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Mission 11 · Free PLC counter exercise

Count with a one-shot

One bottle covers the sensor for many scans. Count it once.

Turn BottlePulse ON for exactly one each time BottlePresent goes from OFF to ON. A pulse like this is called a . Count the pulses into Pieces. At three or more bottles, turn Done ON and ConveyorOn OFF. Reset clears Pieces and Done at once, but must not clear the edge memory.

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The 3D filling line this mission runs on
Test replay

Held sensor counts once

Test 1 of 4
Set by the testChecked by the testStep 10 of 10 · 740 ms
Level
Applied
Time
About 18 min
Reward
+250 XP
Rig
3D filling line
Siemens editors
LAD
Rockwell editors
Ladder
Course stage
5. Count an event once
Automatic tests

What the tests check

  1. One pulse when the turns ON. No pulse while it stays ON, or when it turns OFF.
  2. Each pulse adds one. At 3 or more, Done stops the conveyor.
  3. Reset wins over counting. A bottle still at the sensor is not counted again.
  1. Try it Use the buttons below the model and watch the rig respond.
  2. Test solution Every check runs on your code in one press.
  3. Replay If one fails, step through it one scan at a time to see why.
Why it matters

Where you’d see this on site

A packing line counts each bottle as it reaches a light sensor. A bottle that stays in the beam still counts only once.

An extra count can send out a batch with too few bottles. Resetting the count must not count the bottle at the sensor a second time.

Where you'd find thisPutting drinks into bottles

At a soft-drinks factory, empty bottles arrive on a moving belt. A sensor tells the controller when a bottle is under the filling nozzle. The valve opens, fills the bottle, then closes before the belt moves again. Caps and labels go on before the bottles are packed.

  1. Empty bottlesThe belt brings them to the nozzle
  2. Fill each bottleStop it, fill it, then let it moveYou are here
  3. Add caps and labelsSeal the drink and name the product
  4. Pack the bottlesPut finished bottles into boxes
On a real site: places, parts and safety
  • Soft-drinks factory — filling bottles without spills
  • Dairy — putting milk into bottles
  • Cleaning-products factory — measuring liquid into containers
  • Food packaging line — counting bottles before packing

If the filling valve opens without a bottle under it, liquid spills onto the belt. If the line jams, the valve must not keep filling.

Real conveyors need guards. The power must be safely locked off before anyone clears a blockage. The Stop input here is not an emergency stop.

The sizes, timings and cutaways are teaching choices, not a drawing of any one real installation.

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