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Mission 07 · Free PLC timer exercise

Wait for the process

Start the pump only after a 200 ms hold.

Turn PumpOn ON only after Start has been held for 200 ms, so a quick tap does nothing. Use an , which waits a set time before switching ON. When Start is released, PumpOn turns OFF and the timer goes back to zero.

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The 3D pump skid this mission runs on
Test replay

Pump starts after exactly 200 ms

Test 1 of 3
Set by the testChecked by the testStep 2 of 2 · 220 ms
Level
Foundation
Time
About 8 min
Reward
+100 XP
Rig
3D pump skid
Siemens editors
SCL, LAD
Rockwell editors
Structured Text, Ladder
Course stage
4. Wait, then act
Automatic tests

What the tests check

  1. PumpOn stays OFF while Start has been held for less than 200 ms.
  2. PumpOn turns ON once Start has been held for 200 ms.
  3. Releasing Start resets the timer. The next press waits the full 200 ms 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

At a factory wash station, the operator must hold Start for a moment before the pump runs. A quick tap should do nothing.

If every accidental tap starts the pump, water sprays into the wash area. The delay tells a deliberate hold from a brush of the button.

Where you'd find thisWater for the top floors

In a block of flats, a basement tank holds water from the mains. Two pumps push it up to the taps above. One runs while the other waits as a spare. A low-water switch stops the pumps before the tank runs dry.

  1. Street mainsWater enters the building
  2. Storage tankHolds a supply for the pumps
  3. Water pumpsPush water to the floors aboveYou are here
  4. Taps upstairsResidents use the water they need
On a real site: places, parts and safety
  • Block of flats — pushing water up to the top floors
  • Brewery — sending hot water to a brewing tank
  • Water-treatment works — moving water between filter tanks
  • Office building — pumping water round the heating pipes

A low-water switch can take away permission to run. The pump must stop before it runs dry and damages its seal.

The PLC can say ON even when a pump has failed. Check the measured flow as well as the command.

The Stop input in these exercises is not an emergency stop. Real machines also need guards, emergency stops and a safe way to cut the power.

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

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