1.
INTRODUCTION
The modern sensing technology and control methods are undergoing
continuous innovation, where the real-time temperature control is demanding
higher accuracy and faster response more than ever. Temperature control is
widely used in production and industrial control processes in all aspects. For
example, in the iron and steel smelting process, iron and steel to be baked
requires heat treatment in order to achieve their performance indicators;
plastic qualitative process also needs to maintain a certain temperature range.
The fact is that the temperature control system is a complex process object
involving large inertia and pure delay with multi-variable and time-varying
parameters. At present, the PID control methodology is adopted in most
cases. In this way, different PID parameters should be selected for different
control objects, for which some practical experience is needed.
2.Temperature Control using Siemens PLC Lab
The purpose of this lab is to control the water temperature by using
temperature sensor and heat actuator. The lab is continuation of interfacing
analogy inputs explained in lab 2 and 3, and how they can be used to control
the system using a set temperature. The designed system can be used to
control air-condition (AC) temperature, smart kettle, boilers, home heating
systems etc.
2.1 Description of Functions
2.1.1 Brief Description
The heating pan (see Figure 2.1) is used to heat water to a set temperature.
The set temperature is entered manually using a control panel interface.
Inside the pan, a temperature sensor is placed which will be used to monitor
if the water temperature reached the set value. If the water temperature in
below the set temperature the heater is actuated until it reaches the
maximum value. At the maximum value the heater should stop and allow
water to cool to minimum value. The control will proceed as long as the
system is on. The values can be displayed on the control panel as in Figure
2.2 – 2.4
2.1.2 Technology diagrams
L
N
VCC
DATA
GND
T = Temperature Sensor
T
Coil
Water
Heating Pan
Figure 4.1. Heating Pan
WATERTEMPERATURECONTROL
CHECK
SETTEMPERATU
PERFORMAN
RE
CE
32.1OC
CURRENT
TEMPERATURE
VALUE
ON OFF HIGH
Figure2.2 Control Panel – Home Screen (Buttons not Active)
WATERTEMPERATURECONTROL
CHECK
SETTEMPERATU
PERFORMAN
RE
CE
32.1OC
CURRENT
TEMPERATURE
VALUE
HIGH
LOW
ON OFF
Figure 2.4 Control Panel – Home Screen (Active buttons)
SET TEMPE RATURE WIND OW
SET TEMPE RATURE BACK
30.0 C O
SAVE
Figure 2.2 Control Panel – Set Temperature Screen
2.1.3 Switching ON
The station is switched on with the main switch Q0. Relay K0 (main switch
"ON") is energized and provides the supply voltage for the sensors and
actuators. This operating state is indicated by indicator light P1 (main switch
on)
2.1.4 Emergency Stop
In the absence of feedback from the EMERGENCY STOP (A1), all drives must
be stopped immediately. When feedback from the EMERGENCY STOP function
is present again, the station may only start up again after another start signal.
Activation of the EMERGENCY STOP is indicated by indicator lights P4
(EMERGENCY STOP activated).
2.1.5 Temperature Control
If the temperature sensor detects the temperature below 10% of the set
temperature, the coil actuator is activate. The water is heater until maximum
value of temperature (above 10% of set temperature), at this point the
actuator is deenergized allowing the water to cool. The process continues as
long as the system is on, when the set temperature is changed the system
should follow a new set temperature.
2.1.6 Indicator Lights
As soon as relay K0 (main switch "ON") becomes energized, indicator light P1
(main switch on) lights up.
If the EMERGENCY STOP function has tripped, P4 (EMERGENCY STOP
activated) lights up.
Indicator light P6 (Coil ON) lights up as soon as the coil actuator is activated.
2.2 Reference List
2.2.1 Inputs (DI)
Name Type Address Function NC/NO
-A1 BOOL %I0.0 Return signal emergency stop ok NC
-K0 BOOL %I0.1 Main switch “ON“ NO
-S1 BOOL %I0.2 Pushbutton ON NO
-S2 BOOL %I0.3 Pushbutton OFF NC
2.2.2 Inputs (AI)
Nam Type Address Function
e
-A1 REAL %W64 Temperature Sensor Input
2.2.3 Outputs (DO)
Nam Type Address Function
e
-Q1 BOOL %Q0.0 Coil Actuator ON
-P1 BOOL %Q0.3 Display “main switch on“
-P4 BOOL %Q0.4 Display “emergency stop activated“
-P6 BOOL %Q0.6 Display Heater Coil -C “ON“
Legend for reference list
DO - Digital Output AO - Analog Output Q – Output
DI - Digital Input AI - Analog Input I - Input
NC - Normally Closed NO - Normally Open
2.3 Description of components of the station
2.3.1 General Operation
2.3.1.1 Push Buttons
The utilized pushbuttons can supply either a "0" or "1" signal. Depending on
whether you have planned them as normally-closed or normally-open
contacts (see Reference list), they supply a "1" or "0" signal when not
actuated. The signal changes to "0" or "1" only while the pushbutton is being
pressed.
2.3.1.2 Switches
The utilized switches can also supply either a "0" or "1" signal. Depending on
whether you have planned them as normally-closed or normally-open
contacts (see Reference list), they supply a "1" or "0" signal when not
actuated. The signal changes to "0" or "1" when the switch is actuated. This
signal is present as long as the switch is not actuated again.
2.3.1.3 Feedback from Emergency Stop Pushbutton
EMERGENCY STOP pushbuttons are pushbuttons with an additional
mechanical lock and are connected to a safety relay. They thus behave like a
switch. The EMERGENCY STOP feedback from the safety relay is planned as a
normally closed contact for safety reasons. If a wire break occurs, therefore,
this feedback is no longer present and the station responds as if an
EMERGENCY STOP has tripped.
2.3.2 Sensors
2.3.2.1 Temperature Sensor
In this case the potentiometer (variable resistor) is used to simulate the
behaviour of temperature sensor.
2.3.3 Actuators
2.3.3.1 Heating Coil Contactor
The contactor allows the heating coil to be energized which requires signal "1"
at Q1 "Coil Actuator (C) ON"
2.3.3.2 Indicators
All indicator lights are located on the control panel and which are not
indicated should be hardwired on Vero board. If signal "1" is present, these
indicator lights illuminate.
2.4 Components and Devices
SIMATIC S7 1200 PLC, Profinet Cable, LM 35 temperature sensor, Water resist
material, Resistors, Capacitors, Engineering Station, Analog Output SB1232,
OPAMP APA363, ANA122 instrumentation amplifier, Heating Pan, Contactor
(24VDC to 220VAC), Heating Coil, Water and SIMATIC HMI KTP700 BASIC.
2.5 Task
1. You are required to design the temperature control system using the
given Siemens TIA Portal V14 using any available PLC language. The
program should be used to program Siemens S7 1200 PLC.
2. Design SIMATIC HMI program for Control panel display as shown in Fig
2.2 – 2.4.
3. Simulate the system
Hard-wire the temperature control system using provided materials.
