Low cost Wireless I/O’s using PLC, HMI & ZIGBEE


Low cost
Wireless I/O’s using PLC, HMI & ZIGBEE



Abstract— During the past decade, the industrial sector
throughout the world has shifted from the classical methods of Control and
Automation to the state of the art techniques. This allowed the industries to
attain a higher percentage of growth and production, which consequently gave
rise to reduction in costs of the products. This trend of automation is gaining
popularity at a very slow pace due to huge initial costs associated with it. This
problem can be addressed by promoting Wireless I/O’s interfaced to Programmable
Logic Controllers using Zigbee, which might encourage the industries to take
the path of modern automation.
KeywordsWireless I/O’s, PLC, HMI, ZIGBEE Automation
System
.
I.     
Introduction
PLC’s
are solid state devices using integrated circuits to control process or
machines.  They  can 
store instructions  like  sequencing 
counting,  timing,
arithmetic,  data  manipulation 
and  communication [7]. A PLC is
an example of a hard real time system since output results must be produced in
response to input conditions within 
a  bounded  time, 
otherwise unintended  operation  will 
result.PLC
  reads  the status 
of  the  external 
input  devices,  e.g. 
Keypad,  sensor, switch  and 
pulses,  and  execute 
by  the microprocessor  logic, 
sequential,  timing,  counting and arithmetic operations according
the status of the input  signals  as 
well  as  the 
pre-written  program stored
in  the PLC  [8]. The generated output signals are sent
to  output  devices 
as  the  switch 
of  a  relay electromagnetic  valve, 
motor  drive,  control 
of a machine or operation of a procedure for the purpose of machine
automation or processing procedure.
Zigbee falls in the category of wireless domain like GSM and RF
technology. Zigbee provides the wireless communication. It means Zigbee only
reduces the cost and maintenance of the wires used for connections else all the
process will be  same  such as Zigbee will provide a particular bit
on/off  status  to  the
other  side due  to which 
same message  or  data 
we  can  get 
on  the  other 
side  as  wire 
provides.  Thus Zigbee replaces
the connecting wires and provides a wireless communication [1].
As the wireless PLCs use modem for transmitting signals from PLC to the
process here we are using Zigbee as the communication interface which is used
for transmitting and receiving the signals from the PLC to3 process and
vice-versa. Zigbee is a wireless technology developed as an open global
standard to address the unique needs of low-cost and low-power wireless
personal area networks (WPANs). The Zigbee standard takes full advantage of the
IEEE 802.15.4
II.  
Method of Interfacing
PLC and SCADA/HMI placed at control room and consists of PLC input and
output Module and a TARANG Zigbee for receiving and transferring signal.

Figure 1 Block Diagram
TARANG Zigbee
acts as transreceiver. A pair of TARANG Zigbee transmitter and receiver is used
where wireless exchange of data takes place and hence two way communication is
done. The application “Monitoring” takes place at the field/process site. It is
placed in a remote area and consists of sensors and actuators [1].
The
process controlled in the project using a PLC is a Batch process used to
manufacture a chemical and the parameters to be controlled and measured is
level.



Some applications
require specific quantities of raw materials be combined in specific ways for
particular durations to produce an intermediate or end result. A batch process
performs list of actions in a sequence. It executes a series of non-interactive
actions all at one time. Once a batch job begins, it continues until it is
done. One example is the production of adhesives and glues, which normally
require the mixing of raw materials in a heated vessel for a period of time to
form a quantity of end product. Other important examples are the production of
food, beverages and medicine. Batch processes are generally used to produce a
relatively low to intermediate quantity of product per year (a few pounds to
millions of pounds).

Benefits of Batch
Process
·     A batch
process can be used to automate much of the work.
·     Batch
processing can save time and energy by automating repetitive tasks.
·     Batch
time can be adjusted to meet quality specs
·     Slow
dynamics permit real-time calculations
Batch
process component-
·     Process
Tank 1(for mixing the two liquids in proportion)
·     UNIT Tank
1 (containing liquid A)
·     UNIT Tank
2(containing liquid B)
·     Stirrer
·     Solenoid
Valve 1
·     Solenoid
Valve 2
·     Solenoid
Valve 2
·     High
Level Float Switches
The BATCH
PROCESS setup is placed in a remote area (field/process site) and is controlled
from the control room wirelessly using TARANG Zigbee where PLC, SCADA and the
control panel are placed. The process is controlled through SCADA&PLC in
auto mode and can also be controlled in manual mode. The process can be
controlled and monitored directly from SCADA and also from the control panel.
            The main components are
TARANG Zigbee and PLC which control the whole process.The TARANG is used as the
source and which is used in direct mode.PLC is used to control and monitor the
batch process. [1]



III.
 TARANG ZigBee
TRANG modules are designed with low to medium transmit
power and for high reliability wireless networks. The modules require minimal
power and provide reliable delivery of data between devices. The interfaces
provided with the module help to directly fit into many industrial
applications. The modules operate
within the ISM 2.4-2.4835 GHz frequency band with IEEE 802.15.4
baseband. [3]
IV.
Role of TMFT software
TMFT
Software is used to configure the TARANG Zigbee via RS -232 or USB cable. [5]
Module
Programming:
Step1:
Open TMFT Software
Step2:
Connect the TARANG module to the Serial/USB      Port.
Step3:
Choose the appropriate Port and serial parameters in terminal software&
press query modem.
 
Step 4:
For setting I/O pins as input and output the following steps should be
followed-
Step 5:
Enter the command mode with ‘+++’
Response
from modem should be ok.
Step 6:
Enable the desired I/O pin as input with command ATIDxx. In this example first
I/O line ID0 is used. For configuring it to Digital I/O input, send command as
ATID02. Response from module should be ‘OK’.
Step 7: Write these
parameters to memory with ‘ATGWR’ command.
Step 8:
Follow the same steps for configuring I/O pins to INPUT.
Step 9:
Exit command mode with ‘ATGEX’ command.
Note: Once I/O pins are configured
to input their default status Will be logic high (3.3V).
Step 10:
Enable the desired I/O pin as input with command ATIDxx. In this example first
I/O line ID0 is used. For configuring it to Digital I/O input, send command as
ATID40. Response from module should be ‘OK’.



V.   
 DESIGN AND IMPLEMENTATION
The
PLCs provide analog and digital series input/output that can be used to control
the field devices. For the PLC to be made to control data wirelessly, a
wireless interface is needed. The messages from the controller are sent to PLCs
through the RF transceivers. Thus, two RF transceiver circuits have to be
developed such that they are able to communicate with each other as Process
Side & Control Side.
 PROCESS SIDE:
The
figure 6 shows process side hardware. The components used on process side
consist of three tanks, Zigbee, Solenoid valve, Float switch and relay card.
The Zigbee receives the data & control the process. The circuit diagram or wiring
diagram is given below




Figure 5 Process Side Hardware

 CONTROL SIDE:
The above figure shows the control panel which controls the field or
process site. The main components are TARANG Zigbee and PLC which control the
whole process. The TARANG is used as the source and which is used in direct
mode.PLC is used to control and monitor the batch process. The circuit diagram
or wiring diagram is given below
VI.
 WORKING-
When the START button is pressed by the user batch process starts. Then
according to control algorithm written in PLC, the control signals from output
module of the controller is given to TARANG Zigbee ‘A’, which acts as a
transmitter. The first solenoid valve 1 is ON for time set in HMI screen from
UNIT TANK 1 and then solenoid valve 2 is on from UNIT TANK 2. Simultaneously if
PROCESS tank becomes overflow then either solenoid valve 1 or solenoid valve 2
is off and avoid overflow condition. After this agitator is on which mix the
two liquids uniformly. As soon as agitator is off we get uniform mixed liquid
and solenoid valve 3 is on and we get the output. At this operation TARANG Zigbee
on process side acts as a receiver and TARANG Zigbee on control side acts as a
transmitter
Now if the tank level of UNIT TANK 1, UNIT TANK 2 or PROCESS tank
becomes high the signal is received by Zigbee on process side and sends this
signal to control side Zigbee which monitor on input section of PLC and SCADA.
At this operation TARANG Zigbee on control side acts as a receiver and TARANG Zigbee
on process acts as a transmitter.
 
VII.            
HMI



HMI stands for Human Machine
Interface. It is not a full control system, but rather focuses on the
supervisory level. As such, it is a purely hardware package that is positioned
on top of hardware to which it is interfaced, in general via Programmable Logic
Controllers (PLCs), or other commercial hardware modules.[6]




It is a
small scale control system for automated industrial processes like municipal
water supplies, power generation, steel manufacturing etc.

HMI systems monitor and control these operations by gathering data from
sensors at the facility or remote station and then sending it to a central
computer system that manages the operations using this information.
The above figure shows the main MENU screen of HMI. By using
this operator can select the mode of operation like auto mode or manual modem,
we can check the status of overall process, by using setting we can set the
timer for solenoid valve for on and off operation. By using I/O list we can
check the status of input and output. Alarm is used for displaying overflow condition
.
VIII.          
 Conclusion
Batch Process is a very important and a widely used process in today’s
Industries. This is an effort to eliminate the use of cables for transmission
and overcome a major drawback in a mini setup. We achieve the task of
monitoring as well as controlling the Batch Process from a remote location via
a control panel, PLC program as well as HMI. The parameter controlled in a
closed loop process is Level
.
We have used TARANG Zigbee to transmit signals wirelessly between the
Control room and the Process.
References
[1]   
Kaushik
Bhuiya, Kintali Anish, “Low cost wireless control and monitoring using      PLC and SCADA”,International Journal of
Scientific and Research Publications, Volume 
Issue 9, September 2013 ISSN 2250-3153
[2]   
Programmable
Logic Controller Instruction Sheet by DELTA.
[3]   
www.melangesystems.com
[4]   
S.S.Bidwai,
V.B.Kumbhar. “Real Time Automated Control using PLC-VB Communication”
International Journal of Engineering Research and Applications (IJERA) Vol. 3,
Issue 3, pp.658-661 (Jun 2013).
[5]   
TMFT 2.6
test utility and configuration software manual.
[6]   
DELTA PLC Manual,” Delta Electronics
Inc,www.delta.com.tw/industrialautomation.
[7]   
T.Kalaiselvi,  R.Praveena 
,Aakanksha.R,, Dhanya.S,  PLC 
Based  Automatic  Bottle Filling  and 
Capping  System  With 
User Defined  Volume  Selection
,”  IJETAE.,     Volume 2, Issue 8, (August 2012).
[8]   
T.Kalaiselvi,  R.Praveena 
,Aakanksha.R,, Dhanya.S,  PLC 
Based  Automatic  Bottle Filling  and 
Capping  System  With 
User Defined  Volume  Selection
,”  IJETAE.,     Volume 2, Issue 8, (August 2012).

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