Engineering · Learn & build · PLC · version 1
PLC Simulator
Pick a PLC brand, load an industrial machine, and watch the ladder light up while the machine moves.
One program, seven brands. Choose Siemens, Allen-Bradley, Mitsubishi, Delta, Omron, Schneider or Inovance and the same machine is shown with that brand’s addresses, symbols and instructions. See every program as ladder, structured text, function blocks, instruction list and sequential chart. Press buttons, flip switches, load boxes and fill tanks in the virtual plant. Browse all 15 ready PLC projects with pictures and step-by-step notes. For writing your own program, use the PLC Program Builder.
This is a learning tool. It teaches the logic, not the exact keystrokes of each vendor’s software, and instruction names and addresses can differ between models and software versions. Always check the manual of your own PLC. It is not a safety PLC and must never be used to design safety functions.
A tough computer
A PLC (programmable logic controller) is a small industrial computer. It reads switches and sensors, runs your program and switches contactors, valves and lamps. It is built to survive heat, dust and noise on a factory floor.
The scan cycle
It repeats three jobs thousands of times a second: read all inputs, run the program from top to bottom, write all outputs. Watch the picture below.
24 V DC signals
Most inputs and outputs work at 24 V DC. Motors and heaters are switched through a contactor, never straight from the PLC output.
Ladder logic
Ladder looks like an electrician’s drawing. Contacts on the left are conditions, the coil on the right is the result. Green means power is flowing.
Five languages
The IEC 61131-3 standard defines ladder (LD), structured text (ST), function block diagram (FBD), instruction list (IL) and sequential function chart (SFC). Each PLC supports some of them.
Stop buttons are wired closed
A STOP button is wired normally closed (N.C.), so the input is ON in normal running. If a wire breaks the input goes OFF and the machine stops. That is the safe way to fail.
The PLC (click the RUN / STOP switch)
Every signal has a name and an address on the PLC you picked. Values update live. Green = ON. Timers show elapsed time and counters show the count.
| Name | Address () | Type | Value | What it is |
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Wiring and cautions
The same job is written differently on each PLC. Names and details can change with the model and software version, so check your manual.
For this project and the PLC you picked. The links open a search so you always see what is in stock today. Check the model, voltage and price before you order.
| # | Item | Buy / compare |
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How to use it
- Pick a PLC brand. The addresses, symbols and instructions change; the logic does not.
- Pick a project. The virtual machine appears with its buttons, lamps and process.
- Press buttons and flip switches on the machine. Watch the ladder: green wires carry power, grey wires do not.
- Use the language tabs to see the same program as structured text, function blocks, instruction list or a sequential chart.
- The RUN / STOP switch on the PLC picture works like the real one. In STOP all outputs turn off.
The five languages
- LD Ladder: contacts and coils. Best for on / off machine logic and for electricians.
- ST Structured Text: written like a program with IF, CASE and assignments. Best for maths and sequences.
- FBD Function Block: boxes joined by lines, like a logic circuit. Common in process control.
- IL Instruction List: one short instruction per line, close to the machine. Older style, many brands have dropped it.
- SFC Sequential chart: numbered steps and the conditions to move on. Best for step-by-step machines.
What the simulator does and does not do
It runs one scan every 20 ms in your browser, with the same logic for every brand. It does not copy each vendor’s software, hardware limits, memory areas, scan time or error handling. Timer units, counter direction and some instruction names are shown per brand, but you must verify them against the manual before you program a real machine.
What is new
- v1 · 26 Oct 2026: seven PLC brands (Siemens, Allen-Bradley, Mitsubishi, Delta, Omron, Schneider and Inovance), ladder, ST, FBD, IL and SFC views, 15 industrial projects.