Double savings with the Bus Terminal
Extension and the “Economy plus” Coupler

An Alternative for Plant Networking

A fieldbus can offer considerable savings in material costs and decrease working time. The connection of a fieldbus station, however, still leaves something to be desired. In the majority of fieldbus systems, a significant time investment is required to wire up the fieldbus cable, and the connector itself is not inexpensive. But it is no longer necessary to cast envious glances at the network specialists installing an Ethernet system. Beckhoff have simplified the connection of I/Os to the controller.
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With a Terminal Bus Extension, Beckhoff is pioneering new approaches in electronic terminal technology. Of particular interest to the costconscious automation engineer is the increased maximum connectivity offered by this approach, which is now up from 64 to 255 Bus Terminals. The new Bus Terminal Extension increases the configuration possibilities of the well-known Beckhoff I/O system, which was previously restricted only to 64 Bus Terminals. The modular 2 and 4 channel signal terminals are connected internally via the serial terminal bus (K-Bus) to ensure fast and reliable data communication. The new extension terminal offers the possibility to expand the Terminal Bus system to more field devices, regardless of the bus system in use. By merely exchanging the standard end terminal for a KL9020 Extension Terminal, it is now possible to connect up to 1020 I/Os with a single Bus Coupler. This new design approach is a genuine alternative to distributed terminal strips with separate Bus Couplers, where several fieldbus stations are not always required. However, terminal strip solutions in control cabinets, because of space constraints, do not permit the maximum number of 64 terminals to every bus coupler. This can also be constructed in a distributed form at a significantly lower price with the extension system. Users can automate with particular economy using the latest generation of BKxx20 Bus Couplers supporting the new system of K-Bus extension.

A distributed installation, but still a unit
Thus the Bus Terminal Extension allows for up to 255 Bus Terminals in up to 31 blocks in the control cabinet or distributed over the plant. The 5 meter maximum distance between two Bus Terminal blocks means that the total reach allows up to 155 meters. Even in this distributed constellation, the Bus Coupler recognizes the terminals to which it is connected, and automatically performs the mappings of the inputs and outputs to the bytes of the process image - it treats all connected terminal blocks as one unit. The extension is thus transparent for the fieldbus and the higher-level system. An economical Ethernet cable provides the physical connection via the K-Bus from the ”master system“ using a fieldbus connection to the KL9050 Coupler. The Coupler Terminal detects a further remote bus terminal block and provides the logical connection to the Bus Coupler via the Ethernet cable. A 24 V DC supply for the field level can be fed in - electrically isolated - at these coupler terminals. The internal bus shares the same potential as the K-Bus of the Bus Coupler. S(F)TP cables with two RJ45 plugs are used for the transmission. The cables are available in various lengths for the user‘s convenience. However, versatility in use is aided, by the ability to adapt the cable to particular individual lengths using ordinary Ethernet tools. Data transmission through double-shielded cable is based on the interference- free RS485 industry standard.

Terminal Bus Extension replaces fieldbus interface
The K-Bus extension also brings advances in the field of plant networking for other types of application. There are particular economic benefits, e.g. in the connection of valve assemblies, sensor groups or LCD displays to the central system, replacing expensive fieldbus interfaces. Instead, the devices are going to be equipped with a K-Bus extension interface, which allows them to be economically integrated into the Beckhoff fieldbus system via an economical Ethernet cable. The integration of keyboard modules with the universal K-Bus interface is also imaginable, as applications for this include cases where fewer keys would be sufficient for operation of the controller, or where the PC keyboard needs to be extended with external control panels. Small control panels, located decentrally on the equipment, permit easy and local access to the machine controller. They are connected to the higher-level controller through the K-Bus extension, directly via the fieldbus.

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