New life for process control trainers in a microcontroller course

To improve student enthusiasm and demonstrate the power of embedded control, laboratory process control trainers were adapted and repurposed for use in an introductory microcontroller course. While some students are able to extrapolate the ideas conveyed by making an LED flash using assembly code, other students need to see their code doing something more powerful and realistic. Control system training rigs are common in engineering and technology laboratories. These trainers, from manufacturers such as Feedback®, typically have some type of "plant" that is the controllable center of the system. The parameters of the plant are then measureable via several types of process sensors. To complete the control loop, a programmable or otherwise adjustable control unit is provided to be used to demonstrate various closed-loop control techniques such as PID control. The system used here is the Feedback Basic Process Rig model 38-100. This system is comprised of a plumbing network in which the water level in a tank is regulated by controlling the flow of water into and out of the tank using solenoid and/or servo valves. Tank level and system flow rate sensors are used as inputs to the control unit. For the microcontroller course, the manufacturer's control unit was disconnected from the system and replaced with a microcontroller trainer board and a simple, custom interface box to make the appropriate interconnections. The students designed their own assembly code to read the system sensors and control the water level to a variable, user-determined set point. The required code components were developed throughout the semester as each peripheral of the microcontroller was discussed. The process control served as a culminating project for the course. This paper presents the system hardware and example student software. Course curriculum is also presented and discussed.