INTRODUCTION TOINTRODUCTION TOFBD - Function Block Diagram byFBD - Function Block Diagram by

( LOGO )( LOGO )

Revision 2

Program Representation - FBDProgram Representation - FBDProgram Representation - FBDProgram Representation - FBD

» The graphical representation of a control task using symbols to DIN 40700 and DIN 19239

» Inputs are arranged on the left side while outputs on the right

FBD - Function Block Diagram

&I 0.0

I 0.1Q 4.0

FBDFBDFBDFBDOPERAND + OPERATION

OPERATION + OPERAND

= Q 4.0

Operation And OperandOperation And OperandOperation And OperandOperation And Operand

&I 0.0

M 80.0

Program ExecutionProgram ExecutionProgram ExecutionProgram Execution

PLC Scan Function:PLC Scan Function:

» Read the status of all inputs and outputs

» Examine the application program instructions

» Execute the control program

The Operand Areas :The Operand Areas :The Operand Areas :The Operand Areas :

» I (Input)Interface from the process to the programmable controller

» Q (Output)Interface from programmable controller to the process

» M (Memory/Flag)Memory for intermediate results of binary operations

Hardwire and PLC Wiring DiagramsHardwire and PLC Wiring DiagramsHardwire and PLC Wiring DiagramsHardwire and PLC Wiring Diagrams

How Does a Programmable Controller Work?How Does a Programmable Controller Work?How Does a Programmable Controller Work?How Does a Programmable Controller Work?

PowerSupply

ProgramMemory

ProcessorInput modules

Output modules

24 VDC

GND

Sensors

Actuators / Annunciators

Steps of Operation Steps of Operation Steps of Operation Steps of Operation

» The sensors are connected to the INPUT MODULES

» The processor in the CPU MODULE executes the program and scans the individual input for presence or absence of voltage

» Depending on the state of the inputs, the processor directs the OUTPUT MODULES to switch voltages

» The ACTUATORS or ANNUNCIATORS are switched “ON” or “OFF” according to the voltage states