Cascade switching allows the Arduino, with a limit of 20 mA output, to control solenoid valves that need 0.5A or more to actuate.

• Lecture slides PDF or PowerPoint on cascade switching.

The salinity control algorithm uses on/off control with a dead-end determined by measurements of system variability. The measurements are described in the next section. The following slides give a high level overview of why a deadband is used, and how the response time of the system also needs to be taken into account.

• Lecture slides PDF or PowerPoint on UCL, LCL and dead time.
• Study document for review of salinity control concepts and system behavior.

• Detailed notes and lab instructions on preparation for salinity control, summary
• fishtank_response_time.ino Arduino code for capturing data to measure response time of the fish tank.
• waiting_for_deadtime.ino Skeleton code for implementing deadtime in salinity control.

• Notes on using mass balances to compute the required correction when salinity is disturbed from the set point

• Solution to in-class problem on adding mass to correct the salinity in the fish tank
• Screencast on problem on correcting the salinity of the fish tank (21:15)