1. Programmable Logic Controllers
Programmable Logic Controllers
Dr.Anucha Saengrung
October 11st ,2011

2. Today Outline Course Syllabus History of PLC class History of PLCs
Advantages of PLCs
Example of PLC Applications
How does PLC work?
S7 Family

3. Big Picture of the Whole PLC Course
Course Syllabus
Big Picture of the Whole PLC Course
Hardware
PLC Operations
AIs, AOs, PID Control
STEP7, SCL, GRAPHS
PROFIBUS

4. History of PLCs In 1968, engineers at Hydramatic division of General
Motor Corporations invented the first PLC.
- Use program to control the machine
- More Efficient, Smaller than the existing controller
- Easier to maintenance, lower cost
- Cheaper when compared to control by using relays
In 1970, using microprocessor in PLC
In 1975, using computer technology both hardware
and software with PLCs
In1993 IEC (International Electro-technical Commission)
specified the standards of PLC system, PLC languages,
data communications, etc.

5. History of PLCs At present, PLCs have higher performances
- Faster CPU, Higher memory
- Multi-processor
- Using remote I/Os
- Control using Intelligent Module
- Communicate via Ethernet Protocol, Profibus, ASI-bus
- etc.

6. Advantages of PLCs

7. Advantages of PLCs

8. Advantages of PLCs PLC Relays/Magnetic Contactors Cost Lower Higher
Size
Compact
Bigger Size
Speed
Fast
Slower
Tolerance to noise
Good
Excellent
Installation
Easy
Take more time for design and installation
Ability to control complex tasks
yes
Difficult to do
Ability to change the control sequences
Take time and efforts
Maintenance and trouble shooting when there is a problem
Maintenance is rarely required. Easy for trouble shooting.
Have to maintenance the coils and contacts. Hard to trouble shooting

9. Examples of PLC applications
Automotive Industry

10. Examples of PLC applications
Airports

11. PLANT PLC How does PLC work? I CPU Sensors - Switches Actuators
Inputs
Outputs
CPU
DIs, AIs
DOs, AOs
Sensors
- Switches
Transducers
Photocells
Actuators
- Valves
- Inverter
- Heater
- Motor
PLANT

12. S7 Family
S7-200
S7-300*
S7-400

13. PLCs in the market PLCs Europe SIEMENS ABB Honeywell Schneider
National Instrument …
Asia
OMRON
Mitsubishi
Yokokawa