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\subsubsection{The Sensor Array}  The sensor array has two functions: to detect how many candlelights are present and to test whether the candlelights that are present are flickering. Each candlelight is tested in a separate well with dedicated sensors for only that well. In other words, there is a separate collection of sensors for each candlelight.  Light from the candlelight is detected with a PBW34 yellow photodiode.\cite{VishaySemiconductors:2011} If a candlelight is present, and on, the light absorbed by the photodiode is converted to a current which in turn biases a TIP142 transistor.\cite{SharpMicroelectronics:2009} transistor.\cite{ONSemiconductor:2012}\cite{SharpMicroelectronics:2009}  The output from each transistor is combined in a CD4067 digital/analog 16-to-1 multiplexer, so that the PIC can select one signal at a time.\cite{TexasInstruments:2003} Only 9 channels are used. The output from the mux is passed through a LM358 Op-Amp to amplify the signal.\cite{FairchildSemiconductor:2010}  Presence is detected with the aid of superbright LEDs mounted beneath the candlelight wells, under the tray. There is one LED for each well. The LEDs are powered by 5V at 2A.