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Micro clients: the very thin clientsGünter Dumsky, product manager for Kontron Embedded Computers, looks at the way production machines and automation plants are no longer limited to being centrally controlled by traditional monolithic systems. Rather, decentralised systems that incorporate slim embedded computer systems are becoming increasingly popular. Operator control panels and visualisation units are still often integrated within controller modules, which means that the Human Machine Interface (HMI) must share resources with the controller. This occasionally degrades real-time performance of the controller or interferes with visualisation if the controller has been allocated all resources with absolute priority. With the HMI and controller on the same system visualisation units are also harder to install as, with traditional graphics interfaces, screens have to be positioned within of 10 metres of the controller. A simpler alternative is to enhance the controller with a web server and then use a single interface for the exchange of operational data. Visualisation is achieved by attaching thin clients (commonly used in the desktop IT world) that can be set up at any location in the network. Controllers are freed from having to share resources with visualisation units and the componentry necessary in the controller to support visualisation is no longer required. Enter the Micro Client: compared to traditional designs, Kontron's Micro Clients are a more slender and robust form of thin client. They require less initial investment and are cheaper to run than other visualisation options, which leads to a lower total cost of ownership (TCO). What then are the differences between these slimmed-down visualisation clients and classical thin clients? The Micro Client includes a processor that provides enough performance to support the I/O functionality, together with graphics support, touch-screen, a keyboard and mouse interface, and an RS232 interface for peripheral devices. The unit includes enough RAM to support the basic operating system, a network connection and a housing. Micro Clients are slimmer than Thin Clients, since the latter still use cooling fans, hard disks and have high-quality graphics support. Micro Clients do not support such high-end graphics since most machine controllers have no need for complex 3D animations. Simple visualisation of the operational data through a website is more than sufficient. Micro Clients can be used for more complex visualisation tasks in client-server Manufacturing Execution Systems (MES) which have traditionally used thin clients. Often complex graphic functionality is pointless in these applications and its inclusion can unnecessarily increase system costs. Kontron's M@C57 Micro Client with its 5.7-inch display is ideally suited to these implementations. Decisive advantages A slender design gives the Micro Client advantages over traditional thin clients and fully-fledged industrial PCs: At OEM volumes, Micro Clients cost approximately 700 Euro less, are more reliable and therefore require less maintenance and support. During operation Micro Clients exhibit further benefits as they produce less heat and offer improved values for EMC and electrical safety. In the event of a failure a Micro Client can simply be exchanged for another one. This enables a service technician to concentrate on faultfinding and repair any defective units without having to perform complex removal and installation procedures. While the client is being swapped, the remainder of the plant can continue to operate as normal. The design of the client means that it can be deployed with any type of decentralised controller, regardless of the controller's hardware platform and operating system. Therefore, the Micro Client is suitable for use by any machinery and plant constructors involved with decentralised automated systems. Browser-based visualisation is the simplest to achieve in most cases and all the controller needs to have is a simple web server. The server publishes all the required information, which is acquired by the Micro Client over TCP/IP and then conveyed to a browser-based visualisation unit. The Micro Client sends user commands to the controller in the opposite direction and it is not necessary for each decentralised controller to be linked to its own visualisation client. A home page on a Micro Client's browser can be configured so an operator can access as many controller websites as required. Using suitably programmed browser plug-ins, it is possible to implement the user control and visualisation of large machines that incorporate a variety of decentralised controllers using a single Micro Client. The same job could also be accomplished using conventional PCs or thin clients, but as described above, such devices are often more than is required. Development environmentSOPH.I.A is Kontron's development environment for web-based automation and it allows any controller module to be configured and put into service using a standard web browser. Entire handbooks and user manuals can be stored in distributed controller modules so that in the event of an error or malfunction, self-explanatory diagnostic information is easily accessible by an operator. This alone should reduce the need for onsite visits and remote services. Compared to pure web server applications, SOPH.I.A. offers a universal and sophisticated all-in-one package for developing, configuring and managing web-controlled applications, which includes decentralized controllers, modular distributed systems and complete automation plants. The Integrated Development Environment (IDE) and Application Programming Interface (API) enable a controller to be connected its web server, the source of Micro Client data, with only a few mouse clicks. Configurations for working with all the popular industrial fieldbuses can be set up from within the development environment and the application's interface has been designed to be independent and modular. Data providers get their data from application-specific connections and transfer it via an XML data server to the web server. Since the data provider's footprint and resource overhead are kept to a minimum, it can be loaded onto the smallest of embedded systems and it is not necessary for the XML and web server to be implemented in the same module. The web server application can be separated from the actual application and be integrated into a central homepage on its own hardware platform. Alternatively, the Micro Client can provide this functionality and a Flash Disk is available for this purpose. The first Micro Client has a 5.7-inch display, which means it can be accommodated in nearly all production machines and used as an alternative to other forms of visualisation. The M@C57 is available with two display variants: A QVGA STN display for very price-sensitive applications and a QVGA TFT display. Both display types are available with a resistive touch screen and by using X-board Computer-on-Modules (COMs), the processor performance can be chosen meet the application's requirements. RAM and Flash configurations each range from 32 to 128 MB and an additional CompactFlash socket will transform a Micro Client into a universally deployable terminal for use in server-based architectures. The TFT version also provides up to 19 additional touch screen keys that are freely configurable. Standard operating systems include WIN CE.NET and Embedded Linux and an XP Embedded version will follow. The baseboard provides conventional interfaces such as Ethernet, two USB ports as well as one RS232/485 port, and application specific interfaces include RS422/485 and CAN. Kontron offers the Micro Client together with all industry relevant services, and Micro Client M@C57 is already being used in sophisticated printing machines with decentralised controllers and in wind park windmill control systems.
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