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jaseg 2022-09-27 18:20:32 +02:00
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paper/safety-reset-paper.tex
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@ -838,6 +838,13 @@ without triggering them to reset.
to the smart meter in the middle through an adapter board. The top left contains a USB hub with debug interfaces to
the reset microcontroller. The cables on the bottom left are the debug USB cable and the \SI{3.5}{\milli\meter}
audio cable for the simulated mains voltage input.}
\Description{A photo of the safety reset prototype. Visible is a stand made from plywood to which a smart meter is
mounted in the middle. To one side of the smart meter a light switch and a socket are connected. To the other side,
an orange power cable exits towards the back of the stand. The smart meter is connected to a prototype circuit board
with colorful wires. The prototype circuit board is in turn connected to a microcontroller development board. The
development board is connected to a USB hub with both an SWD programming adapter and a USB to serial converter. A
usb cable from the USB hub as well as a 3.5 millimeter audio cable from the prototype circuit board are neatly
coiled up and hang down from the stand.}
\label{fig_proto_pic}
\end{figure}
@ -864,13 +871,18 @@ the meter's display after boot-up.
\centering
\includegraphics[width=0.45\textwidth]{prototype_schema}
\caption{The signal processing chain of our demonstrator.}
\Description{A photo of the safety reset prototype. Visible is a stand made from plywood to which a smart meter is
mounted in the middle. To one side of the smart meter a light switch and a socket are connected. To the other side,
an orange power cable exits towards the back of the stand. The smart meter is connected to a prototype circuit board
with colorful wires. The prototype circuit board is in turn connected to a microcontroller development board. The
development board is connected to a USB hub with both an SWD programming adapter and a USB to serial converter. A
usb cable from the USB hub as well as a 3.5 millimeter audio cable from the prototype circuit board are neatly
coiled up and hang down from the stand.}
\Description{A diagram showing the signal processing flow. The diagram shows a number of steps going from grid
voltage waveform to trigger decition. The diagram begins with the DMA-assisted ADC capture. At this point, the
signal is a clean analog sine wave. The next step is grid frequency estimation, after which the signal is a
noise-like ragged line. After grid frequency estimation follows DSSS demodulation, which itself is made up of three
steps. The first step of DSSS demodulation is convolution, which produces a small noise signal with a large peak
somewhere in the middle. The peak is roughly ten times the amplitude of the noise and has two prominent negative
sidelobes to the left and right. The following step, CWT peak contrast enhancement, clenas up this signal and
removes the side-lobes leaving only the positive peak sticking out of the background noise. The final step of DSSS
demodulation is maximum likelihood estimation, which produces a vector of n plus k discrete elements. After DSSS
demodulation, this vector is passed through Reed-Solomon error correction, which transforms it into a vector of now
only n discrete elements. This vector is then finally processed in the cryptographic trigger protocol, which
produces the final trigger decision.}
\label{fig_demo_sig_schema}
\end{figure}