The Beginner’s Guide To PLCs: What You Need To Know

When we were children, many of us learned that there were six simple machines that made many of the large tasks we faced easier. Now that we’re adults, we know there is far more than levers, pulleys, and wedges to make our lives easier—and these machines are far from simple.

Take the machinery used to manufacture the items we use in our everyday lives, for example. We design this equipment to create complicated designs quickly and precisely. To do that, they require a component called a PLC.

To better understand how they function, we have compiled the beginner’s guide to PLCs and what you need to know about them.

What Is a Programmable Logic Controller?

PLC, or programmable logic controllers, are small, powerful computers built into servo drive systems. Manufacturers program these computers to send messages to the rest of the machine, namely messages about what function the machine should perform.

The PLC also constantly communicates with the system’s feedback encoder. The computer takes this information, processes it, and tells the machine to adjust its movements and speed accordingly. Without the PLC controller, machines would not be able to move with as much precision as they have otherwise.

Parts of a PLC

Even though the programmable logic controller forms one component within the whole servo system, it is made of multiple parts itself. Those three parts are the power source, central processor, and input and output devices.

Power Source

This is the most straightforward of the components. As the name suggests, the power source is what supplies electricity to the programmable logic controller. This power source supplies electricity in the form of alternating current (AC), which it then converts into direct current. (DC)

Central Processor Unit (CPU)

This is the central and most significant part of any PLC. It is where manufacturers can enter their preferred program into the system. PLC CPUs tend to use one of six different programming languages:

• Ladder diagrams
• Instructional lists
• Structured text
• Sequential function charts
• Function block diagrams

This is also the part of the machine responsible for responding to feedback from the encoder, processing this data, and issuing new commands.

Input and Output Device (I/O)

But in order for the CPU to receive the necessary data or send out a command that determines a machine’s next actions, another device is needed. These devices, referred to as input/output devices (I/O), are responsible for this action.

While I/O devices are often directly attached to the CPU, this is not always necessary. In some instances, the I/O is in another room or building from the rest of the unit, allowing it to take in data with greater ease. From here, it is still able to send the data to the waiting CPU.

Precursor To PLC: Relays

To better understand programmable logic controllers, it’s helpful to understand what came before them: the relay board. These cumbersome panels were made up of a series of switches that manufacturers would have to set manually.

Although effective in their own way when set, these machines were incredibly difficult to reset when manufacturers needed to change the logic. They were also complicated, inefficient, and prone to shutting down.

Benefits of PLC Over Relays

With all the pitfalls of the relay system, it’s easy to imagine how switching to a digital system can offer improvements. And these core benefits are essential things to know about PLC systems.

More Flexibility

As mentioned, relay systems were incredibly difficult to reprogram after they were already set. That’s because the system was based on a system of physical switches.

As long as you are well-acquainted with the proper programming languages, you can readjust a PLC unit with ease. This is especially true if your system uses a ladder diagram as its programming language. This system is visually based on a system of relays, making it simple to transition to the digital system.

It is also far easier to expand the system with other physical components or digital features like timers. This makes it a good choice for companies that are likely to expand in the future.

Greater Efficiency

One of the challenges with the relay system was its complexity. There were more wires, and every individual stage of production took longer, such as booting up and scanning.

The beauty of the PLC system is that it uses far less wiring and requires less physical management. Even so, it is able to perform functions much more quickly, cutting down on overall production time.

Low Maintenance

The smaller physical presence means that there are fewer mechanical parts. That means less friction, leading to parts becoming worn down more slowly.

This has a plethora of benefits for your company. First, machines tend to last longer and experience less downtime. This reduces maintenance costs as well as costs to your company’s workflow and productivity.

Less Space

Along with maintenance benefits, the smaller physical presence is also convenient for your workspace. Less space is being taken up on the production floor, giving you more space for machinery and reducing tripping hazards for those working in the area.

Additionally, as mentioned, PLCs have the possibility of being split up so that input and output devices can be placed in a different room from the central processing unit. This offers companies more options as far as setting up their own production spaces.

More Environmentally Conscious

Relay systems require a great deal of electricity. This costs you more money and increases your company’s carbon footprint. The efficiency provided by PLCs means that they use less electricity to perform the same tasks, making them a more eco-friendly option.

The wider environment isn’t the only one PLCs improve, though. Relays tend to produce more heat and noise because of their mechanical components. This can make the production floor a much less pleasant place to be, especially in the summer. PLCs produce less heat for a cooler, happier manufacturing plant.

PLCs are far from simple machines, but they do greatly improve the way we handle large tasks. That’s why we offer used PLC parts for sale to help you keep your systems online for all the momentous tasks your company needs to accomplish.