Preface： With the rapid development of China's economy, the family vehicle and social vehicles are growing rapidly, parking lot construction has become an indispensable part. And only if a parking lot is equipped with a good control system can it save manpower, improving the utilization rate of parking space, ease the contradiction between supply and demand of parking spaces. The system adopts H01ZB module and PC2ZB module of Haiwell company to build wireless Zigbee net and to communicate with touch screen, H01ZB wireless module is based on the re-transmission mechanism of Zigbee agreement, and add break response re-transmission mechanism in the application, which greatly enhance the stability of the communication,we haven’t found any communication interruption and bad connections during the use,and it provide convenience for the car owners to park quickly.
Key words : Haiwell PLC H01ZB module PC2ZB module
1. Controlling requirements
Schematic diagram of control
1.1. Using LED monochrome display screen to display the number of remaining cars in the garage door. The entrance gate will be opened and let vehicles enter to park when there are parking spaces.
1.2. Automatically collect the status of vehicles into the garage, using card form to get card number to enter the parking lot and to guider users to find the parking place immediately. And it can reduce the time of parking.
1.3. An ultrasonic parking sensor is arranged on the upper part of the parking space in the parking area, which is for preventing the phenomenon of indiscriminate parking and checking the right position of vehicles.
1.4. The vehicles owners use card form when they leave the parking lot, to calculate automatically the parking time according to the entering time and leaving time, and to calculate automatically the fee according to the parking time and charge standard. The vehicles can leave after paying the fee.
2.1 Hardware system structure
In the control system of this paper, the collected signal is logic switch signal, The number of input points increases with the increase of the number of parking space. This requires PLC to have a strong point of expansion capabilities , what’s more, Haiwell PLC can expand to 7 modules, most expansion modules also support remote function, and it can read corresponding point information by Modbus agreement. The mini-controller has the same ability with medium-size controller, therefore there is no problem to solve the control system of parking lot. In addition, PLC need to communicate with LED monochrome display, to send the information of remaining parking spaces, in the same time, PLC also need to collect the information of the car, to achieve the monitoring of the card number. The card information as important information can transmit and communicate at any time by the system. So the communication will be busy in the system, it requires PLC has strong communication ability. And communication is the advantage of the Haiwell PLC, it’s easy to use. Only one communication command to complete the complex communication function. It can greatly reduce the debugging time of the system and improve the efficiency of the system. Considering the above system requirements, choose Haiwell PLC as the controller of the control system.
2.2 Controller and module selection and using
PLC host selection is generally in the function to meet the requirements of the premise. The system is considered to use register components mostly, so we choose H series host. There is RS232 port and RS485 port in the H series PLC, every communication port has the same function, and it can program and formnetwork. It can be used as the main station or slave station. In the system, the card reader exchanges the information with PLC by RS232 communication port in the host, LED monochrome display screen uses RS485 in the host plc to communicate. The system in order to allow the users to save time, put the touch screen in the place where the users can take the card. Using H01ZB module and PC2ZB module realize wireless communication between PLC and touch screen. H01ZB module is hung directly behind the host plc. PC2ZB is connected with touch screen, The following figure is a schematic diagram of the network:
After normal communication, the users can realize clearly the layout of parking lot and remaining parking spaces by touch screen. The screen of the touch screen will display the overall layout of the parking lot and the most of the parking spaces, which can lead users arrive at parking area immediately. The following figure is one of the areas of the touch screen display screen.
3. System advantages
1.Strong communication and simulation capabilities
The Haiwell PLC has a lot of powerful innovative convenience instructions, No matter what communication is, the protocols only need one communication command, the complex communication function can be completed. It is the first with a built-in simulator PLC programming software in China, the full realization of the PLC simulation running. Either ordinary procedures, or communication simulation program can be simulated. Greatly reduce the site commissioning time, reduce the difficulty of debugging, improve the efficiency of debugging.
2. Wireless network is simple and convenient, high communication stability
Using Haiwell company H01ZB module and PC2ZB module to build net is simple and convenient, there is no need to configurate ZigBee parameters, users only need to put the DIP switch. The communication has high stability,Based on the ZigBee protocol itself the re-transmission mechanism is added on line re-transmission mechanism on application layer.
3. Reduce manpower, improve efficiency and save cost
The parking control system improves the work efficiency of modern humans, Also greatly saves the manpower and material resources, reduce the company's operating costs. Regulate the parking order, to avoid the phenomenon of arbitrary charges . Make the whole management system becomes more safe and reliable.
4. Visual interface, allowing users to reduce the parking time
When users take the card in the line, users can view through the touch screen to see the entire layout of the parking area and the most simple route to the parking place where there are more parking places. It reduces the users’ parking time. Although it's just a little bit of time, the users’ experience is quite different from now on. Humanized design can always attract more users.