Author: © 2014 Seyedreza fattahzadeh
Binding: E-book in PDF format
Format: PDF file
Number of pages: 116
As the title of the text implies, the purpose of this project is to show the reader how he can design and implement a PLC based Parking system. In short, the PLC based system will keep track of 16 cars in the parking area. It will not allow more than 16 cars to park. It will show the number of lots unoccupied, will automatically raise the Gate arm to allow cars into the parking lot or leave it. It keeps track of amount of time a car is parked, the time driver is leaving the parking lot, shows current and exit Time and Date and display them on either a HMI or on a PC based HMI device. PLC will finally calculate cost of parking for each car parked in the Parking. When amount is paid, the parking operator depresses a paid button, the exit arm gate is raised, and one unit is added to the total number of vacant cars in the Parking lot.
Students learn how to write simple circuit programs to get familiarized with the application of a PLC but in the automation field when one is applying for a job as a PLC programmer, the employer will NOT ASK him to write a simple PLC program on the contrary , he will either assign him a new Functional Specification of some new system and will expect him to develop a control program and implement the hardware or He might ask him to alter a pre-written circuit program to include some more function and edit it based on a new defined specification. That means he would need to checkout a printed document of a circuit program consisted of sometime more that tens of pages, understand before to start modifying it.
I have come up with a solution for those that do have the beginning knowledge on how to work with a typical PLC’s instructions BUT they need to practice on how to take a Functional Specification and turn it into a working PLC control program which is controlling lots of digital and analog functional blocks by authoring this new text title.
In this project, we are dealing with design and implementation of an Automated Parking System using a typical mid range PLC in our case: a SIMATIC S7-300 model of a PLC plus WinCC software based PC or a typical HMI display devices.
1- CONTROL PLC PROGRAM
According to figure 1, control program on PLC must be able to control 22 digital input signals (16toggle switches that each represents a parked car in the parking area + 4 arm gate limit switches +1 paid button + 1 break beam sensor) and control 14 output loads (8 data signals to control a 2 digit numerical display+ 4 other signals to control two arm gate dc motors to turn them either cw or ccw + 2 signals to control 2 red and green LEDs). With all these I/Os and PCB wired to PLC’s I/O, the control program will control all of these devices independently. Total number of PLC input / Output terminals are used 22 and 14 respectively! Schematic diagrams of all PCBs are given in the text and you can even build any of them if you wish. Ladder Logic program developed for this project has been consisted of hundreds of instructions, FB (functions blocks), and DBs (data bases). All these networks that most of time each network is consisting of more than 5 to 10 simple instructions such as AND, OR ,Timers, counters… etc must all function in right way in order the whole system to operate in a harmony. So to develop a PLC control program to control all of these I/Os , a numerical displays and Lights all in harmony is not easy! And when you do something like this on your own that is the time that you can tell the employer “YES I CAN DO IT” with lot’s of confidence. And since application of HMI devices nowadays in processes is a de facto standard, I have developed two more application software programs to allow system operator to monitor all activities related to this the Automated Parking system on a PanalMaster, and WiCC based HMI and PC devices as well.
2- PanelMaster HMI program:
PM Designer is a simple yet powerful programming language designed for developing programs for a typical HMI display. If you are not familiar with how to design a typical screen for a general HMI display panel, you may refer to Appendix A of manual where you will be provided with some basic tutorial information about the PM Designer software. Appendix A also shows you how to apply the design idea with respect to this project.
This second program which comes with the text, allows a typical HMI device to be connected to a PLC by which operator will be able to control or monitor all activities related to project independently. At any instances, just by glancing at the HMI’s screen, an operator can find out how many vacant and occupied slots are available, and when a car is leaving the garage, how much that particular driver owns the parking management. And the operator allows the leaving car to exit the garage just by depressing a paid button which causes the exit arm gate to be raised to allow the paid driver leave the parking area. See the next figure.
3- Application of SIMATIC WinCC program
In chapter 4 of the text, we are going to develop a WinCC explorer based HMI screen program to view all of the good things happening on the PC’s monitor as well, such as the number of UN-occupied spaces, parking costs for each driver whose car has been parked in the parking area etc.
The application program which comes with the project also shows you how to develop a program with WinCC and to implement it to a HMI screen on your PC’s monitor. In this case, you can also can view all the activities that you could see on the HMI device but this time on your PC’s monitor as well. When the WinCC application is executed, you will have a screen similar to the one shown in the next figure. Notice that slot number 1, 3, 5, 7…15 are the unoccupied ones and 6,8, 13,14, and 16 are occupied ones. So the total number of free space is 16-5 = 11 as shown on the top right side of the operator’s PC monitor. Current time is 5:23 and date is 14, 07, 2013.
Questions and answers related to this project