Arduino Sense is feeding back temperature and pressure from its on board sensors, plus fan speed using a photodiode and LED to count pulses. It is converting the values to a voltage and this is going to the analogue pins of the PLC. The PLC has push buttons to start, stop, Estop and reset in the digital inputs. The outputs represent engine on LED, engine on command (turn on fan), an LED to represent a starter motor, and a fault LED. Sequence shows the PLC during an autostart sequence, but starts at the third attempt, which then shows the autostart failing and locking off the program and turning on the fault indicator.

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