Contrary to the camera-based Parking Guidance System (PGS), the sensor-based PGS relies on ultrasonic sensors to detect the vacancy of parking spots. Accordingly, one ultrasonic sensor is mounted on top of each parking spot. The sensors communicate over a bus cable and are powered by a power cable. The cables run in daisy chain topology and terminate in the zone control unit (ZCU). There’s a limitation for the zone controller unit regarding the number of sensors it can handle. The central control unit (CCU) controls the ZCUs and connects the system to the network. The PGS software provides a graphical interface for the operator indicating the number of vacant and occupied spaces.
A Parking Guidance system based on ultrasonic sensors comprises 4 main components:
The Sensors use ultrasonic waves to detect the vacancy of parking spots. They can be either wired or wireless. Wireless sensors are usually mounted under the cars in outdoor spaces. Wired sensors come in two types depending on their location. The first type is installed in-front of the car and detects in a diagonal fashion. This type usually comes combined with the light indicator. The second type is installed in the ceiling directly above the car and usually comes separate from the light indicator.
2. Light Indicators
They are installed at the edge of the aisles to indicate the status of the parking spot. Usually, three colors are used to indicate the vacancy: red for occupied, green for vacant, and blue/orange for reserved. Sometimes the blue color is used to indicate a parking spot for the handicapped.
3. Signage Displays
Indoor displays show the count of available spaces as well as the direction of the cars’ pathway. Outdoor displays, or totems, are usually installed at the entrance of the parking lot indicating the number of vacant spaces in each floor; in case the parking was multi-floor. Displays need a separate power source.
4. Control Units
Control units can be either zone control unit (ZCU) or a central control unit (CCU). The ZCU provides the data and power connection to the sensors. Since the ZCU is limited to a certain number of sensors, couple of ZCUs usually exist in one application. The CCU is the central unit that controls all ZCUs. It also provides an interface to the network.
The server communicates with the system over the network or serial port. The PGS software provides the interface for the operator and end-user to the system. Through this interface, the user can monitor the parking availability status in real-time. Different vendors provide many other rich features including integration with lighting control and other third party systems.