Allen-Bradley PLC Programming

Programmable Logic Controllers (PLCs) are specialized industrial computers used to automate manufacturing processes, machinery, and robotic systems. They are usually embedded devices that run only the program downloaded to them rather than being a general purpose computer. This allows the PLC to operate in a deterministic manner that provides the robustness, reliability, and predictability needed for industrial automation. This fundamental characteristic also allows for features such as live editing while a system is running which enables problem resolution and system modification without stopping a machine that is running production. Modern PLCs have built on this core robust architecture by adding in enhanced communication capabilities for interoperability and data collection as well as integrated machine safety to allow a greater level of flexibility in providing safety rated systems. In summary, their flexibility and scalability make them a cornerstone of modern industrial automation across industries like manufacturing, energy, and transportation.

Studio 5000 is the software used to program Allen-Bradley PLCs and it is also the program used in commissioning, debug, and diagnostics. Program execution can be monitored against the actively running PLC and internal variables and I/O points can be viewed both in the PLC program code itself and in dedicated watch tables. The graphical nature of ladder programming provides a visual and invaluable ability to understand how a program is operating at a glance and is uniquely suited to diagnosing issues with systems like malfunctioning I/O.

The fundamental design of a PLC that allows it to be highly capable as a platform for machine control platform also gives it the capability to optimize operations. The built-in online diagnostics provide an efficient method for diagnosing and rectifying machine problems. Modern SCADA systems and Industrial IoT (IIoT) edge platforms enables collection and analysis of production data and generation of metrics like Operational Equipment Efficiency (OEE), timing analyses, and fault logging to understand the state of your system and the potential target areas for improvement.

A well designed system is key to getting the most out of your PLC system. Start by developing system requirements, determining the number and types of I/O, and the communication to external devices. This will help chose the right PLC with the correct amount of processing speed and memory for program storage for the application. The system should then be programmed with a well-architected program following standards, such as PackML, that are appropriate for the application. The PLC, I/O, and related devices should be installed in an electrical panel designed and built to quality standards like UL 508A even if certification is not required. Electronic and physical copies of electrical drawings should accompany the system to allow for field commissioning and future diagnostics. The system should undergo a factory acceptance test before delivery and a site acceptance test after install and commissioning to ensure that all requirements are met on the delivered system. Finally, the PLC can be used to identify the need for additional maintenance through predictive maintenance programming, maintenance counters, or fault alarms that indicate the need for service.