PLC programming languages include ladder diagram (LD), structured text (ST), sequential function chart (SFC), function block diagram (FBD), and instruction list (IL). Ladder diagram is the simplest form of PLC programming and represents relay logic using rungs and rails. Function block diagram uses blocks to represent program instructions that take inputs on the left and output values on the right. The document also discusses an example of ladder logic using two pushbuttons to control a lamp and describes function block diagrams as representing the relationship between input and output states.

1. PLC Programming
Languages

2. PLC Programming Languages
Ladder Diagram (LD)
Structured Text (ST)
Sequential Function
Chart (SFC)
Function Block
Diagram (FBD)
Instruction List (IL)

3. Ladder Diagram (LD)
 Ladder logic is the simplest from of PLC programming It is also known as
“Relay logic”.
 The Relay contacts used in relay controlled systems are represented using
ladder logic.we check example.
Ladder Logic
In the mentioned example, two
pushbuttons are used to control the same
lamp load. When any one of the switches
is closed, the lamp will glow.
The two horizontal lines are called rungs
and two vertical lines are called rails.
Every rung forms the electrical
connectivity between Positive rail (P) and
Negative rail (N). This allows the current
to flow between input and output devices.

4. Function Block Diagram
 Functional Block Diagram (FBD) is a simple and
graphical method to program multiple functions in
PLC.
 PLC Open has described using FBD in the
standard IEC 61131-3.
A function block is a program instruction unit that,
when executed, yields one or more output values.It
is represented by a block as shown fig.
It is represented as a rectangular block with inputs
entering on left and output lines leaving at the
right.
It gives a relation between the state of input and
output

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