Design News, February 2013

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Automation & Control PACs Combine the Best Features of PLCs, PCs, and DCSes PACs provide a single platform for process and motion control, and also add extensive data handling and communication capabilities. T by David bark, automationDirect designed in the late 1960's to replace physical relays and timers, and as such have a ladder logic programming foundation. The PAC was designed from the ground up for programming using any one of the five IEC 61131 languages. A PAC's capabilities, however, go far beyond easier and more powerful programming. While PLCs are typically used for machine control, the PAC can easily work with more advanced and multipart automation system architectures that include process control and extensive data handling. While similar to a PLC in appearance — in terms of functionality a PAC combines the real-time control reliability of a PLC, the standard communication protocols of a PC, and the process control capability of a DCS. Although some PLCs can duplicate some of this functionality with various add-on components, a PAC has these advanced capabilities built in. A PAC is a single platform that can be used across multiple domains to monitor and control machines and processes. It typically contains many built-in features such as USB data logging ports, a Web server for remote monitoring and control, and an LCD screen for enhanced local user interface and diagnostics. Single Platform for Multiple Applications In order to perform machine and process monitoring and The PAC is fairly new to the automation world, and while control, a PAC can receive and interpret discrete, analog, and it may seem very similar to the Programmable Logic Condigital data without the need for additional interposing comtroller (PLC), it offers a flexibility and scalability far beyond ponents. For example, a PAC can easily and simultaneously the capabilities of the common PLC. PLCs were initially accept analog data from thermocouples and RTDs, Table 1: PaC advantages serial data from RFID readers, and digital values from fieldbus and device networks. This makes a PAC valu1. Combines best features of a PLC, a PC, and a DCS able for motion and process control applications. 2. Capable of process and motion control In addition, a PAC offers an open architecture that 3. Easily handles large I/O counts enables easy interoperability with other networks and enterprise systems. Since it uses standard protocols 4. Simultaneously manages analog, digital, and serial data and network technologies such as IP, Ethernet, OPC, 5. Standard network protocols streamline communication with higher and SQL — a PAC can communicate with both plant level computing systems floor devices and higher level computing systems such 6. Modular design makes system expansion easy and economical as enterprise databases — all without the need for 7. Tag name database shortens development time and simplifies changes more processors, middleware, and network gateways. oday's OEMs and end users are aware of the need to increase productivity while lowering operations and maintenance costs. Automation is a key component, but many factories and plants cannot afford the dedicated automation and IT staffs needed to maintain and upgrade complex control systems. Therefore, they're looking for automation solutions that provide real-time control in a variety of applications, along with advanced data handling and communication capabilities. To ease implementation of these solutions, needed features should be built-in, and controller programming should be powerful yet easy to understand. In many cases, a Programmable Automation Controller (PAC) can meet these requirements, delivering more power and built-in features than a PLC, while retaining ease-of-use. The right PAC will also incorporate many of the process control capabilities of a traditional Distributed Control System (DCS), while adding the data handling and communication capabilities of a PC (see table 1). Design News | february 2013 | www.d esign n –52–

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