1.

PLC SIEMENS S7-1200

The S7-1200 controller provides the flexibility and power to control a wide variety of devices in

support of your automation needs. The compact design, flexible configuration, and powerful

instruction set combine to make the S7-1200 a perfect solution for controlling a wide variety of

applications. The CPU combines a microprocessor, an integrated power supply, input and output

circuits, built-in PROFINET, high-speed motion control I/O, and on-board analog inputs in a

compact housing to create a powerful controller. After you download your program, the CPU

contains the logic required to monitor and control the devices in your application. The CPU

monitors the inputs and changes the outputs according to the logic of your user program, which

can include Boolean logic, counting, timing, complex math operations, and communications with

other intelligent devices. The CPU provides a PROFINET port for communication over a PROFINET

network. Additional modules are available for communicating over PROFIBUS, GPRS, RS485,

RS232, IEC, DNP3, and WDC networks.

The CPU supports the following types of code blocks that allow you to create an efficient structure

for your user program:

● Organization blocks (OBs) define the structure of the program. Some OBs have predefined

behavior and start events, but you can also create OBs with custom start events .

● Functions (FCs) and function blocks (FBs) contain the program code that corresponds to specific

tasks or combinations of parameters. Each FC or FB provides a set of input and output parameters

for sharing data with the calling block. An FB also uses an associated data block (called an instance

DB) to maintain state of values between execution that can be used by other blocks in the

program.

● Data blocks (DBs) store data that can be used by the program blocks. The size of the user

program, data, and configuration is limited by the available load memory and work memory in the

CPU . There is no specific limit to the number of each individual OB, FC, FB and DB block. However,

the total number of blocks is limited to 1024.

1.2 LADING PROGRAMMING LANGUAGE KOP

Is a graphic language that allows you to represent the program in the form of electrical circuits.

Circuit elements, such as normally closed and normally open contacts and coils are connected

together to form segments (or "networks"). To create the logic for complex operations,

branches can be inserted to create parallel circuits. The parallel branches can be opened

downwards or connected directly to the supply bar and close upwards.

counting and transfer. When creating a KOP segment it is important to consider the following

rules:

● Each LAD segment must end with a coil or a box instruction. Segments cannot be concluded

with a comparison or edge detection instruction (positive or negative).

● It is not allowed to create branches that can cause a reversal of the current flow.

● It is not permitted to create branches that can cause a short circuit.

1.3 COMMUNICATION WITH A PROGRAMMING DEVICE

A CPU can communicate with a networked STEP 7 Basic programming device.

To configure communication between a CPU and a programming device it is necessary to

take into account the following:

• Configuration / setting: it is necessary to perform the hardware configuration.

• For direct communication between two devices, it is not necessary to use an Ethernet

switch, which is essential if more than two devices are connected to the network.

The PROFINET interfaces implement the physical connections between a programming

device and a CPU. Since the CPU has Autocrossover functionality, a standard or crossover

Ethernet cable can be used for the interface.

Direct connection of a programming device to a CPU does not require an Ethernet switch.

To make a hardware connection between a programming device and a CPU, proceed as

follows:

1. Install the CPU.

3. Connect the Ethernet cable to the programming device.

2. MCR-T-UI-E(/NC)

Is a Programmable Temperature Transducers for Resistance Thermometers and

Thermocouples.

A universal temperature measuring transducer for resistance thermometers and

thermocouples, with freely selectable temperature range, is available for the MCR-T-UI

converters:

– Resistance thermometer: -200...+850°C

– Thermocouples: -200...+2300°C

At the output side, the following analog standard signals can be used with normal (e. g.

0...10 V) and inverse (e. g. 10...0 V) action:

– 0...20 mA

– 4...20 mA

– 0...10 V

– ±10 V

– 0...5 V

– 1...5 V
 – ±5 V

A PNP transistor switching output (100 mA) with two switching points and eight switching

functions provides an additional monitoring function.

In this work the input range is set between 0-10V, that correspond to 0-100°C for the

temperature.

2.1 Output

The MCR-T-UI… has two outputs:

– Analog output with either 0(4)...20 mA or 0...10 V, ±10 V, 0(1)...5 V, ±5 V with normal (e. g.

0...10 V) and inverse (e. g. 10...0 V) action.

The loads must not fall below a voltage output of 10 kΩ and must not exceed a current

output of 500 Ω.
– PNP transistor switching output (100 mA) without freewheeling diode but with suppressor

diode for transient protection. You will need the MCR/PI-CONF-WIN configuration software

to program this output.

2.2 Input

The following sensor types and input signals can be processed on the input side:

– Resistance thermometer with 2, 3 or 4

-wire technology

– Thermocouples

– Thermocouples of the same type connected in series for measuring temperature

differentials

– mV voltages of -20...+2400 mV

– Linear resistors in the range from 0...8 kΩ

– Potentiometers up to 8 kΩ.

2.3 Method of Operation

The analog input signal of the temperature sensor is digitized with a 24-bit resolution and

then supplied to a microcontroller. The microcontroller forms a digital output value in line

with the temperature from the input signal. This is supplied via optocouplers to a D/A

converter after electrical isolation. The corresponding output signals are realized using a

subsequent voltage or current level (e. g. 0...10 V, 0...20 mA). The microcontroller has an
integrated memory in which the program sequence for the measured value calculation is

stored. The user-specific parameters are stored in an EEPROM (electrically erasable

programmable read-only memory). The programmed data remains in the memory even

after the supply voltage has been disconnected.

3. THERMOCOUPLE

Thermocouples are temperature sensors that work by means of two different conductors,

joined at their ends. Inside them there is an electrical circuit formed by two metal

conductors of different material welded together at their ends.

In the presence of a temperature difference between the two junctions, a current

circulation is generated, c.d. electromotive force, if one of the two junctions is opened,

which is proportional to the temperature difference; these junctions are called hot joints

(commonly called "measuring junctions"), directly exposed to the temperature to be

measured and cold junction (or "reference junction"), corresponding to the junction

between the thermocouple conductors and the measurement circuit , while the terminals

are at room temperature; the potential difference between them is proportional to the

difference between the temperature to be detected and the room temperature.

The polarization and intensity of the electromotive force generated depends solely on the

type of the two metals that make up the thermocouple and on the temperature to which

the two joints are subjected.

the cold joint is at a known temperature (usually 0 ° C), so that the current loop

(electromotive force) depends only on the temperature of the hot joint.

4. TDK-Lambda DPP-30-24

Is exceptionally compact and offers a single 30W 24Vdc 1.25A output from a universal 85 -

264 Vac / 90 - 375 Vdc 1-phase input.

potentiometer. For higher power operation, two power supplies can be connected in

parallel.

Typical applications include industrial controls, factory automation and test &

measurement.

5. BOX

The box used was created by hand using two Wirewound Resistor ,to emulate the heating

of the box, and two fans ,one as a stirrer and one to emulate the cooling of the box. Thanks

to the relays connected to these devices, and controlled via the PLC, it is possible to

simulate the behavior of a temperature regulator inside the box.

Due to the strength of the resistances it was appropriate to insert a polyurethane panel

used as a thermal insulator for the cover.