1.75, -2.5);
+
+  % Bread Board
+  \draw (4, 3.5) rectangle (11.5, -4);
+  \node[right] at (4.5, 3) {\textbf{Breadboard}};
+
+  \draw (3.5, 2) to [short] (4.5, 2) node [circ] {}
+    to [short] (6.5, 2) node [circ] {}
+    to [short] (12, 2);
+
+  \draw (3.5, 0) to [short] (4.5, 0) node [circ] {}
+    to [R, l=$\SI{1.8}{\kilo\ohm}$] (6.5, 0)
+    to [short] (10.5, 0);
+
+  \draw (12, 1)
+    to [short] (10.5, 1)
+    to [R, l_=$\SI{120}{\ohm}$] (8.5, 1)
+    to [empty led, l_=Green] (6.5, 1) node [circ] {};
+
+  \draw (12, -1.5)
+    to [short] (10.5, -1.5)
+    to [R, l_=$\SI{120}{\ohm}$] (8.5, -1.5)
+    to [empty led, l_=Yellow] (6.5, -1.5) node [circ] {};
+
+  \draw (12, -3)
+    to [short] (10.5, -3)
+    to [R, l_=$\SI{120}{\ohm}$] (8.5, -3)
+    to [empty led, l_=Red] (6.5, -3) node [circ] {};
+
+  \draw (11, -3) to [short] (12, -3);
+
+  \draw (4.5, 2) to [R, l=$\SI{2.1}{\kilo\ohm}$] (4.5, 0);
+
+  \draw (6.5, 2) to [short] (6.5, -3);
+
+  \draw (10.5, 1) node [circ] {}
+    to [short] (10.5, 0);
+
+  % Arduino Duemilanove
+  \draw (12.5, 3.5) rectangle (16, -3.5);
+  \node[right] at (13, 3) {\textbf{Arduino}};
+
+  \draw (12, 2) to [short] (13, 2) node [right] {GND};
+  \draw (12, 1) to [short] (13, 1) node [right] {D10};
+  \draw (12, -1.5) to [short] (13, -1.5) node [right] {D11};
+  \draw (12, -3) to [short] (13, -3) node [right] {D12};
+
+  \draw (16.5, 2) to [short] (15.5, 2) node [left] {\SI{5}{\volt}};
+  \draw (16.5, 0) to [short] (15.5, 0) node [left] {D13};
+
+  \draw (15, -3) node [above] {USB}
+    to [short] (15, -4);
+
+  % Sensor
+  \draw (17, 3.5) rectangle (19.5, -0.5);
+  \node[right] at (17.5, 3) {\textbf{Sensor}};
+
+  \draw (16.5, 2) to [short] (18, 2);
+  \draw (16.5, 0) to [short] (18, 0);
+
+  \draw (18, 2) to [normal open switch, name=switch] (18, 0);
+  \node [rounded rectangle, line width=1pt, draw, fit=(switch), inner ysep=1pt, inner xsep=10, rotate=90] at (switch.center) {};
+
+  % USB cable
+
+  \draw (1.75, -2.5)
+    to [short] (1.75, -5)
+    to [short, l=Power for Arduino] (15, -5)
+    to [short] (15, -4);
+\end{circuitikz}
+
+\end{document}
+
+%%% Local Variables:
+%%% coding: utf-8
+%%% mode: latex
+%%% TeX-engine: xetex
+%%% End:
diff --git a/docs/hardware/.gitignore b/docs/hardware/.gitignore
deleted file mode 100644
index 8491230..0000000
--- a/docs/hardware/.gitignore
+++ /dev/null
@@ -1,3 +0,0 @@
-circuits.aux
-circuits.log
-circuits.pdf
diff --git a/docs/hardware/build_circuits.sh b/docs/hardware/build_circuits.sh
deleted file mode 100755
index f82d0ac..0000000
--- a/docs/hardware/build_circuits.sh
+++ /dev/null
@@ -1 +0,0 @@
-xelatex circuits.tex
diff --git a/docs/hardware/circuits.tex b/docs/hardware/circuits.tex
deleted file mode 100644
index 79f033c..0000000
--- a/docs/hardware/circuits.tex
+++ /dev/null
@@ -1,109 +0,0 @@
-\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}
-
-%%% Local Variables:
-%%% coding: utf-8
-%%% mode: latex
-%%% TeX-engine: xetex
-%%% End: