PLC and Ladder

Place a PLC from the symbol column and choose the model in its properties. The symbol shows the real terminal blocks, LEDs and status indicators of the device; LOGO! shows its display with the state of I and Q.

Models

Model	Supply	Inputs	Outputs	Addresses
Siemens LOGO! 8 230RCE	115–240 V AC/DC	I1–I8	Q1–Q4 relay	I1, Q1, M1
Siemens LOGO! 12/24RCE	12/24 V DC	I1–I8 (AI1–AI4)	Q1–Q4 relay	I1, Q1, M1, AI1
Siemens S7-200 CPU 222 / 224	24 V DC or 230 V AC	8 / 14 DI	6 / 10 DQ	I0.0, Q0.0, M0.0
Siemens S7-1200 CPU 1214C	230 V AC	14 DI, 2 AI	10 DQ relay	%I0.0, %Q0.0, %M0.0, %IW64
Schneider M221 TM221CE16R	230 V AC	9 DI	7 DQ relay	%I0.0, %Q0.0, %M0, %IW0.0
Generic PLC	configurable	configurable, AI	configurable, AQ	IEC style

Wiring

Wire the supply terminals, the input common (1M / L+ / M) and the inputs; outputs are relay contacts between the group common (1L, 2L) and the output terminal. Each input needs the right voltage (24 V DC for most models, 230 V AC for LOGO! 230RCE); wrong voltage is reported in simulation. LEDs light for active inputs and outputs.

The Ladder editor

Open it from the PLC properties (Ladder program…) or by double-clicking the PLC. Each PLC has its own floating, resizable window; several can be open at once. The left power rail is fixed; draw freely:

Choose an instruction from the groups in the window's left column and click to place it. Drag from a terminal to draw a wire; touching terminals connect.
Inputs: NO, NC, positive and negative edge contacts. Outputs: coil, negated coil, set, reset. Coils need no connection on the right.
Timers TON, TOF, TP; counters CTU, CTD, CTUD; comparisons =, ≠, >, ≥, <, ≤ with numbers, counter values, timer times or analog values; analog SCALE and UNSCALE.
Addresses are entered in the properties panel, in the spelling of the model; the panel offers the inputs and outputs that are wired, with the names of the connected devices.
Frames and free text document the program; multi-select, copy, paste and duplicate work as in the drawing.

Execution

The PLC runs a scan cycle: read inputs, execute the program top to bottom (power flows only left to right), write outputs. In simulation the live power flow is shown in red, conducting contacts and energised coils are highlighted and timer and counter values are displayed. Click STOP on the PLC to halt the program.

Printing

Each editor window has its own PDF button for the program alone. The project PDF prints the sheet as you see it: open editor windows are printed in place, without their toolbars.