Practice missions
Practise in
0 XP
Practice missions
Mission 12 · Free PLC counter exercise

Count bottles as they leave

Count each bottle as it clears the sensor, not as it arrives.

Turn BottlePulse ON for one when BottlePresent goes from ON to OFF. That change is a : the moment a bottle leaves the . Count each pulse into Pieces. At three or more, turn Done ON and ConveyorOn OFF. Reset clears Pieces and Done at once, but must not wipe the sensor's last reading.

Free, with no sign-up. Create a free account to keep your progress on every computer.

The 3D filling line this mission runs on
Test replay

Count departures, not arrivals or clear scans

Test 1 of 3
Set by the testChecked by the testStep 10 of 10 · 860 ms
Level
Applied
Time
About 10 min
Reward
+150 XP
Rig
3D filling line
Siemens editors
SCL, LAD
Rockwell editors
Structured Text, Ladder
Course stage
5. Count an event once
Automatic tests

What the tests check

  1. BottlePulse is ON for one scan, and only when the sensor goes from ON to OFF.
  2. Pieces goes up by one for each bottle that leaves. At 3 or more, Done turns ConveyorOn OFF.
  3. Reset wins over counting, even on the scan a bottle leaves. Letting go of Reset adds no extra pulse.
  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 once it has fully passed a light sensor. A bottle still blocking the beam has not left yet.

Counting bottles as they leave proves they have cleared the station. Counting on arrival could include a bottle still stuck at the sensor.

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.

Keep going

Next in the course