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Control technologies

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Control Technologies (3.2)

Information Technology 9626

Actuators, Feedback Loops, and Real-time Control Systems

Interactive Revision Notes with Self-Testing

What is Control Technology?
Feedback Loops and Real-time Processing
Sensors in Control Systems
Actuators and Types
Uses of Control Systems
Smart Homes and IoT
Advantages and Disadvantages
Summary and Review

1. What is Control Technology?

Learning Objectives:

Understand the purpose and function of control systems
Know the difference between monitoring and control systems
Understand how microprocessors control physical variables
Learn about real-time processing in control

Definition of Control System

Control System: A system that uses microprocessors or computers to control certain physical variables. The computer maintains physical conditions at the same level or controls devices to change variables. Physical variables that can be controlled include temperature, pressure, humidity, light, and moisture.

Key Difference: Monitoring vs Control

Monitoring Systems:

Only RECORD data
People view trends and patterns
No action is taken automatically
Example: Weather station records temperature for analysis

Control Systems:

Take ACTION based on sensor readings
Make decisions and respond automatically
Output affects the input (feedback loop)
Example: Heating system turns on/off to maintain temperature

The Feedback Loop Concept

CRITICAL CONCEPT: In control systems, the output affects the input. This creates a feedback loop.

Central Heating System Example

Process:

Input: Temperature sensor detects room temperature
Processing: Computer compares to desired temperature (pre-set)
Output: Computer signals heater to turn ON
Feedback Effect: Heater being ON causes room temperature to RISE
New Input: Temperature sensor now reads higher temperature
Loop Continues: When temperature reaches pre-set, heater turns OFF

Key Point: The output (heater on/off) directly affects the input (temperature reading). This is why it's called a feedback loop.

Real-time Processing

Real-time Processing: Data is processed immediately, and results/actions are produced without delay. Control systems use real-time processing because they must respond instantly to sensor inputs. Delays could be dangerous or ineffective.

Why Real-time is Essential:

Safety—delays could cause accidents (traffic lights, aircraft control)
Effectiveness—slow response means poor control (temperature drifts)
Continuous process—feedback loops run constantly while system is on

Quick Question 1

Why is a control system considered to have a "feedback loop" while a monitoring system does not?

2. Feedback Loops and Real-time Processing

The Control Loop Process

Complete Control Cycle:

User enters desired value (pre-set) using keypad/touchscreen
Computer stores this pre-set value in memory
Sensor continuously measures current value

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Also in the full note

3. Sensors in Control Systems
4. Actuators and Types
5. Uses of Control Systems
6. Smart Homes and IoT
7. Advantages and Disadvantages of Control Technology
8. Summary and Review
Control Technologies: Complete Overview
Master These Control Technology Concepts Checklist

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