INDEX

TITLE PAGE NO

INTRODUCTION -

PLC -

HOW DOES A PLC WORK -

HOW IS A PLC PROGRAMMED -

ADVANCED PLC FEATURES -

LADDER LOGIC EXAMPLE -

EXAMPLE LADDER DIAGRAM -

AUTOMATIC EMPTY

BOTTLE DETECTOR -

PROBLEM DISCRIPTION -

BOTTLE FILLING DIAGRAM -

PLC LADDER DIAGRAM -

EMPTY BOTTLE

DEDECTING DIAGRAM -

LADDER LOGIC DIAGRAM

DESCRIPTION -

PROBLEM SOLUTION -

INPUTS AND OUTPUTS -

PLC LADDER DIAGRAM -

CONCLUSION -

INTRODUCTION: PLC:

A programmable logic controller (PLC), or programmable controller is an industrial digital computer which has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, or robotic devices, or any activity that requires high reliability control and ease of programming and process fault diagnosis.

They were first developed in the automobile industry to provide flexible, ruggedized and easily programmable controllers to replace hard-wired relays, timers and sequencers. Since then they have been widely adopted as high-reliability automation controllers suitable for harsh environments. A PLC is an example of a “hard” real-time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.

How does a PLC work:

The PLC receives information from connected sensors or input devices, processes the data, and triggers outputs based on pre-programmed parameters.

Depending on the inputs and outputs, a PLC can monitor and record run-time data such as machine productivity or operating temperature, automatically start and stop processes, generate alarms if a machine malfunctions, and more. Programmable Logic Controllers are a flexible and robust control solution, adaptable to almost any application.

DIAGRAM:

There are a few key features that set PLCs apart from industrial PCs, microcontrollers, and other industrial control solutions:

• I/O

– The PLC’s CPU stores and processes program data, but input and output modules connect the PLC to the rest of the machine; these I/O modules are what provide information to the CPU and trigger specific results. I/O can be either analog or digital; input devices might include sensors, switches, and meters, while outputs might include relays, lights, valves, and drives. Users can mix and match a PLC’s I/O in order to get the right configuration for their application.

• Communications

– In addition to input and output devices, a PLC might also need to connect with other kinds of systems; for example, users might want to export application data recorded by the PLC to a supervisory control and data acquisition (SCADA) system, which monitors multiple connected devices. PLCs offer a range of ports and communication protocols to ensure that the PLC can communicate with these other systems.

• HMI

– In order to interact with the PLC in real time, users need an HMI, or Human Machine Interface. These operator interfaces can be simple displays, with a text-readout and keypad, or large touchscreen panels more similar to consumer electronics, but either way, they enable users to review and input information to the PLC in real time.

How is a PLC Programmed:

A PLC program is usually written on a computer and then is downloaded to the controller

Most PLC programming software offers programming in Ladder Logic, or “C”. Ladder Logic is the traditional programming language. It mimics circuit diagrams with “rungs” of logic read left to right. Each rung represents a specific action controlled by the PLC, starting with an input or series of inputs (contacts) that result in an output (coil). Because of its visual nature, Ladder Logic can be easier to implement than many other programming languages.

“C” programming is a more recent innovation.

Some PLC manufacturers supply control programming software.

Advanced PLC Features

In today’s world of the Industrial Internet of Things (I-IoT), and Industry 4.0 programmable controllers are called upon to communicate data via Web browser, connect to databases via SQL, and even to the cloud data via MQTT.

The All-In-One PLC

An All-in-One PLC integrates the controller with the HMI panel, creating a compact, easy-to-use automation solution. Users no longer need to establish PLC to panel communications and can program both the Ladder Logic and HMI design in a single software environment. An all-in-one approach saves time, reduces wiring, and cuts the cost of purchasing multiple devices.

Ladder Logic Example:

As you can see, ladder logic looks like simple control circuit schematics where input sources like switches, push-buttons, proximity sensors, etc are shown on the left and output sources are shown on the right. The ability to program complicated automated processes with an intuitive interface like ladder logic made the transition from relay logic to PLCs much simpler for many in the industry.

Although, the first PLCs were very limited in their memory and speed capabilities, they quickly improved over the years. The presence of PLCs helped simplify the design and implementation of industrial automation. For more on the history of PLCs, see this great little article from Automation Direct.

EXAMPLE LADDER DIAGRAM:

Automatic Bottle filling and Empty Bottle detection using Delta PLC Logic:

Continuous bottle filling using PLC Program:

Introduction:

This is one of the important application of PLC in the bottle filling industry where we want our bottles, which are moving on the conveyor belt, to be automatically detected at the appropriate position and get it filled by any desired liquid and also after getting filled the queued bottle gets chance to be filled. If this whole process is carried out manually it will really take a long time and also the quantities will be quite lesser. So PLC becomes requisite controller for these types of industry. Here also just a small demonstration of the process was performed with the help of PLC where a ladder diagram was created to control the process and the ladder diagram was run the PLC trainer kit to see its justification.

Automatic Empty Bottle detection

This is PLC Program for Automatic Empty Bottle detection. This logic usually found in packing industries.

Problem Description

After completion of filling process, the bottles are moved on the conveyor for packing process. Here our objective is to Detect and remove if any empty bottle found on the conveyor. Implement PLC program for this application using ladder language.

BOTTLE FILLING DIAGRAM:

EMPTY BOTTLE DETECTING DIAGRAM:

Problem Solution:

For this application, we will use S7-300 PLC and TIA portal software.

In this example, we used two proximity sensors for bottle detection and empty bottle detection.

One proximity sensor is calibrated such that it detects only empty bottle and other one is calibrated such that it detects all bottle.

Conveyor used for bottle transportation. Cylinder is used to throw empty bottle out of the conveyor.

List of Inputs/Outputs

Inputs List:

Cycle START = I0.0

Cycle STOP = I0.1

Empty bottle detector = I0.2

Bottle detector = I0.3

Output List:

Cycle ON = Q0.0

Conveyor ON = Q0.1

Cylinder ON = Q0.2

Ladder Logic Description:

In this application we have used Siemens S7-300 PLC and TIA Portal Software for programming.

Network 1

In network 1 we used latching circuit for cycle ON (Q0.0) output.it can be started by pressing cycle START PB (I0.0) and STOP by pressing STOP PB (I0.1).

Network 2

When cycle is ON, conveyor will be ON.

Network 3

When empty bottle is detected (I0.2), relay coil will be ON for internal shift register logic.

Network 4

Here bottle detector detects all bottles .Shift register will shift bit at every positive edge of bottle detector (I0.3).

Network 5

Cylinder is mounted after five steps. So when empty bottle is detected, bottle detector will count steps and after 5 steps it will activate the cylinder.

CONCLUSION:

Above application may be different from actual application. This example is only for explanation purpose only. We can implement this logic in other PLC also. This is simple concept of empty bottle detection using PLC, we can use this concept in other examples also.

All parameters and graphical representations considered in this example are for explanation purpose only, parameters or representation may be different in actual applications. Also all interlocks are not considered in the application.

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