1. UNICOS: UNified Industrial COntrol System CPC (Continuous Process Control) Basic course SESSION 3: PLC basics
UCPC 6 UNICOS-Continuous Process Control
CERN EN/ICE group

2. Overview

3. Overview Programmable Logic Controller
Designed for industrial processes.
Works under severe conditions.
Real time system.
Handles sensors and actuators (I/O).

4. Functions Process control Collects inputs (digital, analog)
Runs the process control
Basic logic functions
Complex algorithms (PID…)
Safety functions
Produces actions (outputs)
Provides data to the supervision layer

5. Features Reliable. Used for safety systems.
Robust. Resistant to electrical noise, vibration, impact, dust, heat.
Extensive range of inputs/outputs.
Extensive range of functionalities.
Long term support.
Long life, around 30 years.

6. Hardware overview Acquisition Supervisory Control And Data SCADA
ETHERNET TCP/IP
PLC
INDUSTRIAL FIELDBUS
DIRECT WIRING
REMOTE I/O
SENSORS/ACTUATORS

7. Device which converts the signal from one form to another. Sensors
Sensors - Actuators
Device which converts the signal from one form to another.
Sensors
Analog: Temperature, pressure, humidity, level, flow, weight…
Digital: Level, pushbutton (emergency stop), position switch, photoelectric sensor…
Actuators
Analog: valve, pump, heater, power supply…
Digital: Signaling column, contactor, electro valve, switch, OnOff pump…

8. Hardware Overview Supervisory Control And Data Acquisition SCADA
ETHERNET TCP/IP
PLC
INDUSTRIAL FIELDBUS
DIRECT WIRING
REMOTE I/O
SENSORS/ACTUATORS

9. Periphery Stations Communication modules I/O Modules.
Convert physical value into numeric value and vice versa.
Function modules.

10. I/O Modules Analog Digital 16-bit signed from -32768 to 32767.
Inputs: Resistance, Current, Voltage, thermocouple…
Outputs: Current, voltage.
Digital
1-bit
Inputs: 120v-230v AC, 24v DC
Outputs: Relay, 120v-230v AC, 24v-48v-125v DC.

11. Function Modules PID control Flow Camera controllers
Numerical controllers
Counters
Positioning

12. Communication modules
Ethernet
Profibus
CAN
Point to Point
Serial RS 232, RS 485
AS-Interface
Modbus…

13. Hardware Overview Supervisory Control And Data Acquisition SCADA
ETHERNET TCP/IP
PLC
INDUSTRIAL FIELDBUS
DIRECT WIRING
REMOTE I/O
SENSORS/ACTUATORS

14. Fieldbus- Overview Industrial Network System
Provides the PLC with I/Os
Time deterministic.
Saves cabling costs
Sensitive to electromagnetic noise.
Specific installation rules.
Several different (incompatible) fieldbus standards.

15. Fielbus Standards Profibus WorldFip CAN. CANOpen. CANBus ProfinetIO
Industry leader. 14 million nodes.
WorldFip
Robust (radiation resistant)
CAN. CANOpen. CANBus
Low cost
Easy to implement
Used for ELMB at CERN
ProfinetIO
Interbus integrated (Phoenix Contact).
Ethernet based fieldbus 15

16. Profibus PROFIBUS Token ring PC PLC Active nodes. Master
Passive nodes. Slaves.
PLC PC
Token ring 16

17. Hardware Overview Supervisory Control And Data Acquisition SCADA
ETHERNET TCP/IP
PLC
INDUSTRIAL FIELDBUS
DIRECT WIRING
REMOTE I/O
SENSORS/ACTUATORS

18. Siemens S7-200
S7 200 (low range)
Compact
Low cost
Small systems

19. Siemens S7-300 S7 300 (medium range) Modular Wide range of IOs
Widely used
Limited memory
Limited range of fieldbuses

20. Siemens S7-400 S7 400 (high range) Redundant architecture Large memory
High performance

21. Overview S7 1200 (high range) S7 1500 (high range) S7200 replacement
New architecture
TIA Portal
S (high range)
New architecture
Not redundant architecture (yet)
Larger memory
Higher performance
TIA Portal

22. Process cycle Process Cycle Cycle time 5-500 ms 22 Read inputs
Copy inputs to Input Process Image
Execute user program
Copy Output process Image to outputs
Write outputs
Comm
tasks
Process Cycle
Cycle time
5-500 ms
Internal mechanism of a PLC
simple. (more or less like a single task processor)
Not very fast from 4 to few 100 msec
NO DATA acquisition from PLC
No protection in the memory management
the OS will not decide for you.
The designer has to analyze all cases
like div by zero, funny values 22

23. Programming Languages
Traditional ladder logic is an easy-to-use graphical programming language that implements relay-equivalent symbol. Intuitive. Limited functionalities.
Language close to old cabling used by electrician. 23

24. Programming Languages
STL: Statement List / Instruction List - Fastest possible logic execution. Low level language (similar to assembly language)
Language close to old cabling used by electrician. 24

25. Programming Languages
FBD : Function Block Diagram
Language close to old cabling used by electrician.

26. Programming Languages
ST: Structured Text - Equations, table manipulation, complex algorithms (If/Then)
Language close to old cabling used by electrician.

27. Programming Languages
SFC : Sequential Function Chart -A graphical method of representing a sequential control system (stepper).
Language close to old cabling used by electrician.

28. Hardware Overview Supervisory Control And Data Acquisition SCADA
ETHERNET TCP/IP
PLC
INDUSTRIAL FIELDBUS
DIRECT WIRING
REMOTE I/O
SENSORS/ACTUATORS

29. Scada communication Ehternet TCP IP. Big amount of data transfer.
Non deterministic.
Big data transfer rates.
S7 Driver on TCP IP. Siemens.
OPC.