deletions | additions       diff --git a/Circuits.tex b/Circuits.tex  index a4c8c35..86fe71c 100644  --- a/Circuits.tex  +++ b/Circuits.tex 
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The primary problems were electrical interference between subsystems, and miswiring arising from the complexity and breadth of the electrical system. Interference was overcome by compartmentalizing the electrical system so that units operated independently of eachother, mitigating a cascading failure effect. Correctly connecting subsystems together was accomplished by careful labeling and organizing of wires.   \subsection{Solution}  The \textit{The  sensor array: 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. 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. 
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Greater light intensity corresponds with a higher output voltage. The intensity of light detected by the photodiode is a function of the intensity of the emitter, but also the distance from the sensor. The candlelights are closer to the photodiode than the presence illumination LEDs beneath the tray.   The sensor array consists of a circuit board containing the circuitry for the 9 yellow photodiodes, the 9 respective transistors for power amplification and the Op-amp. The mux for the yellow light signals is mounted next to the yellow sensor board, and they receive the same voltage and ground. The PIC also has a ground reference linked to the ground of the sensor board. The sensor board is powered by 5V at 2A. The light detecting circuit can be seen in figure # (!!!!!!)  Servo \textit{Servo  motors driver circuit: circuit:}  Driving servo motors is a simple operation. The 3 servos are operated at the same time, and in the same direction, so the voltage supplies, the grounds and the signals from the PIC are lumped together. The servos are powered with 5V at high current, #A, which is their maximum draw for maximum mechanical power. The signal wire for the 3 servos is connected to the signal hub to receive PWM from the PIC. A ground reference from the PIC is connected to the ground for the servos. The servo driver circuit can be seen in figure #. (!!!!!!!)  Stepper \textit{Stepper  motors driver circuit: circuit:}  Each of the two stepper motors has a ULC2003A IC transistor array to amplify the sequence signal from the PIC and provide the stepper coils with current. The input for the two ICs is joined because like the servo motors, both steppers operate at the same time, in the same direction, and therefore receive the same signal from the PIC simultaneously. The four inputs connect to the signal hub for communication with the PIC. A ground reference for the PIC is connected to the stepper driver board. The stepper driver board is powered by 5V at 2A. The four outputs from each IC connect to one bipolar stepper motor. Each bipolar stepper motor has two power leads connected to the same 5V that powers the driver board. The stepper driver circuit can be seen in figure #. (!!!!!!)  Signal hub: \textit{Signal hub:}  The signal hub consists of a circuit board with a dock to insert the bus cable from the PIC and signal wires soldered to the correct pins. The signal hub is merely an extension of the signal hub on the devbugger board. Figure # illustrates the purpose of each wire connected to the signal hub. Blank denotes unused.  Power \textit{Power  supply network: network:}  The device is powered by a (TYPE) ATX computer power supply, which provides the PIC with 12V at 1A, the servo motors with 5V at 22A (!), and 5V at 2A which powers everything else, including the IR sensor board, the yellow sensor board, the stepper motor driver board, and the steppers themselves. A separate power and ground wire is run to each subsystem, and the wires converge immediately before the power supply. The wires from the power supply carrying 5V at 2 and 22A respectively first pass through the emergency cut-off switch, allowing for the immediate halt of current flow to all components of the device except for the PIC and illumination LEDs. These components do not move, and are powered by extremely low current, therefore these remaining live wire does not pose a risk. A full outline of the circuitry of the device can be seen in figure #. (!!!!!)