In the world of industrial automation control solutions, there are two major control systems that are used: PC-based controls and PLC (programmable logic controller) based controls. While both controllers are commonly used for applications in a variety of industries, there are differences between the two control solutions, and it’s these differences that make PC-based control a better choice for some applications.
The Difference Between PC and PLC Control
PLC controllers and PC can be used to automate specific functions of machines, entire processes, or even entire production lines. These processes can include timing, control, sequencing, and starting and stopping motors, pumps and valves. The primary thing that sets PLC control apart from PC based control is built in or snap on I/O (input/output). Many types of I/O can be combined in a PLC, analog, digital, thermocouples, and more. While PC control systems have the same types of IO available, the IO is often distributed on a deterministic network.
PLCs often need to be connected to other systems (typically PC based) in order to complete tasks like supervisory control and data acquisition (SCADA), SQL database management, and IIoT. Often PC based controls have these software features and network capabilities built in.
PC Hardware and Software
Since IPCs (Industrial PCs) use the same hardware and software as hundreds of millions of other PCs across the world, there are no shortages of new updates, products and technology to use. IPCs are widely available, versatile and easy to implement into a system. When the hardware and software used in a system are so mainstream, it’s guaranteed that users will always have state of the art computing power at their fingertips. IPCs often mimic a standard office PC in function, making them familiar to operate and maintain.
IPCs may use Microsoft OS, Linux OS and other operating systems to control non-real-time tasks, which means the IPC can be used for multiple tasks beyond the cyclic control tasks. Additionally, IPCs can combine real-time Operating Systems with a non-real-time OS. A Real-Time Operating System (RTOS) is a computing environment that reacts to input within a deterministic time period. A real-time clock and turn around reaction time can be often measured in micro-seconds. IPCs also have easy connection to the enterprise network using Ethernet (NIC) connectivity.
The Costs and Maintenance
Because IPCs are not a niche market the costs to purchase and maintain these types of control systems are typically lower for a given processing speed or update rate. IPCs also come in a wide range of sizes and power and can be purchased with options that include fan-less or high IP ratings (IP67 or higher). Maintenance and replacement may be significantly easier and options to upgrade abound. Often an IPC from one manufacturer can replaced with an IPC from another. When processing or computing power becomes a limiting factor, there are usually options to upgrade the processor speed, memory (Volatile and Non-Volatile), port options, number of network interface cards (NICs), etc.
IPCs have the capability work with all controllers (including PLCs) and networks like EtherCAT, Ethernet/IP, Modbus TCP/IP, and more. This allows for a more streamlined, purpose-built control architecture that is flexible and scalable.