PLC Automatic Railway Gate Control System Conference Paper

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PLC based Automatic Railway Gate Control System
Conference Paper · June 2010
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Muhibul Haque Bhuyan
American International University-Bangladesh
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Tr' Conference on Electronics ancl Telecommunication 2010
Bangladesh Electronic Society
PLC based Automatic Railway Gate control system
'M,rhibul Haque Bhuyan- and 2Md. Ahsanol Kabir
' Deportrr"rt of Electrical and Computer Engineering, Azintur Rahntan Sclrcol of Ertgileering, presi1errcy lJlive rsittt
' 2Depo,tn,,,r of Etectronic, o,ara,,l0*5i,liJl,'li'#,!illif;ritr:;:rirw,#:,:,o,u,r"*,ur, ,0, ,njo,,.*,*, o,,**
Abstract
At present, railway crossing gate control system in, Bangladesh is being operated manuaily. Thus many acciclents are being
occuned if it is not done in proper time. so, it needs to b. urtomuted tJreduce accidents. in this wor.k, an automatic railway
crossing gate control system has been developed using.a Programmable Logic Controller (pLC). For this purpose, we used Allen-
Bradley Micrologix PLC and Rockwell software foiPLC f,rogramming. Signaling light models are implemented usin-e sever.al
red, green and yellow Light Emitting Diodes (LEDs; ana raitriay gut.."are op..ated using DC motors with gear trains rhar are
connected to the output ports of the PLC. For energizing differeit parts of the system and DC motor.s, separate DC power
supplies have been designed. It is found that rhe implementid ,yrt.- *o.t, very well.
Key words: PLC, LED, automatic railway gate control, DC motor.
I. Introduction
Programmable Logic Controller (PLC) has become the most powerful change to occur in the electronics world for.
factory automation tll' This is well suited to the cyclical and repetitive operations [2]. Unless a system
reconfiguration is required, the functions executed uy a nI-c are fixed, the prolrams need not be changed and
therefore, rhey may be srored in a programmable Read only Memory (pRoM) i3-4'j.
Automotive technologies are gaining importance in modern day traffic control systems, since the number of road
vehicles and passengers is-rapidly growing. In every modern city, there are several railways that cross the r.oad ancl
hence road traffic is halted for few minutei when train crosses tr,e .oaa. Hence, there is a perpetual need tbr saf-ety-
critical railway gate control automation. The main goal of engineering is the planning and management of trafflc
control systems [5]' Few works are found in the litei'ature on tiaffic control system based on microcontroller, pLC
and LAN [6-8]' It is now the time to address the automation issue of railway gate crossing. In t9l, a work is found
on automatic railway gate control using the RF technology. But it has the p.oui"-, of implofer automatic detection
and huge cost of implementation. Because, the behavioi of this kind of control system is lilu"ncea by two main
factors: the control inputs and the disturbances incurred. The control inputs are dirlctly related to the co*esponding
control devices such as sensor, motor and variable message signs. ih" manipulation of disturbance values is not
possible' but in some cases they are measurable (e.g. a"Ir"unil, detectable (e.g. incident) or predictable over a
certain time horizon' The most challenging issues relate to automatic incident detection, the modeling of
uncertainties, providing a solution that offers robustness under external disturbances, the use or variable message
signs in order to avoid traffic jams, human life safety and finding an optimal itinerary [5].
Therefore' in this work, we have developed a PLC based automatic railway gate control system. Because, pLC has
many advantages over microcontroller or radio frequency, such as, graphicniode p.ogru,n,,irg, noise immune, less
hardware connections, easy do-wnloading of program, rister acting"etc. ttre ,yr,". i, a"".r"p"o for a junction of
rail crossing with road traffic. Signaling light models are implemenied using LEDs of different colors, because LED
lights are chip' light up very quicklyinJ corrr-e very ltw power [l0f Railway guo, u." operared using DC
motors and gear trains' Besides, different sensors are used to "nrrr" proper operation of the gate. It is found that the
implemented system works very well.
II. Basic PLC Architecture
A Programmable Logic controller (PLC) is a solid-state device, designed to operate in noisy industr.ial
environments and perform all the logic functions previously achieved uiing electro-mechanicai relays, drum
switches' mechanical timers and counters' The structure of a PLC is that of a computer, it consists of a centrrl
Processing Unit (CPU), a memory, input/output modules and an internal bus. A pLC receives input signals (as
command input) from process equipment to be controlled, such as, switches, sensors etc., processes them according
to a precise model defined by the programs and provides output signals to the process equipment, such as, relays,
motor' starters etc' The. e]-c 1s usually programmed with iangua'ges conforming to IEC-I131 standard and is
conceived to work in an industrial environmeni. A block diagram lr tte plc architecture is shown in Fis. 1 .
136

Conference on Electronics ancl Telecorlmunication 2010
Bangladesh Electronic Society
The input devices that are sensors monitor the machine or the process being controlred. The status of these sensors
(oN or oFF) is fed to the PLC controll"i to ,"na the signals t"'rrii"ir on tJr".Jir"j'". ,rlo,, off (de-energ ize) the
output devices (motors, relays, valves etc) in order to coitror rt" rnu"r,in" or process [3].
III. System Block Diagram
The system block diagram and its implementation are shown in Fig. 2. To imprement this project, we need an IBM
PC installed with software in windows environment, A^lten-Bradr"v uti-r-"!;;ffii;irii'J".,", c pLC processor,
resistors' LEDs of three different colors to make traffic sign;isi1 ,oua. and railway, DC motors and associare
circuits to actuate the railway gate, va.ious-i"rro^ to sense whether the train has passed it" !or" or not and whether
tbe gate has opened or closed, "orn""ting *i."r, "^t".nul DC power supplies etc. J
IBM PC is used to write' edit' compile' debug.and-then finally to download the program in to the pLC processor.
The PC's serial port (coMl) it .orr".i"Jio ,rr" prc', orN ro.t"t uy u 9 pi; ,;;i;'r"nr".., t,l. At that rime,
the PLC must be in PRoG mode [3]' art"t ao*,toaaing tr,e pffili tq is no Ionger required. Then the pLC is set
in RUN rnode to send the output tig'"rti" ilJ ourpu, ports. LEDi, used in signaring system, are connected with the
output ports of the PLC via resistors and DC o.9.*"; ;;eer). "sipl*t" oc;"r;; ;'rppil;r' are designed using a
reguJated power supply rc'LM3l7 [12] anJrecirier modutes r"rligr"rirg sysrems, ,"nro* and DC morors. Gear
trarns are used to reduce the speed of the railway gate atproper tevit. r'oir il;ir;;;"u." ur"d her.e. one set
senses the train when it comes near the junction, then the second ,erro. set ensures the proper closing of the gate
when the red signal of the traffic lishr of i[;;;ad becomes ,r.r"Jbri.'rn"n;; il;;r;;"r;:::rr", whether the tr.ain
has passed the railway crossing "oi,pt"t.ty una finally th" f;;;il irro, ,"nr", rhe complete opening of the rairway
gate' From this last sensed signal, *," grl; iranic iight of th" ;;;'becomes *rr"J 6ri. according to the plc
programming' the whole railway gate -control signals and r;;r;;;r" operared in definite sequence. Erectro,ic
actuator and sensor circuits have also been designed and tested rlir
ii
Input Devices Output Devices
Machine or process being controlled
Fig. 1 Basic pLC architecture
-ED Array of Traffic
Light Signals for
Road and Railwav +
Sensors of Rail Line
and Rail Gate
Fig' 2 Hardware brock diagram of the railway gate contror system and its implementation

Conference on Electronics and Telecommunication 2010
Bangladesh Electronic Society
IV. Software Development
In PLC programming, two Rockwell Softwares have been used. One is programming software, RSLogix that is used
to write, edit, compile, debug and download the program to the PLC. The other is communication softwale, RSLilx
that is used to send the binary data from the PC to the PLC processor by establishing a duplex data transfer protocol
at a baud rate of 19200 with BCC error checking code [3].
To develop the PLC program, two basic PLC programming instructions are used, such as, examine on ancl output
ener gize instructi ons.
The examine on instruction represents the input condition. It tells the processor in the PLC to examine an input at an
address specified by the instruction. The specified address may either be internal or external to the PLC.
The output energize instruction sets an output address, specified by the instruction, true only when a set of input
instructions preceding it in a rung produce a path of logical continuity and vice-versa. The address may be either.
external to the PLC processor or internal. When this instruction is true, the corresponding external output device is
energized, or the logic bit at the specified address is set to I and vice-versa.
Here4 input and 4 output instructions are used. In the l't rung, input switch get input from sensor I and output will
actuate the DC motor in forward direction to close the railway gate. In the 2nd rung, input switch will get input fi.om
sensor 2 and gives an output signal to green and red LED lights. Rung 3 and 4 gets inputs from sensor 3 and 4 and
gives signals to output red and green LEDs and also DC motor to drive it in reverse direction so that the railway gate
is opened'completely. After testing the whole system it was found that the system works satisfactorily. The
advantages of using the PLC is that if same PLC is used for several railway crossings for controlling the railway
gates of a particular rail line then the signaling system will automatically be synchronized, no additional
synchronizing equipment are needed and hence prior alarming signals can be generated to reduce the accidents.
Thus an automated railway gate control signaling system can be developed.
V. Conclusions
Now a day, PLCs are being used to reduce maintenance and labor cost of many control systems solutions. Within
next five to ten years many existing control systems will be replaced by PLCs. Therefore, it is highly recommended
that a complex system like railway gate controlling will be based on PLCs. In this project, we have developed such a
control system. A prototype road and rail line model with railway gate has been created ancl implemented in the
laboratory. After successful laboratory testing of the whole system, it was found that the developed system operates
satisfactorily.
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