What is a PLC?

A Programmable Logic Controller, abbreviated as “PLC” is a computer used to address the issues of a particular assembling process. These devices come in a wide range of shapes and sizes, with numerous alternatives for computerized and simple I/O, as well as protection from high temperatures, vibration, and electrical noise. The invention of the PLC allows for computers to be streamlined into the industrial automation process.

A PLC can be a solitary device figuring and executing operations, or a rack of various modules utilized to meet whatever your automation system requires. A portion of the extra parts include processors, power supplies, additional IO, interfaces, and more. Each part cooperates to have the option to run open or shut circle activities that are appraised at fast and high accuracy. Take a CNC machine for instance; a PLC would be utilized to control positioning, motion, and torque control. These devices are popular since they are inexpensive in relation to the amount of power and lifespan they possess. PLCs can run for hours on end. 

The diagram below displays the process of a Programmable Logic Controller system.

History of PLCs

Programmable Logic Controllers (PLCs) first hit the scene in the late 1960s. The essential purpose behind planning such a device was eliminating the high cost required to replace the complicated relay based control systems for major U.S. vehicle makers. There was a primary issue and that was that they were mechanical. This implies that they wear out and must be replaced from time to time. Additionally, relays take up too much room. These, alongside different contemplations, prompted the advancement of PLCs. More enhancements to PLCs happened during the ’70s. In 1973 the ability to communicate between PLCs was introduced. This made it possible to have the controlling circuit perform at a distance from the machine it was controlling. In several cases, the absence of institutionalization in PLCs caused a few different issues. This was improved in the 1980s. The size of PLCs was additionally decreased, which meant plants were utilizing space much more effectively. The ’90s expanded the assortment of manners by which a PLC could be modified such as block programs and a guidance list. They also observed PLCs being replaced by PC’s in a few cases. Be that as it may, PLCs are still being used in a wide range of businesses, and it’s going to remain that way in the foreseeable future.

How It Works “The Three Tasks”

The way a PLC works is very straightforward: The PLC receives data from associated sensors or information devices, processes the information, and triggers outputs dependent on pre-customized 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 that’s just the beginning. Programmable Logic Controllers are a versatile and powerful control arrangement, adaptable to practically any application.

A PLC essentially performs three tasks: a PLC checks the information inputs, goes through the program, and changes the outputs. Then, it circles back to the top and starts once more. This appears incredibly straightforward, however, it tends to be made very complex with various sources of I/O. The scan time is the time it takes for the PLC to experience the three fundamental tasks. This time is significant, as it influences how rapidly the inputs of info can be read. The sources of info should be on or off long enough for the PLC to read them. On the off chance that they are not on that long, issues begin to occur. Luckily, there are approaches to fix this issue. Perhaps the most ideal way is to utilize an interrupt at whatever point an input goes to high. This will guarantee that the PLC doesn’t miss the change.

Inputs and Outputs (I/Os)

As we’ve seen up until this point, inputs and outputs are very important to the activity of a PLC. Two key components to consider in picking the privilege PLC are the quantity of I/Os and their location. Since PLC controls undergo a large process, you will need to ensure it can deal with various I/Os. The quantity of both analog and discrete devices that your system has will affect this choice too. Remember that the quantity of I/Os will likewise decide the size of your PLC’s body. The location of I/Os will also have an effect on your choice. Will your framework require a local I/O, or will you need both local and remote I/Os? Subsystems are needed to answer these questions sufficiently. Keep in mind that the speeds and distance at which your PLC operates is important for this.

PLC Acronyms Worth Knowing

These acronyms will help you better understand what exactly you are looking for.

ASCIIAmerican Standard Code for Information Interchange
BCDBinary Coded Decimal
CSACanadian Standards Association
DIODistributed I/O
EIAElectronic Industries Association
EMIElectroMagnetic Interference
HMIHuman Machine Interface
IECInternational Electrotechnical Commission
IEEEInstitute of Electrical and Electronic Engineers
I/OInput(s) and/or Output(s)
ISOInternational Standards Organization
LLLadder Logic
LSBLeast Significant Bit
MMIMan Machine Interface
MODICONModular Digital Controller
MSBMost Significant Bit
PIDProportional Integral Derivative (feedback control)
RFRadio Frequency
RIORemote I/O
RTURemote Terminal Unit
SCADASupervisory Control And Data Acquisition
TCP/IPTransmission Control Protocol / Internet Protocol

What to Consider When Buying a PLC

  • Will the framework be powered
  •  by AC or DC voltage? 
  • Will the system be situated in one spot or spread out over a huge region?
  • Does the system run quick enough to meet my application’s necessities? 
  • What kind of programming is utilized to program the PLC? 
  • Whenever required by your application, can the PLC handle simple data inputs and outputs, or perhaps a mix of both? How am I going to speak with my PLC? 
  • Do I need to arrange availability and would it be able to be added to my PLC? 
  • Will the PLC have the option to deal with the quantity of information inputs and outputs that my application requires? 
  • Does the PLC have enough memory to run my user program? 
  • Inputs and Outputs (I/Os)

Looking To Buy?

Check out our collection of PLCs at the link “Showing PLC”  below. We provide you with the thousands of Program Logic Controllers by the brands Schneider Electric, SIEMENS, and Yaskawa at the best prices. Below are just a few PLC devices we have for sale on our website. Please visit and contact us if you have any questions.  Showing PLC.

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