Process Control Systems

Process Control

• Automated control of output by comparing its value to a desired value and sending the error signal back to control the input variable via a feedback loop
• Controllers: PLC, microcontroller, SCADA
• Controlled/Measuring Variable: output of process
• Manipulated Variable: input to process (depends on control signal from controller to actuator)
• Set Point: desired value of output variable

Transducers

• Devices that change energy from one form to another
• Subtypes:
  • Input Transducer (Sensor): converts physical phenomenon to electrical signal
  • Output Transducer (Actuator): converts electrical signal to physical phenomenon

Vibration/Shock Sensor

• Widely used in video games
• Works by changing output voltage from high to low when vibration occurs
• Output pin is connected to actuator through relay (for 220V actuators) or transistor switch or optocoupler (for lower voltage actuators)

Sound Sensor

• Consists of a microphone and comparator circuit
• Mic senses sound, converts it to digital signal, and compares amplitude to 2.5V
• Outputs 1 if sound signal amplitude is more than 2.5V, and 0 if less than 2.5V
• Also has analog output pin for estimating sound intensity

Passive Piezo Buzzer Module

• Converts electrical signals into tone
• Receives flow of signals with desired duration and frequency, producing sounds variant in duration and intensity
• Named piezo due to dependence on piezoelectricity

Rotary Encoder Module

• Senses direction of rotation, used in applications like rotary buttons in cars and MP3 players
• Has 2 pins (CLK and DT) that output different voltage levels depending on direction of rotation
• Sequence of pin outputs determines direction of rotation

Actuators and Microcontrollers

• Actuators: devices that perform actions, such as motors, light bulbs, LCD screens, speakers, and valves
• Microcontrollers: devices that control actuators, such as PIC, ARM, and AVR
• Factors to consider when picking a microcontroller