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Practice missions
Mission 22 · Pro auto and manual mode exercise

Hand over between Auto and Manual

Keep the pump steady when control changes hands.

AutoMode picks what runs the pump: the tank level (Auto) or the Manual buttons. In Auto, PumpOn starts below 30% and stops at 70%. In between, it keeps its last state. In Manual, ManualStart latches PumpOn on and ManualStop wins. Switching mode must not change PumpOn on its own. If the new mode is already asking for a change, it may act on the switch or the next one. A Fault, or losing Permit, always stops the pump at once.

This mission is part of ProTry the full course, every mission and the expert challenges free for 7 days. No card needed.
The 3D process tank this mission runs on Pro mission
Test replay

Auto remembers both sides of the band

Test 1 of 12
Set by the testChecked by the testStep 13 of 13 · 1 s
Level
Applied
Time
About 20 min
Reward
+250 XP
Rig
3D process tank
Siemens editors
SCL, LAD
Rockwell editors
Structured Text, Ladder
Course stage
11. Hand control over
Automatic tests

What the tests check

  1. Auto starts below 30% and stops at 70%. Manual uses ManualStart and ManualStop, and Stop wins.
  2. With nothing asking for a change, switching mode either way keeps the pump ON or OFF, scan after scan.
  3. A Fault, or losing Permit, stops the pump in both modes, even on the switch scan.
  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

An engineer switches a tank-filling pump from Auto to Manual so they can test it with the buttons.

Changing mode on its own should not cut off a fill or start an idle pump. Manual buttons must still obey an empty supply or a failed motor.

Where you'd find thisMaking one batch of drink

At a drinks factory, valves let measured amounts of water and syrup into a mixing tank. An electric mixer blends them into one batch. An outlet valve then sends the drink to a holding tank. Filling machines bottle it from there.

  1. Ingredient tanksHold the water and syrup
  2. Mixing tankFill, mix and measure one batchYou are here
  3. Holding tankKeeps the finished drink ready
  4. Bottle fillerPuts the drink into bottles
On a real site: places, parts and safety
  • Drinks factory — blending water and syrup
  • Paint factory — mixing ingredients into a consistent colour
  • Water-treatment works — preparing a measured chemical mixture
  • Brewery — heating water for washing equipment

A full tank does not close its own inlet. Water keeps arriving until the valve closes, so an open inlet can flood the room.

A heater that is not covered by liquid can overheat. Real tanks have separate safety devices as well as the PLC programme.

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

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