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Mission 46 · Pro PLC programming exercise

Green figure, on time

Run a crossing's six stages with their timers.

Run the crossing through green, amber, red, green figure, clearance and red-and-amber, each for its set time, and only after the traffic has had its minimum green.

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

A full crossing cycle

Test 1 of 3
Set by the testChecked by the testStep 13 of 13 · 28.6 s
Level
Applied
Time
About 30 min
Reward
+350 XP
Rig
3D pedestrian crossing traffic lights
Siemens editors
SCL, LAD
Rockwell editors
Structured Text, Ladder
Course stage
27. Machine lab 2: memory, timing and sequences
Automatic tests

What the tests check

  1. Traffic green with the red figure until a request.
  2. Traffic gets at least 10 s of green before amber.
  3. Amber 3 s, all-red 2 s, green figure 6 s, all-red 3 s, red-and-amber 2 s.
  4. The green figure never shows with traffic green or amber.
  5. WaitLamp lights from the press until the green figure appears.
  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

UK pelican and puffin crossings use these stages and similar timings, set by the highway authority.

A crossing that skips the amber or the clearance time surprises drivers and strands people in the road. The order and the minimum times are the safety.

Where you'd find thisStop the traffic, let people cross, and get the timings right

Every town has crossings like this. The controller follows a fixed order, with minimum times so drivers are never surprised and pedestrians always get long enough to cross.

  1. GreenTraffic flows
  2. AmberStop if you can
  3. Green figurePeople crossYou are here
  4. Red and amberGet ready
On a real site: places, parts and safety
  • High streets and school routes
  • Factory sites where people cross a forklift route
  • Car park exits and level crossings

Real crossing controllers are certified: they prove green to traffic and green to pedestrians can never show together.

Timings are set by highway engineers for the road width and the people who use it.

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

Keep going

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