PLC Simulator
Motor control PLC

Practise Motor Control PLC Ladder Logic in the Browser

Build and test the classic motor-control rungs — start/stop seal-in, forward/reverse interlock, jog, and star-delta — with no install. An honest learning simulator for the ladder logic, not a real motor or drive.

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Motor control PLC simulator — practice start/stop seal-in, forward/reverse interlock, jog, and star-delta motor control ladder logic in the browser with no install
A browser motor-control PLC simulator — practice the seal-in, interlock, jog, and star-delta rungs.

Why this page

Motor control is the first real PLC job you will do.

Almost every machine starts with a motor, and almost every motor is controlled by the same handful of ladder rungs. Learn the start/stop seal-in, forward/reverse interlock, jog, and star-delta patterns once and you can read most industrial control schematics. This page walks each rung and lets you rehearse the logic in the browser before you wire anything real.

The classic first rung

Start / stop seal-in

The three-wire start/stop rung is the foundation of motor control. A momentary Start push-button energises the motor contactor coil; a normally-open auxiliary contact of that coil is wired in parallel with Start so the rung seals in and stays on after you let go. A normally-closed Stop push-button in series drops it out.

Two details make it safe: the Stop button and the overload (OL) contact are both wired normally-closed. If a wire breaks, the rung opens and the motor stops — that is fail-safe behaviour, and it is the single most important habit in motor control.

Motor start stop PLC ladder logic seal-in rung: a Start contact, a normally-closed Stop push-button, a normally-closed overload contact, and a Motor contactor coil
The start/stop seal-in rung — fail-safe normally-closed Stop and overload in series with the Motor coil.
Motor start/stop seal-in PLC ladder rung — a momentary Start contact in parallel with a Motor hold contact, in series with a normally-closed Stop, latches the motor contactor coil on after Start is releasedA seal-in latch rung: a Start contact in parallel with a Hold contact, in series with a normally-closed Stop contact, driving an output coil.StartHold (seal)StopMotor
The seal-in (motor latch) animated: the Start press energises the coil, and the parallel Motor contact holds it sealed-in after release.

Want the deeper theory on the seal-in? Read seal-in rungs explained, then come back and build one here.

The interlock

Forward / reverse interlock

To run a motor both ways you build two seal-in rungs — one for Forward, one for Reverse — and then cross-interlock them. A normally-closed Reverse contact sits in the Forward rung, and a normally-closed Forward contact sits in the Reverse rung. The instant one contactor energises it opens the other rung, so the two contactors can never be on together. That is what prevents a phase-to-phase short across the motor terminals.

Forward reverse interlock PLC rung: the forward motor control rung with a Forward push-button, normally-closed Stop, and a normally-closed Reverse interlock contact blocking the forward contactor
Forward rung — a normally-closed Reverse contact interlocks it.
Forward reverse interlock PLC rung: the reverse motor control rung with a Reverse push-button, normally-closed Stop, and a normally-closed Forward interlock contact blocking the reverse contactor
Reverse rung — a normally-closed Forward contact interlocks it.
Forward reverse PLC timing diagram showing a forward run, a stop, then a reverse run where the forward and reverse contactor outputs never overlap because the interlock blocks both energising at once
Forward → off → reverse: the interlock guarantees the two contactor outputs never overlap.
Forward/reverse motor control PLC schematic — Start, Stop and direction push-buttons wire into PLC inputs, the controller solves the cross-interlocked ladder, and Forward and Reverse contactor coils switch three-phase power to the motorA 3-wire motor control circuit: Stop and Start pushbuttons, a contactor coil with a seal-in auxiliary contact and an overload contact, driving a motor.StopStartM (seal-in)OLMMmotor
How motor control maps end-to-end: push-buttons in, the PLC solves the interlocked logic, contactor coils out, motor switched by the contactors.

Inching the machine

Jog (inch) control

A jog rung is a seal-in rung with the seal removed. There is no parallel auxiliary contact, so the motor runs only while you hold the Jog button and stops the moment you release it. Jog is how you nudge a conveyor or spindle into position without latching it into a continuous run.

Motor jog inch PLC rung: pressing the Jog push-button energises the Motor contactor with no seal-in so the motor only runs while the button is held
The jog rung — no seal-in, so the motor runs only while the button is held.

The wiring picture

How the I/O maps to the motor

The push-buttons and the overload contact wire into the PLC inputs. The PLC solves the ladder and energises the Forward and Reverse contactor coils on its outputs. The contactors — in series with the overload — switch three-phase power to the motor. The PLC never carries motor current; it just commands the contactors.

Motor control PLC wiring diagram: Start, Stop and Forward/Reverse push-buttons and a normally-closed overload wire into PLC inputs; the PLC drives Forward and Reverse contactor coils that switch the three-phase motor
Motor-control I/O — buttons and overload in, contactor coils out, motor switched by the contactors.
Motor control PLC terminal wiring — a Start and Stop push-button and a normally-closed motor overload contact land on the PLC input terminals, sharing the field-device commonA PLC terminal strip wiring view: a switch wired to an input terminal and a lamp wired to an output terminal, with numbered terminals.TERMINAL STRIP0VI0I124VO0O1switchlampfield wiring to numbered terminals
Field wiring close-up: the Start, Stop and normally-closed overload devices landing on the PLC input terminal block.

Reduced-voltage starting

DOL vs star-delta vs VFD

Direct-on-line (DOL) throws full voltage at the motor instantly — simplest wiring, biggest inrush current. Star-delta reduces starting current by starting the motor in star, then switching to delta after a PLC on-delay timer expires; that timer-driven contactor sequence is a great ladder-logic exercise. A VFD ramps the motor electronically and adds speed control. You can build and test the DOL and star-delta logic here; a VFD is a drive, not ladder logic.

Commission DOL, reversing and star-delta circuitsOpen the VFD commissioning simulator
Comparison table of DOL vs star-delta vs VFD motor starting controlled from a PLC: starting current, contactors needed, PLC timer, speed control, and wiring complexity
DOL vs star-delta vs VFD — starting current, contactor count, and where a PLC timer comes in.

Interlock safety checklist

  • Stop wired normally-closed — fail-safe on a broken wire.
  • Overload wired normally-closed in series with the coil.
  • Forward rung interlocked by a normally-closed Reverse contact.
  • Reverse rung interlocked by a normally-closed Forward contact.
  • Both contactors can never energise at the same time.
  • Add a transition delay before reversing a spinning motor.
Motor control interlock safety checklist: fail-safe normally-closed Stop, normally-closed overload, forward and reverse cross-interlocks, and a transition delay before reversing
The non-negotiables of a safe motor-control circuit.

Build it yourself

How to build a forward/reverse circuit

The fastest way to learn motor control is to build it in the right order: get a start/stop seal-in working, duplicate it into a Forward and a Reverse rung, then add the cross-interlock contacts and prove the two contactors can never energise together.

Flowchart for building a forward reverse PLC motor control circuit: start with a start/stop seal-in rung, duplicate into forward and reverse rungs, add normally-closed interlock contacts, then test both contactors never energise together
Build order for a forward/reverse circuit — seal-in first, interlocks last.

Practice the rungs

Motor-control scenarios to drill

These are the rungs every controls technician is expected to write from memory. Build each one in the simulator, force the inputs, and watch the seal-in and interlocks behave before you ever touch a real contactor.

Start / Stop seal-in

Three-wire control with a fail-safe normally-closed Stop — the classic first rung.

Build it in the simulator →

Forward / Reverse

Two seal-in rungs cross-interlocked so both contactors can never energise.

Build it in the simulator →

Jog (inch)

No seal-in — the motor runs only while the Jog button is held.

Build it in the simulator →

Star-Delta start

Line + star contactors, then an on-delay timer drops star and pulls in delta.

Build it in the simulator →

Overload trip

A normally-closed overload that drops the motor out fail-safe when it opens.

Build it in the simulator →

Reversing with delay

A transition delay that prevents reversing a still-spinning motor.

Build it in the simulator →

Keep going

Where to practice next

Motor control is one circuit in a bigger toolkit. Once the seal-in and interlocks feel automatic, branch out into the wider ladder library and the wiring side of the panel.

  • PLC simulator — the full browser PLC with scored scenarios across timers, counters, and sequencing.
  • Ladder logic simulator — a focused ladder editor for building and testing rungs like these.
  • PLC wiring simulator — practise wiring push-buttons, overloads, and contactor coils to PLC I/O.
Questions

Motor control PLC FAQ

Motor control is the set of ladder-logic rungs a PLC uses to start, stop, seal in, reverse, jog, and protect an electric motor. The PLC reads push-buttons and an overload contact on its inputs, then energises the motor contactor coils on its outputs. The classic building blocks are the three-wire start/stop seal-in rung, the forward/reverse interlock, the jog (inch) rung, and reduced-voltage starting like star-delta.

Build your first motor-control rung now.

Start/stop seal-in, forward/reverse interlock, jog, and star-delta — all in the browser.

Open the PLC simulator →Try the ladder logic simulator

Technical reference and worked-example guide

PLC motor control: field reference

Direct answer

The learner can build and test stop-priority logic, permissives, interlocks, run proof, fault response and defined restart behavior.

Written for pLC and electrical learners implementing motor requests while separating software state, output interface, starter or drive, motor and process proof.

a qualified technician reviewing a locked-out motor starter, VFD, motor, schematic and meter at a training panel while studying PLC motor start-stop, reversing, interlocking and feedback logic
System map / 02

NODE 01observable

Definition

Motor and load, operating modes, commands, permissives, interlocks, outputs, starter or drive, feedback, faults, stop category and restart policy.

NODE 02observable

Signal path

Operator or sequence request through PLC arbitration and output to power device, motor response and independent running or process feedback.

NODE 03observable

Worked example

Local or automatic start, proven run, controlled stop and repeated restart from known states.

NODE 04observable

Limits

Simultaneous forward and reverse, welded output, failed feedback, overload, lost permissive, stop during transition and power return.

NODE 05observable

Common mistake

A mode, command, permissive, logic, output, starter or drive, motor, feedback or load defect.

NODE 06observable

Verification

The control reviewed against risk requirements and validated on the safeguarded target machine.

Answer surface / 07

How do you program motor start and stop in a PLC?

Define stop priority, start request, seal-in or state ownership, permissives, interlocks, output command, run feedback, trip behavior and restart policy, then test each state.

Should a PLC output drive a motor directly?

No. The PLC output normally controls an appropriately designed interface such as a starter or drive; motor power and protection belong to the electrical architecture.