1. Discrete-state Process Control
Lecture 1
Discrete-state Process Control

2. Learning Outcome
Identify a discrete-state process control system and characterize it.
Design a simple relay-based discrete-state control system and document it using the proper circuit diagram.
Appreciate Programmable Logic Controllers as universal discrete-state process controllers in industrial applications

3. Textbook reading Page 387 – 396 Page 403 – 405 Section 8.4

4. Process Control
Controller
Set Point
Feedback
Output

8. What is Discrete-State Control?
not continuous control
on / off control
can be sequential control
More advances
timer / counter

9. Discrete Control The controller only provide ON / OFF control
Discrete Input – ON / OFF state such as push button, switch, floating switch, proximity switch, optical switch, etc.
Controller – Switch, Relay, Contactor

10. What is the different between Relay and contactor?
operates as the heart of the relay ladder control
operates at low voltage and low current, e.g. 12V and 24V d.c.
1P1T to 4P8T
Contactor
operates at power voltage, e.g. 220V / 380V
Contacts carry the load current such as motor current
With auxiliary contacts for the relay ladder (low voltage and low current)
Main contacts – 2P1T to 4P1T

11. What is a relay controller?
What is an electronic controller?
What is a PLC?

12. Activity
Design a Star-Delta Starter for a 3-phase 380V 10kW induction motor
Draw the power circuit and control circuit separately