Programmable Logic Controller: What Is a PLC and How Does It Work?

Interconnectivity has become an increasingly critical component of the modern-day manufacturing facility. As manufacturers continue to invest in smart devices such as Industrial IoT, network-connected machinery, and similar digital tools, they must establish a way to communicate with their equipment and automate processes with minimal human intervention.

In a more traditional manufacturing setting, individual machines and control systems are connected to each other directly. However, this kind of setup can be more complex and more challenging to manage.

Modern manufacturers get around this hurdle by installing and utilizing programmable logic controllers (PLC). Instead of physically wiring each machine or piece of equipment directly to relevant control systems, manufacturers connect equipment to PLCs, making for a more integrated production process control.

In this post, we’ll discuss how programmable logic controllers are used in manufacturing facilities, what benefits they provide, and how Tulip can be used as a PLC to automate process control across machines and digital tools in your operations.

A programmable logic controller is a small computer programmed to carry out specific actions or outputs based on the inputs it receives along with a set of specific rules.

PLCs are used in a wide range of commercial and industrial settings including airports, office buildings, railways, and manufacturing facilities. In this post, we’ll review the implications of PLCs in the context of manufacturing specifically.

Connecting your equipment and systems using a PLC differs from the more traditional approach that entails using relay logic systems. While electrical relays work to control industrial processes similar to a PLC, they also pose significant drawbacks when it comes to both configurability and maintenance.

Because electrical banks are made up of a system of physical wiring, should the operation of the system ever need to be changed, the physical connections would need to be completely rewired.

Additionally, should a failure in the system take place, it would require the responsible personnel to patrol the entire system to identify the cause of the prevailing problem. Depending on the complexity of the system, this can take a significant amount of time and resources. Here’s an example of an electrical relay room for reference.

With the introduction of solid-state electronics and microchips, the command logic used by electrical relays is replaced with software logic, making PLCs significantly easier to configure and maintain.

Additionally, PLCs are built to withstand the harsher conditions often found in industrial settings making them great for manufacturing facilities.

To understand how a PLC functions, one needs to know its structural setup. This features a central processing unit sandwiched between an input and output module. The CPU is also connected to a programming device, most commonly a desktop computer.

Manufacturers use the computer to program the PLC’s CPU. This program provides the controllers with the logical steps for processing incoming data.

The factory equipment is connected to the input and output modules, depending on the desired process. In several common instances, manufacturers have human-machine interfaces (HMI) connected to the input module as well.

The PLC obtains inputs from equipment and HMI. Next, the controller’s CPU runs the logic program to determine the kind of signal to send to the output module to effect change in the desired equipment.

This program might control several complex systems, including valve control, safety shutdowns, temperature modulation, and other production processes that require close monitoring or automation.

With the proliferation of more machinery across a manufacturing facility, businesses have resorted to finding new ways to automate processes and streamline production. The increased automation led to the adoption of using programmable language controllers to connect and control the various machines, devices, sensors, etc. Some of the benefits that PLCs provide manufacturers include:

Easier programming: As discussed, relay systems require manufacturers to deal with complicated logic sequences, making the entire ordeal more challenging. PLCs, on the other hand, can be programmed in basic programming languages to control various industrial applications.

More flexibility: If manufacturers need to adjust their production processes, they can easily do so using a PLC. This is because the logic program can be easily edited via the connected computer, differing significantly from having to unwire and rewire an entire relay circuit. This allows for easier troubleshooting and maintenance over time.

Improved reliability: The fewer wiring requirements in PLC-centric automation present fewer chances for unreliable physical connections. As such, manufacturing processes can go on more reliably.

Fast response time: Modern manufacturers need instant responses to in-factory events. PLCs control machinery in real-time, enabling them to respond to inputs immediately.

For instance, if a machine’s temperature starts to shoot up, the PLC can shut down the machine almost instantaneously to prevent a more catastrophic event.

Physically robust: PLCs are built to be rugged, making them resistant to potentially extreme factory conditions like heat, dust, and debris.

When turning to programmable logic controllers for production automation, manufacturers need to consider some key factors before procuring a PLC.

These include:

• System compatibility: Manufacturers should know if their PLC of choice is compatible with their current manufacturing systems. In addition, the PLC should also be compatible with the factory’s power outlet voltage.

• Processing speed: The PLC’s CPU should possess enough processing speed to handle the various processes and functions in a given facility.

• The number of ports: It’s smart to ensure that the PLC has enough input and output ports to cover factory requirements.

• Analog I/O capability: Some PLCs can only handle simple on/off processes – discrete functions. However, some manufacturing operations have analog processes, requiring a programmable logic controller that can handle continuous variables.

• Durability: Many manufacturers position PLCs in the vicinity of the equipment of interest. Therefore, it’s important to ensure it can handle industrial environmental factors like high temperatures.

In recent months, Tulip launched Edge IO, a wifi-enabled, easy-to-implement, low-cost edge device for collecting operational data. Our Edge IO device integrates data from various machines, sensors, and PLCs, with industrial I/O ports as well as USB connectivity.

Using Edge IO, workers can change PLC programs from Tulip apps, and our Edge IO device can be transformed into a PLC without incremental hardware cost. You can see how Tulip is used in this context with the demonstration below.

If you’re interested in learning how Tulip can help automate your industrial automation processes, reach out to a member of our team today!