Control software for PID Test Rig

Sketch to control the PID test/learning rig. The hardware system for this code is described in the Arduino++ blog

Hardware requirements

• Arduino Uno/Nano/Mini/etc
• 2 line LCD module
• Rotary encoder with built in selection switch
• SR-04 Ultrasonic sensor

Function

This sketch controls a fan blowing into a vertical acrylic tube designed to
contain a floating ping pong ball. The control algorithm is supposed to
levitate the ball at a set height from the bottom of the tube.

• Distance using a SR-04 ultrasonic sensor located at the open end of the tube.
• The fan at the other end of the tube is controlled with a PWM signal into a
  L293D motor controller.
• A 2 line LCD display module and a rotary encoder are used to change the PID constants
  while tuning the loop. The LCD is connecteed with a Shift Register one-wire backpack;
  other types of LCD will requires changes to the class initialisation parameters
  to suit that hardware type.
• PID parameters can be saved to EEPROM and are reloaded at startup.
• Data can be logged to the Serial Monitor, Serial Plotter or PLX-DAQ for
  Microsoft Excel, by menu selection.