PLC LADDER SIMULATOR

Ladder diagram online simulator

Draw trapezoidal diagrams in the browser, bind variables, click to run, and view results. No need to install software or buy a PLC. It adheres to the standard IEC 61131-3 instruction set, mirroring the behavior of real PLCs. Ideal for teaching demonstrations, algorithm verification, and on-the-job training.

Start drawing the trapezoidal diagram Instructions for Use
Ladder Editor
Start Stop Motor Motor TON IN Q PT ET TON.Q Valve
EDITOR

Ladder diagram editor

Drag components from the left component library, double-click to edit the variable name, and click the run button to start the simulation. It supports parallel branches, 6 types of coils, 4 types of contacts, and over 30 IEC standard function blocks.

Scanning cycle:
Operating status: stopped
Number of scans: 0
component library
Contact points
Normally open NO
Normally closed (NC)
Rising edge P
Falling edge N
Coils
Coil ( )
Negation ( / )
Set (S)
Reset (R)
Rising edge (P)
Falling edge (N)
Timers
TON
power-on delay
TOF
Power-off delay
TP
pulse
Counter Counters
CTU
Incremental counting
CTD
Countdown
CTUD
Bidirectional counting
Arithmetic
ADD
addition
SUB
subtraction
MUL
Multiplication
DIV
division
MOD
modulo
Compare and Compare
GT
greater than
LT
less than
GE
greater than or equal to
LE
less than or equal to
EQ
equal to
NE
not equal to
Logic (logic)
AND
AND
OR
OR
XOR
XOR
NOT
NOT
Data Data
MOVE
assignment
SEL
Choice
MUX
Multiple-channel selection
LIM
amplitude limiting
Edge Edge
R_TRIG
rising edge
F_TRIG
falling edge
Variable Table
NameTypeAddressValueOperation
DOCS

Instructions for Use

Basic Operations Drag components from the component library on the left to the canvas. Double-click a component to modify its variable name. After selecting a component, you can click it to delete or modify its type. The variable table on the right manages all variables. Multiple contacts within the same cascade are connected in series, and parallel branches are created through the right-click menu.
Simulation run Click "Run" to initiate the scanning cycle. The simulator repeatedly executes the following steps according to the set cycle: read input β†’ execute cascade logic from top to bottom β†’ write output. Variable values are displayed in real-time on the monitoring panel. Powered components are highlighted in green.
Supported components (IEC 61131-3) There are 4 types of contacts: NO, NC, rising edge P, and falling edge N. There are 6 types of coils: normal, inverting, set S, reset R, rising edge P, and falling edge N. There are over 30 function blocks: TON/TOF/TP/CTU/CTD/CTUD/ADD/SUB/MUL/DIV/MOD/GT/LT/GE/LE/EQ/NE/AND/OR/XOR/NOT/MOVE/SEL/MUX/LIMIT/R_TRIG/F_TRIG. These cover the commonly used instructions in the IEC 61131-3 standard ladder diagram.
SVG block source The SVG path data for all contacts and coils are sourced from the OpenPLC Editor open-source project (Autonomy-Logic/openplc-editor), ensuring complete consistency in viewBox, coordinates, and stroke width. The rendering method of functional blocks follows the BlockNodeVisual component of OpenPLC Editor.
The difference between it and a real PLC The logic execution is consistent with a real PLC - scanning from top to bottom line by line, with coils writing back to variables. The difference lies in the fact that the scanning cycle is as short as 10ms, and it does not support high-speed counting and motion control. It is suitable for logic verification and teaching.