An automated car parking system uses barriers, sensors and a ticket machine. (a) Describe the sequence of events that occurs when a car arrives at the entra...
Question 1 Report
An automated car parking system uses barriers, sensors and a ticket machine.
(a) Describe the sequence of events that occurs when a car arrives at the entrance to the car park. [4]
(b) Describe how the system knows when the car park is full. [1]
Answer Details
(a) The sequence of events when a car arrives at the entrance:
- A presence sensor (such as an inductive loop embedded in the road surface, or an infrared beam across the entrance) detects that a vehicle has arrived at the entrance barrier. [1]
- The system activates the ticket machine, which issues a ticket showing the entry time, date, and possibly a barcode or reference number. The driver takes the ticket. [1]
- Once the ticket is taken (detected by a sensor in the dispenser), the microprocessor sends a signal to the barrier motor to raise the barrier, allowing the car to enter. [1]
- After the car passes through (detected by a second sensor beyond the barrier), the barrier is automatically lowered again and the system's available-spaces counter is decremented by one. [1]
(b) The system maintains a counter that tracks the number of vehicles inside the car park. Each time a car enters, the counter increments by one; each time a car leaves, it decrements by one. When the counter equals the car park's total capacity, the system knows the car park is full and can display a "FULL" sign and prevent the entrance barrier from opening. [1]
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