UNIVERSITY OF MONTENEGRO�FACULTY OF ELECTRICITY�ELECTRONICS DEPARTMENT��CLASS: INDUSTRIAL ELECTRONICS�MENTHOR: PROF. DR RADOVAN STOJANOVIĆ
Students:
Marijana Kračunov
Gojko Ratković
Milica Baštrica
Anđela Kandić
Milan Rešetar
Mirza Dervišević
Časlav Labudović
Dejan Brajović
Marko Kovač
Kristina Tomović
PODGORICA, MAY 2019
EXERCISE 2: PROGRAMMABLE LOGIC CONTROLLERS (PLC)
This time we were given a task to learn how programmable logic controllers work and how to use their performances as a part of serious industrial features.
PLC (Programmable Logic Controller) is an industrial, digital computer whose hardware and software are specially adapted to work in industrial environments. Today they have been widely used in industrial control systems and have largely replaced mechanical equipments, drum sequencers and camtrimers. The system managed by the PLC controller consists of:
1) Input devices (sensors, keys, switches ...)
2) The input module, through which the signals from the output devices are received. This module is part of the PLC controller
3) Logical units or processors, consisting of a central processing unit and memory. Within this module, the data and program are placed and managed by the work of the entire system
4) Output module, through which the binary is output and the signals to individual output devices. This module is part of the PLC controller
5) Output devices (relays, motors, valves, ..)
PLC functions in such a way that it receives data from connected sensors or input devices, processes them and activates the output based on pre-programmed parameters. One of the five standard (IEC 61131-3) languages can be used for PLC programming:
1) Ladder Diagram (LD)
2) Function Block Diagram (FBD)
3) Structured Text (ST)
4) Instruction List (IL)
5) Sequential Function Chart (SFC)
PLC is different from the general purpose computer system because it does not have external memory (disks) and its operating system is simpler. The use of the PLC by the user does not require the possession of almost no knowledge of the architecture of microcomputer systems and programming, which is an additional convenience for receiving.
Today, various types of PLC controllers are developed that differ in appearance, size and processing power, starting from small units with small and limited number of inputs and outputs to large units that can be configured to work with hundreds of inputs and outputs
HOW PLC WORKS?
First, the input data is read at the beginning of each scan. Examples of input data are data
from the PLC’s physical inputs, and data that are entered via the PLC’s keypad.
Next, the program is executed. The user creates the PLC control program. The program is
composed of instructions that are written in the Ladder language, and is written using the
PLC’s proprietary software. All program instructions are executed in each scan cycle.
Last, the outputs are updated with the new data.
The PLC circuit we had been working with is Jazz Unitronics JZ10-11-R31 and is given in the picture below.S
This PLC is a compact PLC controller that contains a fully integrated operating panel and an on-board I/O configuration. Economically priced, this controller does everything a ‘smart relay’ can—plus benefits every application with full PLC functionality and a flexible operator interface.
This model comprises a total of 20 inputs in 3 groups.
1. I0 to I15 are digital inputs. They may be wired, in a group, as either npn or pnp.
2. I16 and I17 may be wired as either digital or analog inputs. These may be wired as either:
In addition, 1 input may be wired as a pnp input, while the other is wired as an analog input.
3. AN0 and AN1 are analog (current) inputs that may be wired using 2, 3, or 4 wires.
As a part of this task we worked out PLC light switch.
Light controllers have always been about turning on and turning off the lights. Lighting control systems evolved out of light controllers and they are widely used on both indoor and outdoor lighting of commercial, industrial, and residential spaces to maximize energy efficiency, improve occupant comfort, satisfy building codes, or comply with green building goals. Using the PLC as the lighting control eliminates the toggle switch wall clutter, by replacing it with a low voltage switching solution. The low voltage keypad is a momentary contact device with multiple buttons.
We used a regular resistor and photoresistor for measuring the amount of light. PLC gathers informations about voltage from voltage divider. When there is enough light, resistance is low and the bulb, wired to PLC’s output, is off. In case of less light, resistance is increased and bulb turns on.
For solving this problem we have used software U90 Ladder.
U90 ladder diagrame
Schematic
The light bulb that is connected with the rest of PLC light switching circuit will be turned on as long as the photoresistor receives smaller amount of light than the amount that is the limit one.
The other part of the problem was to create a temperature regulator using PLC, therefore here is the schematic.
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.
This is how one of the software setup solutions would look like.
And finally, here is the video of the demonstration of simple PLC led button.