CFW’s electrical department does PLC programming as an integral part of its electrical systems design work. Programming can be done for various brands of PLC controllers, but Siemens is preferred where no brand is specified.

About PLC Programming

A PLC or programmable logic controller is a specialised computer used for real-time automation of electrical and mechanical systems such as industrial manufacturing lines. They are designed to accommodate multiple input-output arrangements. They are also more robust than ordinary desktop computers, being more resistant to variations in temperature and humidity, vibration, impact and electrical noise. This, together with the stability of the operating logic, makes PLCs the preferred choice for industrial operations where:

• reliability is critical (in which case desktop controllers are not appropriate),
• some system changes are expected (in contrast to remote terminal units),
• the application is highly customised.

In these cases they are often more cost-effective than the alternatives.

PLCs require relatively little electrical design, making it possible to concentrate on expressing the necessary sequence of operations using programming. The input and output systems are made for compatibility with industrial controls and pilot devices.

They are not appropriate for high-volume or very simple tasks where flexibility is not required. In these cases, the cost of developing dedicated hardware is usually justified because the unit production cost is low. Very complex tasks may also require customized solutions where the hardware has been developed with the task in mind; however, this is a more expensive solution than PLC programming.

Modern PLCs may support various forms of process control, integration into distributed control systems, and networking and motion control (e.g. for CNC machines). The logic systems provided may be able to handle PID loops (e.g. in manufacturing process temperature control).

In recent years, many PLCs have been designed for safety-critical applications. The instruction sets of these PLCs are usually restricted, with additional safety instructions added to interface with safety equipment that is part of the system.