Control : Pedestrian Crossing

This control system is used to operate a simple pedestrian road crossing involving just one set of traffic lights. When a pedestrian wants to cross the road she presses the button located near the crossing. After a short pause the traffic lights will turn to red so that the pedestrian can cross. Red and green men lights and a buzzer are used to indicate when it is safe to cross.

The important components of this system are :

• A set of traffic lights to control the flow of traffic
• A set of pedestrian lights.
• A buzzer and wait light.
• A button for pedestrians to press when they want to cross the road.

Input and Output Devices

The control system has these input and output devices :

Flowchart

The operation of the control system can be described by this flowchart :

Note that there is no stop box because the crossing once started never stops operating unless something goes wrong.

GCSE ICT Companion 04 - (C) P Meakin 2004