Design and Implementation of a Secured Entry/Exit Car Parking Lot Using Programmable Logic Controller (PLC) Abstract 1,2 Department of Electrical/Electronic Engineering, University of Lagos, Akoka 3 Department of Computer Engineering, Yaba College of Technology, Lagos E-mail: 1 dodedele@unilag.edu.ng 2 alarape2000@gmail.com Contacts: 1 08053675491, 2 08099748141, 3 07011303502 Many Organizations and Institutions have seen explosive growth in the number of visitors and patrons due to the nature of services they render. As a result, frustration with parking of vehicles has become a major concern. Patrons and visitors often do not know whether parking spaces are still available to them until they arrive the parking lot. The engagement of the best security personnel to man the entry and exit points of the companies car parks have not offered the best solutions to the challenges being confronted by the drivers when trying to locate spaces to park their vehicles. To overcome these challenges, modern technologies need to be deployed. In this paper, a secured entry and exit car parking lot using a Programmable Logic Controller is designed and implemented. The program is implemented using Ladder Logic employing basic controls such as pushbuttons, counters, timers and lamps. The control system monitors and controls the entry to and exit from the parking lots and also prevents entry to any car when the park capacity of 100 is reached. The designed system can be used for many other applications and can easily be enhanced to accommodate more than 100 cars captured in this work. Parking becomes easy, cost effective and ultimately results in pollution free society using the designed system. Therefore, modern technology such as the PLC should be deployed for effective car park management system. Keywords: Secured, Entry/Exit, Parking Lot, PLC, Ladder Logic, Input/output 1.0 Introduction The advancement and progress of nations is measured by the possibility of their use and application of latest invented technologies in all aspects of life. Control engineering is one aspect of Electrical Engineering which has been given a great deal of attention by many researchers. Automation has become a great concern to many sectors such as industrial, agricultural, health, educational and infrastructural sectors. Automatic control systems have emerged as an integral part of telecommunications, electricity, fuel and other applications [1, 2]. No doubt, these sectors determine the wealth and prosperity of every nation, so it must be given the required attention. Today, almost all industrial processes are automation driven. Be it Oil and gas, manufacturing, telecommunications, Marine, Power and Agriculture, PLCs are the hearts of all industrial controls. This paper is devoted to the use of control systems (PLC) to implement a secured entry and exit gates for a car parking lot. The control system will play a major role in monitoring and controlling the entry to and exit from the parking lots and also prevents entry to any car when the park capacity of 100 is reached. This has been necessitated as a result of the challenges been confronted by the patrons and visitors of organisations and institutions in their quest to secure parking spaces with little or no bottlenecks. Investigations have shown that such patrons arrive and roam around the parking lots before they discover the spaces were occupied because the car parks are being managed manually. In this work, the driver doesn t have to enter the parking lot before being informed of the car park status. Therefore, the control system will play a major role in organizing the entry to and exit from the parking lots. In some instances, it is also capable of being able to control multi-level parking lots which occupies less need on the ground and contains the large number of cars [3]. Therefore, the need of using technologies has become inevitable. In the modern world, where parking-space has become a very big 1
problem, it has become very important to avoid the wastage of space. This system allows real-time information to be accurately provided to motorists through Intelligent Parking Systems (IPS) to reduce congestion in or near parking areas, insufficient utilization of the available parking space stock, road congestion caused by space-searching traffic, access problems and safety hazards caused by illegal parking and environmental strains. With proper deployment of modern technologies in the parking areas, Time and Cost which are the two important factors of human life will be enhanced [4] 1.1.Programmable Logic Controller Programmable Logic Controller (PLC) is a microprocessor-based controller that uses a programmable memory to store instruction and implement functions such as logic, sequencing, timing, counting and arithmetic functions in order to control machines and processes. Logic is used because programming is primarily concerned with implementing logic and switching operations. The PLC takes signals from input device and control output devices with user defined program stored in its memory. PLCs offer a flexible programmable alternative to relay-based electrical circuits. The controller can be used for a wide range of control systems. Hence, there is no need for re-wiring, all that is needed is to key in different set of instructions. PLC consists of four major parts namely Input Module Output module Processor Power supply unit A PLC showing its component parts is shown below. Figure 1: Typical PLC The processor unit or central processing unit (CPU) is the unit containing the microprocessor. The main function of the microprocessor is to analyse data coming from field sensors/switches through input modules, make decisions based on the user s defined control program and return signal back through output modules to the field devices. The processor section makes the decisions needed by the PLC so that it can operate and communicate with other modules. It communicates along either a serial or parallel data-bus. The processor reads the physical input, scans the ladder logic program and writes 2
the physical output (update).the process of reading the status of the input and energizing or de-energizing the output according to user program is called Scanning while the time required to complete the process is the scan time. The input modules provide the interface between the PLC and the outside world, allowing for connections to be made to input devices such as switches and sensors. The output module transmits discrete or analog signals to activate various devices such as hydraulic actuators, solenoids, motors, and displays the status (through the use of LEDs) of the connected output points. The power supply unit is needed to convert the mains AC voltage to the low DC voltage (5V) necessary for the processor and the circuits in the input and output interface modules. The power supply (PS) section gets its input power from an external 240VAC source (line voltage), which is usually fused and fed through a control relay and filter external to the PS. In addition, the PS has its own integral AC input fuse. This line voltage is then stepped-down, rectified, filtered, regulated, voltage- and current-protected, and status-monitored, with status indication displayed on the front of the PS in the form of several LEDs (light-emitting diodes. The PS output provides power to every module in the PLC; however, it does not provide the DC voltages to the PLC's peripheral I/O devices. The block diagram showing the key components used in this work is shown in figure 2 below. PROXIMITY SENSORS LIMIT SWITCH PC PLC MOTOR Figure 2: Block diagram of key components 1.2.Research Objectives The aim of this work is: a) to design and simulate a car park control model with the aid of PLC using Ladder Logic programming, because it gives more structured approach rather than conventional approach. b) to develop an intelligent, user friendly automated car parking system which reduces cost, traffic congestion and fuel consumption on the vehicle. 1.3. Statement of Problems i. Improper Parking 3
In a conventional parking lot management system, a lot of improper parking are being witnessed despite the presence of a dedicated car park manager who is also regarded as a Gate Man because the cars in the parking lots are usually more than the required number and sometimes some car owners find it difficult to take out their cars because they have been blocked out of the way. To address this challenge, an automated car park system using PLC is being developed. ii. Cost Managing a car park is often times financially involving in terms of the over head, because at least two personnel will have to be employed to manage both the entry and exit points of the car park. With the deployment of intelligent system, a lot of funds are saved because the devices will be fixed. 2.0. Related Works Gongjun Yan et.al, (2011) describes a novel, secure, and intelligent parking system (Smart Parking) based on secured wireless network and sensor communication [5]. High parking space utilization and fast free spot finding time are the result of proposed research. Soh Chun Khang et.al, (2010) presents a parking system in which driver comes to know about the space availability in the parking lot with the help of SMS service. Driver can resend SMS in order to request new space if the previous one is filled. Driver can find nearest space for parking using wireless mobile based car parking system. Results, shows that the system efficiently allocates the slots and utilizes the full parking space [6]. Ankit Gupta et.al, (2010) describes an efficient car parking algorithm for ackerman steering configuration. This algorithm uses geometric calculations for path planning. Result shows a fast, efficient and safer parking system [7]. Hua- chun tan et.al, (2009) proposed an efficient car searching technique for larger parking lot. In this paper, cameras are installed in roads nearby parking lot and information regarding car like colour and license plate recognition is captured and saved in the database [8]. S. V. Srikanth et.al, (2009) proposed a parking system which eliminates problems regarding finding vacant slot for parking. Author uses wireless technology to enhance parking efficiency [9]. Gongjun Yan et.al, (2008) proposed NOTICE based parking system. In this parking system, drivers can check and reserve the slot for parking. For security purposes encryption/decryption techniques are used. Simulation results are highly efficient [10]. Insop Song et.al, (2006) proposed FPGA based parking system using fuzzy logic controller (FLC). Reduction in computation time is its advantage [11]. Bong, D.B.L et.al, (2006) discussed about car park occupancy Information system, using Matlab and cameras for finding free parking lots. In this work, images captured by a surveillance camera were processed in real-time to identify the occupancies of the parking lots. The paper further discussed that, occupancy information is further processed by a central control unit and distributed to display panels located at strategic locations at the parking area. The drivers can easily find a vacant parking lot based on the information displayed on the panels [12]. Rehanullah Khan et.al, (2013), talked about providing an interface and a software/ hardware module for Intelligent Car Park Management System (ICPMS) on FPGA. Here, the ICPMS will provide an extensive management for vehicles including parking facilities and security. In the work, ICPMS is validated using a test case scenario and extensive experimentation proves the feasibility of the approach [13]. Shuo-Yan et al. (2008) also proposed an intelligent agent system that helped in selecting the optimal price car park [14]. In all the papers reviewed in this work, facts have been delivered and contributions have been made to knowledge. However, emphasis are yet to be laid on the use of PLC to design and implement a secured Entry and Exit Car Parking Lot, which this paper seeks to carry out. 3.0. Materials and Methods 3.1. PLC and Software The PLC used in this work is Micro Logix 1000. It has 8 input and 8 output modules and has an interface for RS232 for connection to a PC. The programming software used is RSLOGIX 500 and the communication software is RS LINX 500. As earlier mentioned, the programming method used is the Ladder Logic diagram. However, there are other programming methods in PLC, which include; Sequential Function Charts, Structured Text and Function Block Diagram. Although, there are other programming languages used in PLC the Ladder Logic diagram has proved to be the most efficient of all. Several controllers such as Siemens, Omron, Mitsubishi and Allen Bradley are available in PLC, in this work; Allen 4
Bradley is the choice. The following figure gives the signal flow in a secured entry and exit gates of an automated parking lot. Input from proximity sensor Motor ON (Forward) INPUT FROM LIMIT SWITCH 1 MOTOR OFF TIMER TO START MOTOR IN REVERSE MOTOR START IN REVERSE INPUT FROM LIMIT SWITCH 2 Figure 3: The flow of control signal to automate entry and exit gates 5
4.0. Simulation and Results 6
Figure 4: Program for the operation of both Entry and Exit Gates 4.1. Discussion 4.1.1. Entry and Exit Process When a car approaches the gate and it is within a range of 10m from the gate, the proximity sensor detects the car and gives a high output. The high bit is given to the PLC which in turn gives a signal to motor; the motor windings are energized and rotate in a clockwise direction to open the gate. The gate continues to open even if the car has moved out of the 10m distance range from the gate. The motor continues to rotate in that direction until the gate closes limit switch 1 placed at its extreme. The high bit of limit switch 1 stops the motor and also activates a timer for 10secs.The type of timer used is an On-delay type and it s inbuilt in the PLC. When the timer timing finishes, its done bit is high; and this is used to activate the motor windings but in reverse direction to close the gate. The motor rotates in this reverse direction until the gate it drives closes limit switch 2 (giving it a high output).this high bit is used to stop the motor movement, here the gate is fully closed. As the gate is closing, if another car approaches the gate and the car moves within a range of 10m from the gate, the high bit, which sensor 1 now has, is used to halt the gate closing process and opens the gate again. In order to control/monitor and restrict the number of cars in the park to 100(park capacity), the system is equipped with photo sensors to count the number of cars entering and leaving the park. A pair of sensor is placed at the entry gate and another pair at the exit. The sensors at the gate entrance increment an up-counter (programmed in the PLC) when a car enters and those at the exit side decrement a down-counter when a car leaves the lot. When the counter Accumulator equals its Preset (set at 100, the lot capacity), the Done bit of the counter is high. The high bit is used to put on a light indicator that indicates PARK FULL. At this point, the park capacity is reached and the gate is not opened even when sensor 1 output is high. 5.0. Conclusion and Recommendation Parking becomes easy, cost effective and ultimately results in pollution free society using the designed system. The system can be used for many other applications and can easily be enhanced to accommodate more than 100 cars captured in this work. Therefore, modern technology such as the PLC should be deployed for effective car park management system. 7
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