The requirements for the final device are grouped to the three categories. Necessary requirements are bound to be met at any cost. Some of the high importance requirements can be skipped or slightly modified, if unreasonable obstacles are found. However, they are all assumed to be completed for well being of the project. Optional requirements will be completed only if possible, given the resources will allow it.
\textbf{Necessary:}
\begin{itemize}
\item Build a \gls{pcb} holding and interconnecting required components
\item Measure current at given voltage used by the measured appliance by any means
\item Provide a way to present the measurements by a quantity of power consumed
\item Make possible to measure more than one appliance at a given time
\item Make sure the device is compatible with European powerline grid system as well as with the European mains plug connector
\end{itemize}
\textbf{High importance:}
\begin{itemize}
\item Store the measured data for further analysis
\item Split the device to the server (separate GL-inet router running a web-server, data processing and data storage) and to measurement nodes (electronics powered by an ESP8266 wi-fi module) to create a unique, replicable and efficient solution
\item If reasonably accurate, use the inbuilt \gls{adc} of the ESP8266 for the voltage measurement in combination with a linear transformer (the transformer also powers the entire node)
\item Use hall-effect sensor for a current measurement
\item If possible, prevent the use of the external \gls{adc} as well as the use of the additional microcontroller to keep the cost down (if needed, use the microcontroller of the 8-bit AVR family produced by Atmel)
\item Provide suitable enclosures for an aesthetical effect of a finished product as well as a protection against the electrical shock
\item Provide a way to switch off/on the appliance under measurement by the user remotely
\item Make the presented measurements available as an usage graphs via web-server
\item Configure the server as a repeater to provide more better signal for the nodes
\item Measure the power factor by the simplest possible means
\item Try to provide as much of the security measurements on all layers as possible
\item Take care designing a device from a perspective of a thermal design
\end{itemize}
\textbf{Optional:}
\begin{itemize}
\item Measure the power factor with non-sinusoidal waveforms
\item Store the measured data on an external USB flash disk connected to GL-inet board in a form of SQLite database
\item Make the web-server accessible remotely via \gls{ddsn} service
\item Include advanced configuration options (\gls{pwm} for lighting appliances or or periodic turn on/off function)
\item Provide some simple native application for an Android platform, apart from web-server
\item Make the server automatically discover all nodes and configure them
\item Include one or more LED to indicate status and/or activity to the observing user
\end{itemize}
%Text záverečnej práce obsahuje kapitolu, v~rámci ktorej autor uvedie
%analýzu riešených problémov. Táto kapitola môže byť v~prípade
In the case of resistive (Ohmic, or linear) loads, Joule's law can be combined with Ohm's law (V = I·R) to produce alternative expressions for the amount of power that is dissipated:
$$P = IV = I^2R =\frac{V^2}R$$
where R is the electrical resistance.
\subsubsection{In alternating current (AC) circuits}
Peter Babič
9 years ago