It is easy to understand why in the past decade there has been a heightened interest in PC-based control for industrial automation. The PC offers powerful software tools, a floating point processor, plenty of RAM and a graphical terminal interface. Many engineers have looked to the PC as the best option when they are working to integrate advanced functionality like database connectivity, web-based interaction, analog control and simulation, and communication with third party devices.
The problem with PC-based control has always been the `control'. PCs running standard operating systems with off-the-shelf hardware are too fragile and temperamental to be relied upon for embedded industrial control. Although some engineers use special industrial computers with hardened hardware and special operating systems, many simply decide not to implement functions that cannot easily be accomplished with a PLC. Other times when engineers cannot fit all their system functionality into a PLC, they cobble together a system that includes a PLC for the control portion of the code and a PC for the more advanced analog calculations, data logging, and communication. This is why, on the floor of many factories today; you will see PLCs being used in conjunction with PCs for data logging, connecting to bar code scanners, inserting information into databases, and publishing data to the web. However, because engineers must incorporate hardware and software from multiple vendors that was not designed to work together, these systems are often difficult to construct, troubleshoot, and maintain.
Instead, engineers can now use products that provide a hybrid mix of the PC and the PLC. This new option for control takes the best features of the PC: the processor, RAM, and powerful software; and mixes it with the reliability and ruggedness of the PLC. One such product is National Instruments' Compact FieldPoint, which runs LabVIEW, a high-level development environment for embedded control. Compact FieldPoint is an embedded industrial control platform designed with PLC reliability. It is rated for up to 50 g of shock and 5 g of vibration for mobile and vibrating environments, features CE Heavy Industrial Electromagnetic Compatibility (EMC) rating for use in electrically noisy environments, and boasts a -25 to 60°C temperature range. It also incorporates features normally found on the PC such as a floating-point processor for custom calculations, an embedded interactive web server for easy control and monitoring, removable Compact Flash for data logging, and multiple serial ports for third party device communication.
Hybrid control with this type of product is advantageous for engineers who need to implement applications with custom calculations, data logging, external serial device communication, database connectivity, or web interaction. One industry that benefits from hybrid control is semiconductor manufacturing. Because some semiconductor chips produce errors at high and low temperatures, part of the manufacturing process monitors the performance of the chips under varying temperatures. Although it is possible to purchase an off the shelf machine to test the chips, these machines are expensive, offer limited temperature profiles, and do not offer the ability to generate reports and view the data throughout the plant. A hybrid system with Compact FieldPoint can control the temperature of the chamber using thermoelectric modules (TEMs) and a cool water supply. It can also read the digital lines from the chip that indicate the internal temperature. The temperature profile, which is stored on the Compact Flash, is easily updated either through Ethernet or by changing the flash card. To make operators comfortable with the new machine, Compact FieldPoint interfaces with an LCD display and keypad and provides the same temperature and status information as the unit it replaces. It also publishes a web page to where engineer can both monitor and control the process and connects over the Ethernet to a database program which stores the operations information and generates a report.
Engineers in a number of industries, ranging from semiconductor to oil and gas, are looking to hybrid PC/PLC products as a way to implement more functionality into their control systems. To learn more about hybrid control with Compact FieldPoint or to take control of a Compact FieldPoint unit from a web browser go to ni.com/compactfieldpoint.
For more information contact National Instruments South Africa, 011 805 8197, [email protected]
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