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Practice missions
Mission 70 · Pro PLC programming exercise

Grey is normal

Save colour for the things an operator must act on.

Fix the compressor's operator screen so normal running looks calm and grey, and only a real problem shows in colour. Then make the flag low pressure and a motor that won't run, with no false alarms.

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The 3D air compressor station this mission runs on Pro mission
Test replay

A normal cut-in raises no flag

Test 1 of 4
Set by the testChecked by the testStep 4 of 4 · 1.1 s
Level
Applied
Time
About 20 min
Reward
+300 XP
Rig
3D air compressor station
Siemens editors
Ladder (LAD), SCL
Rockwell editors
Ladder, Structured Text
Beckhoff editors
Structured Text
Course stage
36. Operator screens 1: grey is normal
Automatic tests

What the tests check

  1. Normal running and stopped equipment look calm and grey, not green and red.
  2. Low pressure stands out with an alarm marker beside the value, showing its priority.
  3. LowPressure is in service below 5.0 bar, and clears at 5.5 bar or above.
  4. Out of service, LowPressure stays however low the pressure falls.
  5. MotorFault is TRUE only after CompressorRun has been ON for 2 s with MotorRunning OFF.
  6. The station control still works: CompressorRun cuts in below 6.0 bar.
  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 factory's compressor house is often watched from a screen in the maintenance office, one screen among a dozen.

If every screen is green and red all day, nobody spots the one compressor that has tripped until the air tools stop.

Where you'd find thisKeep compressed air ready without running the motor all day

Almost every workshop and factory has a compressor like this in a back room. It feeds air tools, spray guns and the pneumatic cylinders on machines. The PLC starts the motor when the pressure falls to a lower limit and stops it at an upper limit, so the motor rests between charges.

  1. Air intakeFiltered room air
  2. CompressorSqueezes the air
  3. ReceiverStores it under pressureYou are here
  4. WorkshopAir tools and machines
On a real site: places, parts and safety
  • Vehicle workshops and body shops
  • Packaging and assembly lines with pneumatic cylinders
  • Joinery shops and small factories

Isolate and vent the receiver before working on the pipework: stored air is stored energy.

Never adjust or block a safety valve to stop it lifting.

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

Keep going

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