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SEP-OCT 2018

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INTECH SEPTEMBER/OCTOBER 2018 45 User-created function blocks increase productivity By Bill Lydon Tips and Strategies for Integrators | channel chat independent, worldwide association for industrial suppliers and users to create specifications that increase the value and productivity of IEC 61131-3-based control- lers. For example, the standards based on PLCopen OPC UA for controllers improve automation system device interoperability. This simplifies sensor-to-enterprise, cloud, and Internet communications with PLC- open web services function blocks based on the OPC UA standard. The PLCopen OPC UA functions are a universal, secure, and reliable network communication method in IEC 61131-3-based systems. This enables frictionless information exchange based on computer industry standards. Function blocks are also available for direct machine-to-machine communica- tions between multiple vendor control- lers to coordinate automation. These new function blocks simplify the integration of packaging and other machines into these new architectures. Examples of PLCopen function certifications include: For more information about PLCopen standards and certifications, visit www. PLCopen.org. n ABOUT THE AUTHOR Bill Lydon (blydon@isa.org) is InTech's chief editor. He has more than 25 years of industry experience in building, industrial, and process automation, including prod- uct design, application engineering, and project management. messages, served-up web pages, and OPC UA messages communicating with enterprise systems using the stan - dard IEC 61131-3 PLCopen/OPC Foun - dation functions. The communication versatility allows information to be sent to local displays for a wide range of purposes, including maintenance advisories, alarms, and machine fault information. Once the function is created and tested, it can be reused with confidence over and over in any project. Functions can easily be shared with other application engi- neers on a server, via email, or using other methods. The function can be added to a library that is available for the project and for general use by other engineering staff members in the organization. There are a number of advantages to creating function blocks for a project or general library of functions that can be reused with confidence, including: n reusing tested code, which reduces er rors and increases reliability n self-documenting – easily understood n developing password-protect functions, which protects intellectual property n capturing and systemizing knowledge (information and procedures) n lowered mean time to repair n standardized specifications Continuous improvement The libraries of functions created can always be updated with improvements to the functions. If the logic and cal - culations of the functions are the only change, existing applications can be up - dated simply by changing the function library in the application project. Increasing power and scope Industry 4.0, Industrial Internet of Things, and smart factory applications are grow - ing. Implementation is simplified with user- created function blocks and a range of other standards that conform to the IEC 61131-3 standard and others defined by PLCopen. PLCopen was founded in 1992 as an O ne of the most powerful capabil- ities of programmable logic con- trollers (PLCs) that conform to the IEC 61131-3 standard is the function- ality that allows application engineers to create function blocks that can be reused with confidence, increasing project effi- ciency and quality. In addition, the grow- ing demands for more control system functionality can be efficiently satisfied by creating functions for applications. These include: n real-time data links to information technology systems n "make to order" manufacturing de- mands n process synchronization n control to optimize processes (i.e., in- crease quality and save energy) n real-time maintenance information Function blocks have inputs, defined operation, and outputs that are linked to- gether to create applications. PLCs come with a number of functions that are stan- dard, for example, ADD, SUBTRACT, MUL- TIPLY, DIVIDE, PID, TIMER, DELAY. PLCs conforming to the IEC 61131-3 standards enable control and automation engineers to create their own function blocks for applications. This is a powerful tool for improving quality and productivity. The application engineer simply defines: n Inputs to the function, including data type for each (including field point in- puts, integer data, floating-point data, string data, time, and array data) n Logic and calculations for the func- tion. This can be done using ladder logic, structured text, or other function blocks. The functions can be simple logic or complex calculations (e.g., scaling a nonlinear sensor, staging multiple com- pressors, part load control strategies, communicating your messages, overall equipment effectiveness calculations, and performance calculations). n Output of the function, for example control outputs, constants, local vari- ables, and global variables. The out- puts can also be email messages, SMS

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