Pedestrian crossing

The brief

Client

Millbrook Council

Site

School Road crossing

Work order

MC-2606

Industry

Traffic and civil

Task code

PLC-06

Difficulty

Intermediate

Type of work

Programming

Run a push-button crossing through amber, walk and clearance on timers, never showing Walk to pedestrians while cars can move, and ignoring presses during the cycle.

What you do

1. Read the client brief and the tag table: 6 tags, 1 inputs and 5 outputs.
2. Write the logic in ladder, Structured Text or SFC.
3. Press Simulate and watch the plant answer your program.
4. Run the factory acceptance test and fix what fails.

Skills you practise

• Sequential control with timers
• One-shot (ONS) edge detection
• Safety interlocking of outputs
• State thinking

What the test checks

The factory acceptance test runs 5 numbered tests against your program. The numbers in the brief are drawn per learner. The tests are:

• Cars keep green until somebody presses
• A press runs the whole cycle with the right times
• Presses during the cycle are ignored
• Holding the button runs one cycle only
• The crossing is ready for the next pedestrian

In this lab

• Ladder, Structured Text and SFC in one studio
• A plant that answers: motors, tanks, conveyors
• Numbered tests mark your program