Challenges
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PLC programming challenges
Challenge 04 · Code it · Pro

Sound the horn before it moves

Three seconds of warning before the belt starts.

Start must not move the belt straight away. Sound Horn for 3 seconds first, then stop the horn and run Conveyor. Stop at any time stops the belt and the horn, and cancels a warning that has not finished. Start while the belt is already running does nothing.

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The 3D conveyor box sorter this challenge runs on Pro challenge
Test replay

Horn first, then the belt

Test 1 of 4
Set by the testChecked by the testStep 5 of 5 · 3.7 s
Level
Medium · 20 points
Kind
Code it
Time
About 15 min
Pass rate
New
Machine
3D conveyor box sorter
Siemens
LAD and SCL
Rockwell
Ladder and Structured Text
Beckhoff
Structured Text
Automatic checks

What the checks test

  1. Start sounds Horn at once, with Conveyor still OFF.
  2. After 3 s the horn stops and Conveyor runs.
  3. Stop cancels a warning: no horn, and the belt never starts.
  4. Stop stops a running belt.
  5. Start while running does not sound the horn again.

The checks run 4 tests on the machine, scan by scan: Horn first, then the belt; Stop cancels the warning; Stop stops a running belt; Start while running does not sound the horn.

On site

Where you’d find this

On a parcel sorting line, a horn sounds before the belts start, so anyone reaching in can step clear.

Belts that start without warning catch hands and sleeves. Many sites make a start-up warning part of the machine's risk assessment.

The machine

How it should behave

Start
Horn for 3 s, then the belt runs.
Stop
Stops belt and horn, and cancels a warning.

Press Run, then Start. The horn sounds for 3 s before the belt moves. Press Stop during the horn and the belt never starts.

Keep going

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