PLC Programming Languages

In summary, PLC programming languages are basically of two types: Textual languages and Graphical languages. There are 5 programming languages under those categories:

1. Structured Text (ST)

2. Instruction List (IL)

3. Ladder Diagram (LD)

4. Function Block Diagram (FBD)

5. Sequential Function Chart (SFC) 

The first 2 are Textual languages and the other 3 are Graphical languages.

Now, let's discuss the above PLC programming languages in detail.

Introduction 

If you've ever wondered how complex industrial processes are automated, the answer lies in Programmable Logic Controllers (PLCs). These robust electronic devices have revolutionized industries by providing a reliable and efficient means of controlling machinery and processes. 

At the heart of PLC programming lies a range of specialized programming languages that enable engineers and technicians to communicate with these powerful controllers. 

In this article, we'll explore different types of PLC programming languages, their significance, and how to choose the right one for your automation needs.

What is a PLC?

A Programmable Logic Controller (PLC) is a digital computer used to control and automate industrial processes. PLCs are widely used in manufacturing plants, power stations, water treatment facilities, and various other applications that require precise control and monitoring. 

These devices are designed to withstand harsh environments, making them ideal for industrial automation.

Importance of PLC Programming Languages

PLC programming languages serve as the interface between human operators and the PLC hardware. 

They allow engineers to develop logic programs that dictate the behavior of the PLC. The choice of programming language directly impacts the automation system's efficiency, readability, and maintainability. 

It is crucial to select the appropriate programming language based on the specific application requirements and the skillset of the programmer.

5 Common PLC Programming Languages

1. Structured Text (ST)

Structured Text (ST) is a high-level programming language that resembles Pascal or C programming. It allows for complex calculations, data manipulation, and advanced control algorithms. 

ST is often preferred for applications requiring extensive mathematical computations or complex data structures.

2. Instruction List (IL)

Instruction List (IL) is a low-level programming language that resembles assembly language. 

It provides direct control over the PLC's internal operations and is often used in performance-critical applications or when optimizing code execution speed is crucial.

3. Ladder Logic

Ladder Logic is the most widely used programming language in the world of PLCs. It derives its name from the ladder-like diagram representation, resembling electrical relay circuits. 

Ladder Logic is intuitive and easy to understand, making it an excellent choice for beginners. It is particularly suitable for discrete control applications.

4. Function Block Diagram (FBD)

Function Block Diagram (FBD) is a graphical programming language that uses interconnected blocks to represent functions and operations. 

It is ideal for visualizing complex control systems and is often used in applications with multiple parallel processes.

5. Sequential Function Chart (SFC)

Sequential Function Chart (SFC) is a graphical programming language that enables the description of sequential processes. 

It is particularly suitable for applications with complex sequences of operations or state-based control systems.

 

Advantages and Disadvantages of Different PLC Programming Languages

Let's examine the pros and cons of the most commonly used PLC programming languages:

Structured Text (ST)

Advantages:

- Supports complex calculations and data manipulation.

- Resembles high-level programming languages.

- Ideal for applications with advanced control algorithms.

Disadvantages:

- Steeper learning curve for beginners.

- Requires a good understanding of programming concepts.

Instruction List (IL)

Advantages:

- Provides direct control over the PLC's internal operations.

- Optimizes code execution speed.

- Suitable for performance-critical applications.

Disadvantages:

- Difficult to read and understand.

- Limited readability and maintainability.

Ladder Logic

Advantages:

- Easy to understand and learn.

- Graphical representation resembles electrical circuits.

- Well-suited for discrete control applications.

Disadvantages:

- Limited capabilities for complex calculations.

- Not suitable for handling large amounts of data.

Function Block Diagram (FBD)

Advantages:

- Visual representation of interconnected blocks simplifies complex control systems.

- Easy to understand and modify.

- Suitable for applications with parallel processes.

Disadvantages:

- Limited availability of FBD programming resources.

- May not be the best choice for small-scale applications.

Sequential Function Chart (SFC)

Advantages:

- Enables graphical representation of sequential processes.

- Supports state-based control systems.

- Easy to visualize complex control sequences.

Disadvantages:

- Not suitable for all types of control applications.

- Requires careful design to avoid excessive complexity.

Choosing the Right PLC Programming Language

When selecting a PLC programming language, several factors should be considered:

Application Requirements

The nature of the automation application plays a vital role in determining the suitable programming language. 

For example, discrete control applications are well-suited for Ladder Logic, while complex calculations may require Structured Text (ST).

Programmer's Skillset

The expertise of the programmer should be taken into account. If the programmer is proficient in a particular programming language, it may be more efficient to use that language for development and troubleshooting.

Industry Standards

In some industries, specific programming languages may be favored due to standardization or compatibility reasons. It is essential to consider industry guidelines and regulations when choosing a PLC programming language.

Conclusion

PLC programming languages form the backbone of automation systems, enabling precise control over industrial processes. By understanding the characteristics and advantages of different programming languages, you can make informed decisions when developing automation solutions. 

FAQs

FAQ 1: Can I use multiple programming languages in the same PLC?

Yes, some PLCs support multiple programming languages. This can be useful when different parts of an application require specific language features or when integrating existing code written in different languages.

FAQ 2: Is there any free PLC programming software available?

Yes, some manufacturers offer free versions of their PLC programming software, allowing users to practice and develop programs without the need for expensive licenses. However, advanced features may be limited in the free versions.

FAQ 3: Can I convert programs written in one language to another?

In some cases, it is possible to convert programs between PLC programming languages using software tools or manual rewriting. However, the level of automation and ease of conversion may vary depending on the complexity and structure of the original program.

FAQ 4: Which programming language is best for beginners?

Ladder Logic is often recommended for beginners due to its graphical representation and simplicity. However, it is essential to consider the specific application requirements and industry standards when choosing a programming language.

FAQ 5: How can I keep up with the latest trends in PLC programming languages?

To stay updated with the latest trends in PLC programming languages, follow industry publications, attend conferences and webinars, and engage in online communities dedicated to automation and PLC programming. 

Regularly exploring the manufacturer's resources and software updates can also provide insights into new features and capabilities.

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4 Industrial Automation Certifications You Must Know

Today competition is in every field has increased a lot and to be different from other employees, we have to do different things. There are certification in every field and to get good recognition gaining certification is very important. Not only it increases competency but also gives professional recognition. So today in this post we have listed some industrial automation certification, which will help you in boosting your knowledge and career. Subscribe to Automation-Talk by Email.

4 Industrial Automation Certifications You Must Know

1. ControlLogix Certificate Program by Rockwell: Rockwell automation is a well know company in automation and their PLC's are used in every sector. So if you are a PLC programmer having experience in ControlLogix PLC's, then this certification is certainly for you. This is a self-preparatory program and you will have to follow the given syllabus.

You will complete a series of three required ControlLogix courses related to your maintenance or programming job responsibilities, plus one course elective.

To earn the ControlLogix certificate, the program requirements must be completed within 12 months. For more details please check here.


2. RSTrainer for RSLogix 5000 Software: This is another certification program by Rockwell which is a computer based training. To clear this certification you can get study material after registration and this course is available in both computer-based and web-based delivery formats and is part of a series of e-Learning courses designed to teach you RSLogix 5000 software.

Syllabus for this certification includes:

Introduction to RSLogix 5000 Software
• Installing RSLogix 5000 Software
• Identifying Main Window Components
• Configuring the Display
• Navigating through the Software
• Using Help Options

Creating and Configuring a New Project
• Creating and Managing Project Files
• Configuring a Controller
• Organizing Tasks, Programs, and Routines
• Configuring a Local I/O Module
• Organizing Data
• Producing and Consuming Tags
• Exporting and Importing Tags

Get more detail here

3. SITRAIN Certification Program: This is the certification program by Siemens and under this program, there are many certifications. This is a worldwide recognized program and the certification is valid for 3 years. Below chart shows the entry qualification for each certification.



The certifications are divided as per PLC make and model viz. Certification based on SIMATIC S7-300/-400 with STEP 7 V5.x and Certification based on SIMATIC S7-1500 with TIA Portal and there are some compulsory training which you must attend before attending these certifications. There are also certifications in the Process Automation field. Get more information here.


4. Professional Certificate of Competency in Programmable Logic Controllers (PLCs) & SCADA Systems: This certification is from Engineering Institute of Technology (EIT) which is endorsed by the International Society of Automation (ISA). This is a general purpose certification course for new learners and include basic concept of SCADA and PLC system, PLC programming (ladder logic), industrial communication protocols, PLC panel designing and much more.

Syllabus, fees and more information can be found here.

Apart from this certifications, there are many local institutes which gives you the PLC programming and SCADA training at low cost. In this program they teach about 2-3 different make PLC, SCADA, PLC programming, Electrical etc. If you know any other industry wide automation certification, please let us know through your comments.

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Best Free PLC Simulator

While in a learning phase of ladder logic we usually don't have PLC programming software to test our logic made in paper or even you don't have a PLC software for your testing and reference. In that case, you can use some free PLC simulator which are available online. There is some site which provides students and trainer free PLC simulating software. Subscribe to Automation-Talk by Email.


 

 

Best Free PLC Simulator

1. LogixPro 500 PLC Simulator by TheLearningPit.com

LogixPro 500 is the ideal tool for learning the fundamentals of ladder logic programming. The full version of our LogixPro 500 Simulator is available for download and free evaluation. What this means is that you can download and try out LogixPro 500 in a 15 day Trial Evaluation mode, and make up your own mind as to whether it's the most advanced PLC Simulator and best training value on the market today.


Recommended Article: Best PLC Ladder Programming Books

 

2. TRiLOGI PLC Simulator software

TRiLOGI" is the name of the ladder or ladder + BASIC programming software for the Nano-10, FMD and F-series PLCs via LAN or the Internet. It can also be used for programming the legacy M-series (T100MD+ and T100MX+) PLCs, although some of features are not available to the legacy PLCs.

It is a perfect training tool for learning PLC programming. Students or technicians can quickly create a ladder logic program on their laptop and instantly test the program using the simulator. Do try it.


 

3.FREE Online PLC Simulator

plcsimulator.net provide free online PLC simulator. This PLC simulator will help you to enhance your PLC programming skills. Just visit the site and test your Ladder logic skills.

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These were some of the best PLC simulator which are available online for FREE. If we find more such PLC simulator we will update your through our Email newsletter.

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PLC Programming for Tank Level Measurement using Ultrasonic Sensor

In our earlier post, we saw the PLC Logic for Auto Filling of Tank using digital inputs for LOW and HIGH-Level signals. 

Today in this post, we will see how we can measure the level of a tank using the Ultrasonic/Capacitive level sensor and accordingly ON/OFF the PUMP at low and high levels.

 

PLC Programming for Tank Level Measurement Using Ultrasonic Sensor

First of all, we need to choose the Ultrasonic/Capacitive level sensor according to our tank level height. The sensor will give a 4-20mA signal to PLC and accordingly, we will calculate the level in the tank.

PLC Logic Development:-

Now, we need to connect the analog input from the ultrasonic sensor to PLC, we have already told that in our earlier post. You can see it here.

After that, we have to write SCL (scaling instruction) in the PLC to convert the value received by PLC to the scale we want. 

For example, if the height of our tank is 5000cm, PLC will receive the 4-20ma signal and internally will convert it into a range of o to 0FA0 (hexa), and with the help of SCL instruction we will scale this value between 0 to 5000.

So that when the Ultrasonic sensor will give 4mA signal then the level in the tank will be zero and when a signal of 20mA will be received then the level in the tank will be 5000cm.

In SCL instruction, we have to define the scaling parameters in some D:-

D200 - 0
D201 - 0
D202 -5000 (hexa)
D203- 0FA0 (hexa)

Here the value 0 to 0FA0 received by PLC will be scaled to 0 to 5000 (our tank height).

Now in this PLC Program we have kept the low level at 2500cm and the high level at 4600cm. You can download the PLC program from below, we have built the PLC Program using the Omron CX-supervisor software. Both the .cxp and .pdf files are included.

Download PLC program for Tank Level Measurement.

Hope you like this PLC program on controlling your Tank according to the measurement using an Ultrasonic sensor. If you face any problem with this PLC Program or want any modification then write us in the comment section. 

Also, you can subscribe to receive the latest updates about PLC Programming languages, SCADA tutorials, HMI programming, MODBUS programming, VFD Installation., etc. subscribe to Automation-Talk by Email.

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How to Choose your PLC or PLC Choosing Criteria

Choosing a PLC or Controller for your Process is very important as it helps in cost optimization. If you choose a wrong PLC it may happen that you are out of I/O's while programming or maybe you have the excess of I/O's left which are of no use. So it becomes very important that you choose a right PLC for your Automation Process.There are several criteria that help in choosing a PLC. Before knowing the Criteria of choosing a PLC you should know basics of PLC. Subscribe to Automation-Talk by Email.

Below are some points which will help in choosing a PLC but keep in mind that you should know exactly the need of the Customers and should know how many Input and output he wants for present and for future.

PLC are chosen generally on the basis of some requirement of the company or individual person. We should keep in mind the following below point while choosing a PLC.

Some of the PLC choosing criteria are

1. Number of I/O's:

It is very important that you know the exact number of input and output that are going to be used in the process for best and economical use.


2. Type of I/O's:

The Automation Engineer should also know the type of I/O's whether he needs a digital input like Sensor, Push Buttons etc. or an analog input like RTD, thermocouple etc. The requirement for Output should be also known as what type of Output is required whether you required a digital Output like Relay, Contactor, Lamp etc. or you need an Analog output like Drive and Control Valves.


3. Memory size of PLC:

Choosing PLC memory size is also important as you may be out of space in PLC while writing a PLC program if you choose less memory size PLC.


4. Compact or Modular PLC:

Compact Type PLC are those which has Power supply and controller in the same housing while Modular type PLC has power supply and controller in a different housing. So it is good to choose compact or Modular type PLC according to your requirement.


5. AC or DC PLC:

AC PLC's are those which are operated on 220 V i.e. they require 220 V for running. Whereas DC PLC requires only 24V for Running. So you should know which type of PLC will be good for you according to the Power Supply available in your Control Panel.


6. Sinking and Sourcing PLC:

Making a PLC source at Input or making a PLC sink at input depends upon the requirement of the user so PLC should be chosen in that way. Some PLC may support both Sink and Source at Input and Output Both.

Recommended Article: Understanding Difference Between Source & Sink in PLC's

7. PLC Scan Time:

PLC scan time is a time needed for PLC to completely Scan one cycle of PLC. It may consist of reading PLC input status, clearing PLC memory, Executing the PLC program and updating the Output. The PLC with less Scan time are found to be more Costly.


8. Number and type of Communication ports in PLC:

The number of communication Port or type of communication port is also very important in choosing a PLC. Suppose you want to communicate your PLC in MODBUS but you don't have a MODBUS port so your PLC is of no use. Also, take an example where you want to communicate an HMI with RS232 port but you don't have one. So communication Port should also be in mind while choosing a PLC.

So these were some of the Criteria for Choosing a PLC which should be kept in mind while you buy a PLC. PLC choosing criteria of Allen Bradley, ABB, Siemens, Omron, Mitsubishi, GE Fanuc, Delta, Fuji, GE or any other PLC are same in all cases. Subscribe to Automation-Talk by Email for more Tips and Tutorials.

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Best PLC Ladder Programming Books

If you are new to PLC programming or want to enhance your programming skills, then you really have to work hard. For this, you will need a good mentor and good books for your help. 

Today here we will discuss some of the good PLC Ladder Logic learning books which will help you in your Industrial Automation carrier. Subscribe to Automation-Talk by Email.

1. Programmable Logic Controllers with ControlLogix by Jon Stenerson :

Programming Controllogix Programmable Automation Controllers strength is its breadth and depth of coverage, taking the reader from an overview of the Programmable Logic Controllers through ladder logic, structured text, sequential function chart, and function block programming. 

Students learn more and more easily because of the practical coverage, numerous examples, and extensive exercises.



According to one of its reader, this book is must read for beginner with no ladder logic experience. See more Info


2. Introduction to PLCs, Second Edition by Jay F. Hooper :

This book is oriented to the people that work on and troubleshoot PLCs on the factory floor. It is directed at the actual problems and conditions that will be encountered within a realistic setting. 

The text is designed to present a clear, concise picture of how PLCs operate to the person that wishes to learn more about them.



This book takes you from the beginning of understanding to the most complex problems helping you understand every step of the way. See more Info


3.Programmable Logic Controllers Textbook with PLC Stimulation Software by Max Rabiee:

Programmable Logic Controllers emphasize the practical use of the PLC in the process and industrial control systems. The textbook begins with the basics of what a PLC is and does, then guides students through the fundamentals of programming the device. 

Applications, testing procedures, and operational aspects of PLC equipment and systems are discussed. 

This text covers the most common programmable logic controller functions, providing practical examples based on the widely used Allen-Bradley Small Logic Controller (SLC 500) series of PLCs.

The wiring and programming of a PLC are covered thoroughly, using numerous examples. A supplemental laboratory manual provides a wealth of hands-on activities that will help students practice and hone their PLC programming skills.

It also includes a CD-ROM containing LogixPro simulation software with a textbook. LogixPro is the ideal tool to facilitate student learning of the fundamentals of RSLogix ladder logic programming. See more Info

Hope you will like these books and if you have any other good suggestions, please comment below.

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Conzerv Energy Meter EM6436 Modbus Communication and Connection Diagram

Conzerv has a range of EM series Energy meter and there are various different models available for your different need and according to the application. Conzerv Energy meter comes with and without Modbus communication feature, so be sure when selecting Energy Meter according to the application. If you want to communicate it with PLC then make sure that it is MODBUS Enabled.


The EM series Power meters offer complete load management facilities in a compact package. If you like to see more such posts, please subscribe to Automation-Talk by Email.

How to check whether Conzerv Energy meter is MODBUS enabled?

1) First of all, check that terminals 7 and 14 of meter does not have black dot mark, if there is a black dot market on it then it is not MODBUS enabled.

2) Secondly, check that on the front left bottom side RS485 is written and the color of the dot before this, if the color of the dot is white then it is MODBUS enabled and if it is black then it is not MODBUS enabled.



All Conzerv Energy and power meter come with different function keys in the front side for easy set up of the parameters and also some models have TURBO key through which you can directly go to set up mode.

Connection Diagram of Conzerv EM series Energy Meter

NOTE:- Click on the picture for a clear view.

In the above picture, you can see the connection of energy meter. Connect your meter accordingly. The meter has 3 line display and display the parameters sequentially one by one i.e their name and value one by one.

Now the main question is how to communicate Conzerv Energy Meter in MODBUS?

So here is the answer, first of all, make proper hardware connection of MODBUS accordingly that is connect positive of PLC RS485 port with terminal 7 and negative of PLC RS485 port with terminal 14 of Conzerv Energy meter.

Now you have to make PLC program accordingly, generally, in MODBUS we read the parameters like a line to line voltage, frequency, current, power factor etc. Each parameter has its unique address in the energy meter and it has to be read through the query in MODBUS.

Make sure to set the node id, baud rate, parity in yours Conzerv energy meter properly using the setup mode.
You can download the address map of Conzerv Energy meter EM series from here .

Click here to download.

Now the question is How to read data from Conzerv Energy meter in MODBUS using OMRON PLC.


You can review the Omron PLC MODBUS communication from here.

So here is the Data format to read:- 01 03 04 (address - 1) 02

Make sure to subtract 40001 from the address.

Response from energy meter:- 01 03 00 05 0486 9042 4800

Here the value of the parameter in response is 4248, remember that the response of Conzerv Energy meter is always in float, so make sure to convert it accordingly. For example in the above response, the value returned by EM is 4248 in float which is equal to 49.98 in decimal and it is the value of frequency.

So accordingly you can read others parameter too by using the above query format. Hope you like this article and if you do, do not forget to subscribe to Automation-Talk by Email.

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Auto Mains Failure PLC Program using Omron PLC

"Auto Mains Failure System" is Employed for Auto startup of the DG when the mains supply fails. This is a very common system and is the first step in DG synchronization. Here we will see that what is the basic concept in AMF? What hardware is required to set up AMF and how PLC Programming is done.

First of all let us understand what is AMF?

Generally, all the major industries/companies/institution have the DG for power backup, but when main power is cut off, someone has to go to start the DG and this takes time and also a man has to be kept for this purpose. So to eliminate this process PLC panel is installed to Auto start the DG when main power fails. Subscribe to Automation-Talk by Email for more such tutorial.

Working of Auto Mains Failure

When the main power goes, a signal is received to PLC and after 2 minutes DG starts. When the main supply fails signal is received by PLC then after a delay time (can be from 1 to 2 minute), the output for ACB/Contactor of DG is ON and DG starts automatically. Also, the ACB/Contractor of the main transformer if sent OFF command.

When main power comes then the signal is again sent to PLC and PLC off the ACB/Contactor of DG and after 2 seconds it on the ACB/Contactor of the main transformer and after 30 seconds it off the DG. DG is sent OFF command a little late so that the load born by DG for a long time can be compensated by running at no load for some time.

NOTE:- In 'No' condition, the ACB/Contactor of both DG and Main transformer should be ON.

So this is the main concept in DG AMF system.


In a simple system, there are generally 4 inputs and 4 outputs.

Inputs:-

1. DG ACB/Contactor close feedback.
2. Transformer ACB/Contactor close feedback.
3. Transformer Voltage Available.
4. DG Voltage Available.

Outputs:-

1. DG start.
2. DG Stop
3. DG ACB/Contactor close.
4. Transformer ACB/Contactor close.

For your better understanding below is the sample program. If you have any doubts then just write in comments and we will get back to you. Download the PLC Program for AMF:- Click here to Download.

Hope you like this article, if you do comment below and share it on social media. Hope to see you on next article.

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Mnemonic Names of Commonly used Instructions in PLC

Mnemonic Names of Commonly used Instructions in PLC

In our daily programming of PLC like ABB, Allen Bradley, Omron, etc. we use Mnemonic and some of the very commonly used instructions in PLC are as follows. We know we have missed many of them, so please help us to complete the list by commenting the other mnemonic in the comment section.

INSTRUCTION -------------------------------- MNEMONIC NAME

1. Examine if closed --> XIC --| |--

2. Examine If Open --> XIO --|\|--

3. Output Energized --> OTE --(OTE)- -

4. Branch Start --> BST

5. Next Branch --> NXB

6. Output Latch --> OTL --(L)--

7. Output Unlatch --> OUT --(U)--

8. One shot Rising --> OSR

9. Timer On-Delay --> Ton

10. Timer off-Delay --> Toff

11. Retentive Timer --> RTO

12. Count Up --> CTU

13. Count Down --> CTD

14. Reset --> RST --(RST)--



Hope you liked this simple tutorial on "Mnemonic Names". If you do, please show your love by sharing it with other and subscribing to our website.

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Importance of Emergency Button in Control Panel

Designing any electrical machine or its control panel involves proper planning, designing and commissioning. All these steps are very important for effective working of the machine and operation through it. Machine Planning is very important in the designing of the machine as it decides the future of production through it. In the planning process of Electrical machine control panel, it involves many important aspects to be followed. Subscribe to Automation-Talk by Email.





Emergency or Stop button plays a very important role in every control panel and every engineer should include Emergency button in there panel which should be in reach of the machine operator. While making a PLC program, emergency input should be used correctly so that it stops the whole machine at the time of need.


PLC Programming of Emergency Button

Programming an emergency button is very easy as you just need to add a normally closed contact in series with your PLC program. This you can do by adding the emergency contact on every rung of our ladder program at the start or can just actuate a memory bit with that and can use that memory bit everywhere you want to stop the program.

There is a big difference between emergency and a stop button though they look alike. So don’t do the mistake of not using an Emergency button in your panel.


Using Emergency button in Relay logic

If you are using only relay logic for your control panel, then also you can include an emergency button in the panel just add emergency button (NC contact) in series at the start of your electrical circuit.

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PID Control with Auto Tuning in Omron PLC

PID control as we all know is a fundamental thing used in process automation. For PID control we generally use PID Controller, but in Omron PLC there is one exclusive instruction for PID purpose. This instruction is very helpful in many application where we can minimize cost by using software PID inside PLC. In this post, we will see that how to use this PID Instruction in Omron PLC.

PID Control Feature In Omron PLC

Omron PLA is very popular in the Automation industry and used in a wide range of applications. Omron PLC have exclusive feature that we can create a PID inside PLC by using an PLC Instruction. The name of PLC instruction is PIDAT.

Syntax:- PIDAT S C D

Where S is the Input word, C is the control/Parameter Word and D is the first output word.


When the input condition of this instruction is on then it performs the PID control on the bit in word S according to the control word C. The different bits of Control word C defines the PID process parameters. Let us see the meaning of each bit of control word C. The word C defines the target value of the process being controlled.

C+1 defines the proportional band i.e the parameter for P action expressing the pro­portional control range/total control range. C + 2 defines Tik Integral Constant, a constant expressing the strength of the integral action. As this value increases, the integral strength decreases. C+3 stands for Tdk Derivative Constant, constant expressing the strength of the deriva­tive action. As this value increases, the derivative strength decreases. C+4 stands for the sampling period, the sampling period can be designated in units of 10 ms (0.01 to 99.99 s), but the actual PID action is determined by a combination of the sampling period and the time of PID instruction execution (with each cycle).

Below is the diagram explaining PID action.



PID action combines proportional action (P), integral action (I), and derivative action (D). It produces superior control results even for control objects with dead time. It employs proportional action to provide smooth control without hunting, integral action to automatically correct any offset, and derivative action to speed up the response to disturbances.

This instruction is very useful for PID block creation. Dont forget to subscribe to get all latest updates. Subscribe to Automation-Talk by Email.

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How To Set & Release Omron PLC Password

Every PLC has a feature to lock the program and Data Words inside the PLC, so that no one else can see and copy the program made by you. We do a hard job to make PLC Programs and thus also wants that no one else should take the credit of our hard work. In this article we will see "how to set and release the password in Omron PLC".

How to Put Password in Omron PLC

To set the password in Omron PLC like CPM2A, CP1E, CP1H etc., first make your program and after that in the left hand side project workspace is there. Right click on the PLC name and select Properties and Under protection tab you can set the PLC Password.


See below picture for a better Understanding.




You can also Release the Password.

To release the password just Select PLC tab -- Protection and then click on Release password. Once you have set the password in Omron PLC for Program and memory data then no one can Upload the PLC program without knowing the password. Also, the password will always be saved in the program and you can see it if you forgot what password you have put.





Also check out the Step by step procedure for removing PLC Password.

Don't forget to subscribe to get all PLC, HMI and SCADA updates in yours Inbox.

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PLC Programming For Counting Encoder Pulses

Encoder is mainly used for feedback purpose to know the position and distance measurement in Industrial applications. But before going in to the PLC Programming we should be familiar with Types of Encoder , Interfacing of Encoder with PLC.


PLC Programming For Counting Encoder Pulses / Feedback:-


Actually encoder is mounted on the shaft whose position we want to determine or want to monitor its value. Encoder have some PPR and they gives accordingly that number of pulses in one revolution.

Note:- The coupling of encoder with shaft should be done properly for accurate measurement otherwise the efficiency will decrease or it can even destroy.

PLC Logic Development:-

Now we will see the step by step detail for making the PLC Program. First of all we have to decide the condition that when should the counting start i.e when the pulses given by Encoder will be counted. Generally we want this at the auto-cycle start , So here we are considering at Auto Bit ok condition , however it can be done as per application requirement.

We here are considering the example of Omron PLC CP1H, in every PLC there is a Instruction for counting the high speed pules, In Omron it is PRV , so we will write PRV Instruction.

In PRV we have to define the port number where we have connected the Encoder and control Data. After that the value(encoder pulse value) will coming in one Data Register of PLC.

Now we have to decide as what to do this value. Let us take one example , suppose our encoder is of 360PPR i.e it will give 360 pulses in one revolution, Encoder is connected to motor shaft which is driving a conveyor and after every ever 300mm conveyor will stop and a cylinder will come down to cut.

So first we will calculate that in 1 revolution of encoder how much the conveyor moves.

If in 360 pulses conveyor moves 100 mm then we find that , for 1080 pulses of encoder conveyor moves 300mm.

Note:- Settings in the CX-Programmer.


So, after every 1080 pulses we will stop the motor and on the cylinder output and simultaneously reset the Encoder value, and continue this process. We will compare the Encoder Pulse value with the 1080 and at when they equal, motor stops, cylinder down and encoder value reset and motor again runs.

We have made the PLC Program accordingly. See the PLC Program below, we have included both the .cxp and .pdf files.

Download the PLC Program.

Also if you face any problem then you can leave us a comment. You can subscribe to get all related PLC Programs, SCADA Tutorials, HMI, VFD Installation related articles in yours inbox. Subscribe to Automation-Talk by Email for more such articles.

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Monitor PLC Scan Time in Delta PLC

Sometimes it necessary and need of time to monitor PLC scan time in PLC program, so for such situations there are some special register (D) in Delta PLC which help in performing such tasks. D1000 is such a special register which is used for monitoring PLC scan time. When the scan time exceeds the set time in the monitor timer, the red ERROR LED indicator remains shining and all outputs will be “Off”. Subscribe to Automation-Talk by Email.

The initial set value of the time in the monitor timer is 200ms. If the Delta program is long or the operation is too complicated, MOV instruction can be used for changing the set value as shown in above image. The maximum set value in the monitor timer is 32,767ms. Users can add WDT instruction (API 07) into PLC program.


When CPU execution progresses to WDT instruction, the internal monitor timer is cleared as 0 and the scan time will not exceed the set value in the monitor timer. There is one more special register D1039 which is for Fixed Scan Time and will be discusses later.

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Free PLC Softwares for Ladder Logic Programming

There are lots and lots of PLC (Programmable Logic Controller) available in the market and many PLC companies are emerging day by day with their own make and model PLC's and HMI. The best part is that they also provide free copies of their PLC software for your use. You can download the free PLC software from their website and can start learning their instructions, though the logic of all the ladder programming is same and you won't be having any issue in using this software's. Subscribe to Automation-Talk by Email.

Even if you are not a experienced PLC programmer and still searching for job in automation industry, then you should try these free ladder logic programming software to increase your knowledge and programming skills. Why you should stick to only 1-2 brands of PLC's when you can try many different PLC's logic.

Recommended Article: Best PLC Ladder Programming Books

Big automation companies like Siemens, Allen Bradley, Omron etc. do not provide their PLC and HMI software for free, you have to buy license of their software's. So it is better to have goods hands-on some of the freely available software's.


Free PLC Software for Ladder Logic Programming


1. Delta PLC Software: Delta PLC's are very popular due to their cheap cost and easy handling. Delta automation provides its PLC software WplSoft for free. Any one can download their software without any login.


2. TRiLOGI: This is one of the best ladder logic learning software for students and any student or university can use this software free of charge by just writing an email to software company.




3. Cscape Free PLC Software: This PLC software is from Horner Automation group which deals in all-in-one controllers, remote I/O, expansion etc.

Cscape is a free PLC software with drag and drop feature. It is very easy to use and you can download this software by just creating an account with them.



This software combines graphical ladder diagram programming based on IEC-1131 with operator interface development to completely integrate the control package which is definitely a great feature.


4. Eware32: This software is from Entertron Industries Inc. and work with Entertron's ePLCs only as other software's. This software also has free simulator option so it can even work without any PLC hardware.





5. KV-Ladder Builder : This is a PLC programming software from Keyence and is freely available at their website. You can download the software by creating account with them. This software also have a simulator mode, so you don't require actual PLC to test your ladder programs.


Recommended Article: Best Free Web Based Online SCADA Software


6. Do-more Designer Programming Software: This software is freely available and is from Automation Direct. This software work well in Windows XP, Windows 7 and Windows 8 also both 32 or 64-bit versions. When connected to internet it automatically checks for software and firmware updates.

There are lot more other free PLC software's available and you can download them from their official websites. If they are not full version at least you can get trail version for testing. I hope you enjoyed this article and it will benefit you in your programming and trying different flavors of PLC's. Please leave your feedback's and comments and also subscribe to our email subscription for free to get latest update on email.

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PLC Logic Auto-Filling Tank - Free PLC Programming

Almost in all of the industries Tanks are there for storing up the liquid,chemicals or there are overhead water tank for the water supply in plant.Generally for overhead tank a pump is there for filling of the tank or in other cases also there is a motor/pump for filling purpose of tank. So if the filling of tank is a manual process then a operator has to be employed for the ON and OFF process of the PUMP.

PLC Logic for Auto-Filling of Tank - Free PLC Programming

So, as told above if the process of filling is manual then we have to assign this task to a operator to ON the pump when the Tank empties and OFF the pump when the Tank fills. But in today's scenario all the process are automatic. So today we will discuss the automatic filling of tank and automatic ON-OFF of pump according to tank level. We will build a PLC Logic for this complete application. To write the PLC Program for this process we should understand the logic first.


The PLC Logic will be like following


To monitor the level in tank we can either use a Ultrasonic/Capacitive level sensor which will give analog input to PLC OR we can just put two sensor one at HIGH level and another at LOW level and they will give the signal to PLC for HIGH and LOW level respectively.


When the level will be LOW in tank then the PUMP will start and the filling of tank will start and when the level reaches the HIGH level the PLC will receive the HIGH level signal and the PUMP will stop, so the filling of tank will stop. When again tank empties the PUMP will start on its own and the process continues.


Generally the On and OFF of pump at two levels is a task that requires little intelligence. Suppose the height of tank is 5000cm then the low level should be around 2000cm and high level at 4600 cm. It is done because if for example the low level is set at 300cm hen the PUMP will start at 300 cm and suppose if at the same time the consumption rate increases than the supply of PUMP then the tank will empty. So keep in mind this thing while setting the LOW and HIGH level in Tank.

Well there is no need to install a separate PLC for this small application, as almost all the major industries have the PLC installed so the logic can be built in that existing PLC and thus there will be savings.


PLC Logic Development


Here we will take example of Omron PLC and build the PLC logic using CX-Programmer.


INPUTS :-
0.0-------------------------------------------------------------- Low level Signal
0.1-------------------------------------------------------------- High Level Signal

OUTPUTS:-
100.0 ------------------------------------------------------------ PUMP ON

Here we have build the PLC Programming using the digital Inputs, but the same can using the Ultrasonic/Capacitive Level sensor and taking the Analog input to PLC. You can download the PLC program from Below.

Download PLC Programming logic of Auto Filling Tank.

We have attached both .pdf and .cxp files so that who don't have CX-Programmer software can still view the logic and understand the PLC Logic.

We will also build the PLC logic using the Analog input to PLC, so keep visiting and you can subscribe to Automation Talk for such more PLC Programming examples, SCADA tutorials, VFD applications and HMI Programming.

If you have any doubts regarding this PLC Program then you can write in the comment section below and we will get back to you ASAP. Don't forget to Subscribe to Automation-Talk by Email.

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Using PLC Clock Time in Omron PLC Programming

Almost every plc have the clock function that is we can get the time value in the plc data words. We can synchronize the plc time with the system time at the time of program downloading. PLC stores the value of time , day , Month and year in its internal data words. We already have discussed about the plc internal words.

Reading the Year/Month/Day/Time Value in PLC :-

Many a times while developing the plc logic sometimes it is required to use the time in program to perform a particular function. Also there must be situation when we need to operate a particular device on a Specific date and time. So all these things are possible in PLC , all we need is to find out the plc system words where these values are stored.

Here we will see the example of Omron PLC. One thing we should keep in mind is that the plc must have battery installed so that real time monitoring of Date and Time is possible. In omron PLC there are 4 system words for storing the value of Year,Month,Date,hour,minute and second.


A351 to A354 are the system words in Omron PLC which stores these values. See below for the complete detail.

A351.00 to A351.07 Seconds: 00 to 59
A351.08 to A351.15 Minutes: 00 to 59
A352.00 to A352.07 Hour: 00 to 23
A352.08 to A352.15 Day of the month
A353.00 to A353.07 Month: 01 to 12
A353.08 to A353.15 Year: 00 to 99
A354.00 to A354.07 Day of the week

00: Sunday, 01: Monday, 02: Tuesday, 03: Wednesday 04: Thursday, 05: Friday, 06: Saturday

So by seeing the above values in these system words we can get the exact Date and Time. We can compare the values in these words with our pre-defined DM words and make the plc logic accordingly. Also when we download the program in plc then for the first time we have to synchronize the plc clock with our system clock. See below picture.





Now for example take a situation that we need to operate a particular output to be on 8 pm 20 Dec 2012 and be on afterward. So for this we will use compare instruction and compare the A351 with #0 and A352 with #2020 and A353 with #1212 and when these conditions gets satisfies the output will be on. If you see properly then these condition will be satisfied exactly on 8 pm 20 Dec 2012.


We hope that this plc tutorial will help you to use the plc clock time in developing plc logic . If you still face any problem you can write us in comment section. Also you can subscribe to get all latest updates in plc programming.Subscribe to Automation-Talk by Email.

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Keyence KV Studio Software

Keyence is a global name in factory automation, providing advanced sensing & measuring solutions. Including sensors, machine vision systems, bar code readers, measuring instruments & PLCs. It's a Japan based company having global reach. Keyence provide good range of automation controllers, which can be easily programmed using their PLC software called KV Studio. Subscribe to Automation-Talk by Email.

KV Studio is a PLC software which can be easily programmed and you can download its DEMO version if you want to try it. The latest version of this software is 7. "KV STUDIO" is software for creating ladder programs that combines ease of use and powerful programming processing capabilities.

Features Keyence KV Studio

1. New Unit Editor:

This function is provided for building a system for the KV-5500/5000/3000/1000/700 Series and KV Nano Series. It is used to configure the settings of and assign relays and DM entries on the units of the KV-5500/5000/3000/1000/700
Series and KV Nano Series. You can print unit structure diagrams and lists of settings.


2. Simulator function:


Simulation function is very important for offline testing of PLC program and KV Studio PLC Software also supports it. You can simulate the operation of the ladder program you have created without connecting any KV Series units. This enables you to debug the program you have created and you can also easily perform troubleshooting by conducting continuous scan execution, single scan execution, and single step execution. Reversed step execution is also possible.


2. Monitor function:


You can use the ladder program that you have created to perform online monitoring of the ON/OFF status of contacts in real time. You can display time charts. You can perform online editing.


3. Directly programmable algorithms.


Programming time is significantly reduced by the direct programming algorithm.

KV STUDIO Ver. 7 supports the KV series CPU units. Because KV STUDIO Ver. 7 has a function that automatically converts previously created ladder programs when they are read, you can smoothly migrate to the new programming environment.

This software supports PLC's like KV-5500, KV-5000, KV-3000, KV-1000, KV-700/700+M, KV Nano Series*, KV-P16, KV-10/16/24/40.

You can install this software on Windows XP, Windows 2000, Windows Vista, or Windows 7 and equipped with an RS-232C or USB interface.


KV STUDIO Ver. 7 can read the ladder programs for the KZ-300/350 and KZ-A500. When KV STUDIO Ver. 7 reads a ladder program file for the KZ-300/350 (*.ldc) or KZ-A500 (*.ldx), the file is converted into the KV STUDIO file format (*.kpr).

Downloading Keyence KV Studio Software

You can easily download trial version of this software from their official website. You will just have to sign-up and then you can download this software.


Download Keyence KV Studio Software
Note: Do download its user manual before using this software and you can easily learn how to use this software.

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PLC Programming for Dancing Light - PLC Programming

Many users mailed us for making the PLC program for the dancing light, so here we will see the PLC Logic for making a fancy light decoration system. 

This PLC program can be used for lighting systems in-house or for any festive celebration time. We will see here in detail the logic of PLC programming and the steps involved in making the PLC Program.

PLC Programming for Dancing Light - PLC Programming

Here in this PLC Program, we are considering six numbers of LEDs, 1 start push button, 1 stop push button, and 1 selector switch. We will write the PLC program for 2 different modes i.e the LEDs will glow in two different patterns.

Recommended Article: Free PLC Software's for Ladder Logic Programming

Mode 1 Pattern of LED Glowing:- While writing this PLC logic we have made the PLC program in such a way that when we will push the Start button then LED 1 will glow after 1 second LED 2 will glow and again after 1 second LED 3 will glow and so ON and after 6th LED the cycle will start again. The number of LED's can be more as per the need and application.


See the Below table for a better understanding.


Time -----------LED1 ------------LED2---------LED3---------LED4--------LED5------------LED6
T=0sec ---------OFF--------------OFF----------OFF----------OFF----------OFF-------------OFF
T=1sec ---------ON --------------OFF----------OFF----------OFF---------OFF-------------OFF
T=2sec ---------ON --------------ON-----------OFF-----------OFF---------OFF-------------OFF
T=3sec ---------ON --------------ON-----------ON------------OFF---------OFF-------------OFF
T=4sec ---------ON --------------ON-----------ON------------ON----------OFF-------------OFF
T=5sec ---------ON --------------ON-----------ON------------ON----------ON--------------OFF
T=5sec ---------ON --------------ON-----------ON------------ON----------ON--------------ON

and then again the cycle resets after every 6 seconds.

Mode 2 Pattern of LED Glowing :-

In the second mode , which will be on when we will select it by selector switch the LED 1 and LED6 will glow first for 1 second then LED 2 and LED 5 will glow and then LED 3 and LED 4 .

See below table for a clear understanding.

Time -----------LED1 ------------LED2---------LED3---------LED4--------LED5------------LED6
T=0sec ---------OFF--------------OFF----------OFF----------OFF----------OFF-------------OFF
T=1sec ---------ON --------------OFF----------OFF----------OFF----------OFF--------------ON
T=2sec ---------ON --------------ON-----------OFF----------OFF----------ON---------------ON
T=3sec ---------ON --------------ON-----------ON------------ON----------ON---------------ON

And then after 3 seconds the cycle resets.

PLC Logic Development for Dancing Light

INPUTS

0.0 --- Start Push Button -- (NO)
0.1 --- Stop Push Button --- (NC)
0.2 --- Selector Switch --- (1 pole)

OUTPUTS

100.0 ------------- LED 1
100.1 ------------- LED 2
100.2 ------------- LED 3
100.3 ------------- LED 4
100.4 ------------- LED 5
100.5 ------------- LED 6

We have considered only 6 LED here only, however, the PLC Programming can be extended for any number of LED you want, and also the glowing pattern can be changed as you like. 

If you have some any other pattern in mind and want to make PLC Logic according to that then tell us, and we will make it for you.

You can download the PLC Program below. We have attached both .pdf and cx-programmer files.

Download PLC Program for Dancing Light.

If you have any queries in PLC Programming, then write in the comment section, or want any PLC program related to Dancing Light then tell us we will make it for you.

Also, you can subscribe to Automation Talk to receive the latest updates for PLC Programming, SCADA Tutorials, HMI Programming, MODBUS and AC Motors. 

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How to Connect Omron Rotary Encoder to PLC

Encoders finds their application in various applications in industry. From Instrumentation point of view we can see Encoder as a device which provide us the pulses for rotatory movement.In Most of the applications it is used to provide the feedback and thus a better controlling.



Omron Rotary encoder E6B2 comes with open collector output and as well as line driver output. It has external shaft dia up to 40mm and it has a resolution of up to 2000PPR.


Some may want to know what is PPR in encoders ?? well PPR stands for Pulse Per Revolution i.e the number of pulses it will be giving in one full revolution.Also as per our need we can select either PNP or NPN type output. Generally in all the cases we need to interface the encoder with PLC to receive the PULSES.


The use of encoders in Automation is for detecting/calculating the length or distance traveled with the input from encoder pulses , for measuring the speed or for high-processing of data. For more detail on encoders you can see here.



How to Connect Encoder to PLC?


For connecting the Encoder to our PLC we have to make sure that our PLC accepts high speed counter inputs and we have to connect the encoder accordingly to that terminals only. Omron PLC CP1E/CP1H have 4 high speed counter inputs and we can connect up to 4/6 encoders.
Omron encoder E6B2 series have 5 wires and of different colour. Make connections as depicted below.


Wire Colour -------------------------------------------------------------Type

Brown------------------------------------------------------------------- + 24 V DC
Blue ------------------------------------------------------------------- 0 V Dc
Black ------------------------------------------------------------------ Output Phase A
White ------------------------------------------------------------------ Ouput Phase B
Orange ----------------------------------------------------------------- Phase Z

 
So connect your Encoder accordingly as shown above. Here we will tell you how to interface it with PLC. We will take example of OMRON PLC CP1E. We have to just connect 3 wires to PLC high speed counter Terminals and configure them in the software for Receiving the Pulses.
Interfacing the Encoder with Omron PLC CP1E:-

 

We will take example here as connecting the encoder to High speed counter 0.

 

Encoder Side--------------------------------------------------------PLC Side

Black-------------------------------------------------------------- 0.0
White-------------------------------------------------------------- 0.1
Orange------------------------------------------------------------- 0.4

Similarly we can connect it to any high speed counter input , just we have to check what are the terminals assigned for that HIGH Speed Counter in PLC.

After making the connections we have to write the suitable PLC Program for the reading of Pulses and processing the PV value of Encoder.

PLC Programming and necessary settings in CX-Programmer will be discussed in next post. So just reading here and also you can subscribe to get all related updates in yours Inbox. If you are facing any problem in connecting up your encoder then feel free to write in comment sections. PLC Programming for Encoder will be discussed in next post. If you like our articles do Subscribe to Automation-Talk by Email for more such awesome articles.

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