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CONVEYOR SCENE v2.000
STOPPED
SIM SCAN: —
DISCONNECTED
Drag=Orbit  ·  Scroll/+−=Zoom  ·  Arrows=Orbit
BRIDGE WS URL: Run acc-modbus-bridge.js first, then click CONNECT
ACC MODBUS BRIDGE  —  INSTALL GUIDE

What is the ACC Modbus Bridge?

A small Node.js program that runs on your PC and connects this browser scene to a real Modbus TCP or Modbus RTU master such as a PLC, SCADA system, or Modbus Poll software.

Step 1 — Download the installer

Download the zip file and extract it to a folder on your PC.

Download acc-modbus-bridge.zip

Step 2 — Install Node.js (one-time)

The bridge requires Node.js. Download the LTS version from nodejs.org and run the installer.

Step 3 — Run the installer

  1. Extract the zip file
  2. Windows: double-click install.bat
  3. macOS: double-click install.command
  4. Follow the on-screen prompts to choose Ethernet (TCP), Serial (RTU), or both
  5. The installer creates a start-modbus-bridge shortcut for you

Step 4 — Start the bridge

  1. Double-click start-modbus-bridge.bat (Windows) or start-modbus-bridge.command (macOS)
  2. Keep the terminal window open while using Modbus

Step 5 — Connect this scene

  1. Confirm the Bridge WS URL is ws://127.0.0.1:8502
  2. Click CONNECT — the badge turns amber when linked

Modbus Address Map — Conveyor System

  1. Coil 00001  →  Y1 Motor Run (master writes)
  2. Coil 00002  →  Y2 Direction — OFF=FWD, ON=REV (master writes)
  3. DI   10001  →  X1 Start PB N.O. (master reads)
  4. DI   10002  →  X2 Stop PB N.C. — true at rest (master reads)
  5. DI   10003  →  X3 Left End Sensor (master reads)
  6. DI   10004  →  X4 Right End Sensor (master reads)

More tutorials at  accautomation.ca  ·  YouTube @ACCautomation

OUTPUTS Y COILS
Y1
Motor RunConveyor Drive Enable
Y2
Motor DirectionOFF=FWD  ·  ON=REV
Drag to orbit  ·  Scroll to zoom
► ► ►
INPUTS X CONTACTS
X1
Start PBN.O. Momentary
X2
Stop PBN.C. Momentary
X3
Left End SensorProx / Auto-detected
AUTO
X4
Right End SensorProx / Auto-detected
AUTO

Sequence Log

Ready — Press RUN then START to begin a cycle POS: 0.00 SCAN #0

CONVEYOR SYSTEM SCENE

Bi-directional Belt Conveyor with End Sensors

A steel belt conveyor carries a product box between two proximity sensors. The belt runs in both directions under PLC control. This scene demonstrates direction control, seal-in circuits, and sensor-based reversing logic — all essential patterns in conveyor automation.

I/O MAP
AddressDirDescription
X1INStart pushbutton — N.O. momentary
X2INStop pushbutton — N.C. momentary
X3INLeft end sensor — box at left limit
X4INRight end sensor — box at right limit
Y1OUTMotor run — belt drives when ON
Y2OUTDirection — OFF=forward (right), ON=reverse (left)
FIVE STEPS TO PLC PROGRAM DEVELOPMENT

Use these five steps to develop your ladder program for this scene. Run standalone mode first to observe correct behaviour, then build and test your program in the ACC PLC Simulator.

STEP 1

Define the Task

A conveyor belt must carry a box from one end to the other and back in a continuous cycle. When Start is pressed, the belt runs forward. When the box reaches the right sensor, the belt reverses. When the box reaches the left sensor, the belt reverses again. This cycle repeats until Stop is pressed. Stop must halt the belt immediately at any point.

STEP 2

Define the Inputs and Outputs

Two manual inputs: Start (X1, N.O.) and Stop (X2, N.C.). Two automatic sensor inputs: Left Sensor (X3) and Right Sensor (X4), set by the scene when the box reaches each end. Two outputs: Motor Run (Y1) to start/stop the belt, and Direction (Y2) to control which way the belt moves. Direction only matters when Y1 is ON.

STEP 3

Develop the Sequence of Operation

Initial state: motor off, box at left end. On Start: motor runs forward (Y1=ON, Y2=OFF). When box reaches right sensor (X4=ON): reverse direction (Y2=ON), motor continues. When box reaches left sensor (X3=ON): forward direction (Y2=OFF), motor continues. Repeat. On Stop: motor off. Consider: what is the direction when the motor first starts? What if a sensor is already active when Start is pressed?

STEP 4

Develop the PLC Program

You will need rungs for: Start/Stop seal-in (Y1), and direction latch based on which sensor was last triggered (Y2). Use an internal coil (C bit) to latch the direction state so it persists between scans. The direction must not flip back and forth on the same sensor trigger.

STEP 5

Test the Program

Connect the scene, press RUN, and watch the box travel back and forth. Verify: (1) pressing Start begins movement; (2) the box reverses at each end; (3) pressing Stop halts the belt; (4) restarting after Stop continues in the correct direction. Check edge cases: what happens if you press Start exactly when a sensor is active?

© ACC Automation  ·  accautomation.ca