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Housing technology

Modular systems replace single devices

Housing technology has a part to play in a recent development of the industrial market: away from single device solutions towards interconnected devices. Bus systems offer many possibilities to developers.

Bus systems make the connection and communication between device modules on a mounting rail easier (Photo: Phoenix)

THE DEFINITION OF BUS SYSTEMS varies from application to application and from sector to sector. In housing technology, this term is understood as passive plug-in components that connect multiple housing modules fitted with electronic components. The reliable and quick connection of modules is crucial because it enables the establishment of communication, for instance using CANopen or individual EIA-485 protocols. Power for both the modules and for switching can be optimally distributed using this technique. The bus systems can be configured as required. The standard solutions available on the market range from simple metal contacts to PCBs, on which high pin-count plug systems are soldered.

Housing lays groundwork for modular device system

In the past ten years, the industrial and semi-industrial market for control cabinet devices has changed rapidly. There is no halting the trend away from single-device solutions, comprising a PSU (power supply unit), a CPU (central processing unit), and a number of I/O units, towards a strategy of breaking up these units into separate, interconnected devices. Housing technology has a part to play in this development. With the introduction of bus system technology, it offers possibilities to developers who design devices like control systems.

Schematic diagram of a T-bus system with electronics housings using a possible device system configuration (Photo: Phoenix)

Bus systems allow individual devices installed in housing modules to be connected to each other. This makes it possible to replace single-device solutions, which until recently were used for cost reasons and because it was assumed they were easier to work with. The modular device systems now being developed allow servicing and maintenance on the control cabinet to be performed on site. This means that indefinite downtimes, which used to affect the machine or even the entire operation, are now a thing of the past because modules can be swapped within minutes by plugging them in or out.

The installation of the device systems in the control cabinet is scalable through appropriate programming and configuration of the electronics via the bus systems. It is now even possible to configure the device system to meet the requirements of specific applications during the installation on site. This means the technician installing the device system does not have to choose suitable transducer modules until he is on location – if the requirements of the machine are only registered during inspection.

Currents up to 42 A are connected in the connection space (Photo: Phoenix)

Different versions of the bus system

A range of bus systems with up to 16 pins in the mounting rail is currently available on the market. Systems primarily intended for data and signal transmission typically have series and parallel contacts. These contacts allow both series and parallel connections to be set up and can be used for different protocols. The series contacts, for instance, are used for the geographical addressing of device modules. In most cases, signal and data bus systems can also power the modules. For example, two pins for power supply can be used in some casees to supply power at up to 125 V and 8 A per pin.

Power bus connectors are also available for applications with high currents, which distribute a total current of 42 A with 60 VDC to individual modules on the mounting rail. This involves no wiring at all. Two power rails are plugged into the designated plug-in connectors, which in turn are soldered to the PCB of the electronics. The modules are then connected without the use of cables. This increases the functional range compared to the conventional approach of individual connecting modules using PCB terminals or plug-in connectors. In addition, a power bus system can, in most cases, be operated together with a data and signal bus system.

The BC series installation housing can be removed from the rail thanks to the H-bus (Photo: Phoenix)

With bus systems, electronic modules can also be removed from the rail without having to remove the adjacent modules. This saves a lot of time during assembly and disassembly, as well as when servicing the device system. Furthermore, some bus systems allow device developers to install their own active circuits on the PCB of the bus system. This is made possible by providing an assembly of required plastic and metal parts and plug-in connectors with up to 50 pins. The device manufacturer can then develop and produce the actual PCB for the bus system itself, or order it from a housing manufacturer.

Customized bus system PCB design using the example of a ME-PLC housing for complex electronics (Photo: Phoenix)

High pin counts and high frequencies are the future

Electronics housings are shaping the device market in the semi-industrial and industrial sector with their bus systems. The housings play a role in the modular and flexible configuration of device systems. The trends in bus systems facilitate high pin counts as well as high-frequency technology inside the mounting rail – especially the TS35.

Connection technology is also playing a crucial role with housing technology for the mounting rail. Each device has to communicate with external sensors or actuators, for example. There are a number of established products available on the housing market for this purpose. This includes orthogonal connectors with pins that connect to the PCB at right angles. Device solutions are thus developed without mismatches in terms of large PCB spaces and slim device designs.

In addition to this specific connection technology for housing systems, PCB terminals and plug-in (data) connectors are also often intended for electronics housings. The options available in terms of connectors are almost unlimited. However, a detailed assessment is necessary to determine whether a PCB with vertically connected pins can be used in a housing.