08Level 3

Conveyor belt with box counter

A sensor counts the passing boxes. When a batch of 6 boxes is complete, the belt stops and a light turns on until the operator starts a new batch.

Open in the simulator

The simulator is designed for computers (screens 1024 px or wider).

Virtual plant

Shown at rest. In the simulator the plant moves according to your program's outputs.

Inputs and outputs

Address	Name	Description
I0.0	START	Start push button (NO)
I0.1	STOP	Stop push button (NC: 1 at rest)
I0.2	BOX_SENSOR	Photocell that detects the boxes (plant)
I0.3	NEW_BATCH	Push button to start a new batch (NO)
Q0.0	BELT	Belt motor
Q0.1	BATCH_READY	Batch complete light
C0	BOXES	Box counter of the batch

Program

Ladder diagram (LD)

Rung 1 — Counts the boxes; NEW_BATCH resets the count. The output means batch complete.
Rung 2 — Belt with seal-in; it stops when the batch is complete.

Structured text (ST)

(* Conveyor belt with box counter — converted from Ladder *)

VAR
  BOXES : CTU;
END_VAR

(* Rung 1: Counts the boxes; NEW_BATCH resets the count. The output means batch complete. *)
BOXES(CU := BOX_SENSOR, R := NEW_BATCH, PV := 6);
BATCH_READY := BOXES.Q;

(* Rung 2: Belt with seal-in; it stops when the batch is complete. *)
BELT := (START OR BELT) AND STOP AND NOT BOXES;

Instruction list (IL)

(* Conveyor belt with box counter — converted from Ladder *)

VAR
  BOXES : CTU;
END_VAR

(* Rung 1: Counts the boxes; NEW_BATCH resets the count. The output means batch complete. *)
  CAL   BOXES(CU := BOX_SENSOR, R := NEW_BATCH, PV := 6)
  LD    BOXES.Q
  ST    BATCH_READY

(* Rung 2: Belt with seal-in; it stops when the batch is complete. *)
  LD    START
  OR    BELT
  AND   STOP
  ANDN  BOXES
  ST    BELT

Step by step

1Press ▶ Run (F5) and press START: the belt moves and the BOXES counter adds one for each box that passes the sensor.
2Watch the counter's CV value in rung 1. The counter counts edges: a box adds only once, even if it takes a while to pass.
3At 6 boxes, the counter output turns on BATCH_READY and its NC contact in rung 2 stops the belt.
4Press NEW_BATCH to set the count to zero and then START to begin another batch.

Open in the simulator