1. 1
PLC BASED CONTROL OF HEAT EXCHANGER
Abinash Kumar Panda1, Fijo M. Francis2, Sudha R3
1School of Electrical Engineering Vellore Institute of Technology
2School of Electrical Engineering Vellore Institute of Technology
3Professor, School of Electrical Engineering Vellore Institute of Technology
In this paper transfer function of a heat exchanger is implemented in MATLAB and is controlled by a PID controller.The
controller is implemented in PLC(S7-1200) . They both are interfaced using Arduino. The advantage of this method is that without
having the actual plant, its response can be studied if the transfer function of a system is available. We have used Arduino Uno
for interfacing PLC with MATLAB.The response of the system for three set points were noted.This project also shows that even
though Arduino can be used for interfacing it has certain limitations.
Index Terms—heat exchanger, Programmable Logic Controller (PLC), Proportional-integral-derivative (PID) Controller, Arduino
Atmega 2560
I. INTRODUCTION
Usually we do different type of response analysis in MAT-
LAB using Simulink and command window but real time
control is not possible in these type of implementation. We
just get a glimpse of what the system is like whether the
system or plant is stable or unstable but the real response of
the system cannot be known. We can change the set point and
see what happens in real time which is not usually possible in
Matlab and Simulink packages. That will only be known when
the system is actually being controlled by a PID controller.
Here the MATLAB will behave like an actual plant and the
controller will control the developed plant in MATLAB in
real time so that we will be able to analyze what actually is
happening in between the plant and the controller. In this way
we are developing a new method to check the response of a
real time plant control without having the actual plant with
us. To make the plant to interact with the controller we have
to take an interfacing device which will create the behavior
of the plant inside it. The interfacing device can be controlled
with PLC.
Arduino Uno is a microcontroller which is based on AT-
mega328P. It has 6 analog input pins, 14 digital input and
output pins. Out of these 14 pins 6 pins can be used as PWM
(pulse width modulated) output pins. It Uno uses 16 MHz
quartz crystal. It also has an ICSP header and a button for
reset.
PLC contains three important parts, they are Power supply,
CPU, input output modules. The input output modules can be
divided into analog and digital. Here in this paper we have
used both analog as well as digital. We have taken our set
point as a digital signal. And we have also used pulse width
modulation for giving the output signal. The range of input
signal is usually 0 to 24 volts and the range of output signal
is in between 0 to 12 volts. Which is also the range of arduino
input voltage range so this is the reason why we are able to
interface both device.
The selected heat exchanger is used in the recovery of soda in
.
a paper pulp industry. In paper industry chemicals are used to
separate cellulose from wood and other substances used for the
production of paper. After doing this we need to recover these
chemicals for the economical operation of the plant. So the
resultant product is burned to produce heat, which is used to
produce steam and and run the turbine to produce electricity.
We in this paper has taken the heat exchanger used in this
process for doing our real time control using S7-1200 PLC.
II. METHODOLOGY
Heat Exchanger model is taken from our reference paper
[4]. This plant model we have implemented in MATLAB.
The transfer function of heat exchanger gives the relationship
between fluid entering into the heat exchanger and the tem-
perature of the fluid coming out of the heat exchanger of the
other side. This process of fluid inflow into the heat exchanger
is usually controlled by the valves ,what PLC will do is that
,it will control that valve by giving the required amount of
voltage which is usually a control signal output from PLC.
Transfer function of heat exchanger is given below :
Gp(S) = 34/(30s + 1) (1)
Transfer function of the control valve
Gt(S) = 1.25/(3s + 1) (2)
Transfer function of the temperature sensor is
Gt(S) = 0.08/(2s + 1) (3)
Hardwares required for this research project are:
1) PC
2) Arduino Uno
3) PLC S7-1200.
softwares used are:

2. 2
1) MATLAB 2015b
2) Arduino Software
3) TIA V13. [5][6]
The whole process is described in steps given below
Step-1:The plant, feedback sensor and actuator transfer
function is made available in simulink through the transfer
function block.Arduino and Matlab arre connected through
the Arduino Simulink support package.[7]
Step-2:The PLC is programmed by using Total Integrated
Automation (TIA V13) software.It is this program which
drives the PLC S7-1200.
Step-3:The PID controller is designed in the PLC cyclic
block.
Step-4: All the input output ports which are needed for the
PLC to communicate with Arduino are defined.
Step-5: Finally both Matlab and Arduino are interfaced
through the ports defined for this purpose.
Fig. 1. Block diagram for control operation
The output signal is pulse width modulated(PWM) and it is
given to the Ardunio via its analog input port.
III. DESIGN
The transfer function of the plant is implemented in
Simulink.The input to the plant is given by analog input
block of Simulink and the output of this plant is given
to Arduino by the analog out block of Simulink. The PID
controller is designed in PLC software as given Figure (4). The
PID controller can only be implemented in the cyclic block
present in PLC. As this is a real time implementation the time
constraints here are very important. The controller should react
to the process within a specified amount of time otherwise the
process cannot be controlled in the desired manner. In this way
our method is different from other models. The tunning system
given inside the PLC was used for tunning the PID. There
are two types of tuning system inside PLC out of which fine
tuning mode was implemented. The sampling time was taken
to be 0.001 seconds.By implementing the above mentioned
methods the PID control was implemented.Different types of
control outputs were got which are shown in the figures. Three
different set points were taken and the graghs were noted
down.
Fig. 2. Plant model implemented in Matlab
Fig. 3. PID parameters got after fine tuning the PID.
Fig. 4. PID Controller model implemented in PLC
Fig. 5. Plot of control output of plc,set point and process variable for a set
point of 45 degree for time in between 0-460sec.( blue line- set point,green
line heat exchanger temp.,red line is the controller output.)
Fig. 6. Plot of control output of plc,set point and process variable for a set
point of 40 degree.

3. 3
Fig. 7. Block diagram for control operation
Fig. 8. Block diagram for control operation
IV. RESULT AND CONCLUSION
1) It is observed that as input increases from the set point,
the controller output decreases proportionally and vice-
versa.
2) It takes some time for the system to auto tune itself.
3) Arduino maximum possible output voltage is 5v.This
limits the temperature range over which we can do the
analysis.
REFERENCES
[1] [1] PID implementation of heating tank in mini automation plant using
Programmable Logic Controller (PLC)-Reza Ezuan Samin -June 2011 In-
ternational Conference on Electrical, Control and Computer Engineering
(INECCE), 2011
[2] PLC Based PID Speed Control System-Avinash P. Kaldate 1, Sachin
A. Kulkarni -IOSR Journal of Engineering (IOSRJEN) ,March 2014.
[3] Design and Implementation of PID Controller in Programmable Logic
Controller for DC Motor Position Control of the Conveyor System-
Muhammad Sharfi Najib, Mohd Shawal Jadin, Raja M. Taufika Raja
Ismail, Mohd Rusllim Mohamed- 3rd WSEAS/IASME International Con-
ference on Dynamical Systems and Control, Arcachon, France, October
13-15, 2007
[4]Modeling and Simulation of Heat Exchanger Used in Soda Recovery-
Chhaya Sharma, Sanjeev Gupta, Vipin Kumar - WCE 2011, July 6 - 8,
2011, London, U.K.
[5]https://www.arduino.cc/en/Guide/HomePage
[6]http://w3.siemens.com/mcms/programmable-logic-
controller/en/basic-controller/s7-1200/Pages/Default.aspx
[7]http://in.mathworks.com/hardware-support/arduino-matlab.html