Fig. 1. Rockwell Automation has recently launched the Allen-Bradley Micro800 family of smart relays featuring plug-in modules, intuitive software and exceptional versatility.


4 Machine builders and original equipment manufacturers needing to incorporate controls in their designs had limited options until the introduction of ‘smart relays’. Jon Severn looks at recent developments in smart relays and accessories.


4 Les fabricants de machines et d’équipements originaux qui ont besoin besoin d’incorporer des contrôles dans leurs conceptions avaient des options limitées jusqu’à l’introduction de « relais intelligents ». Jon Severn observe les récents développements en matière de relais intelligents et accessoires.


4 Bis zur Einführung von „intelligenten Relais“ hatten Maschinenhersteller und OEM, die Steuerungssysteme in ihre Designs integrieren mussten, nur begrenzte Möglichkeiten. Jon Severns untersucht die neuesten Entwicklungen bei intelligenten Relais und Zubehör.


Smart relays help to cut the cost of controls


A


ll but the simplest of powered equipment needs to be controlled in some way. Even lighting, which can be controlled adequately with a simple switch, can benefit from


additional controls, as then the lighting can be made to stay on for defined periods, switch on and off at predetermined times, or switch on when one or more sensors are triggered. Traditionally such a control system would have been assembled using relays and timers, but ‘smart relays’ are a simple, low-cost alternative that offer an additional advantage in that they can be reprogrammed to modify the existing functions or to enable the smart relay to be reused on a completely different application. In fact smart relays have more in common


with programmable logic controllers (PLCs) than conventional relays, yet the term ‘smart relay’ is used to differentiate them and emphasise the lower price compared with even the smallest of conventional PLCs. They are programmed either by means of pushbuttons and a small screen on the front panel or, alternatively, via a computer. Smart relays were first introduced over a decade ago; very soon there were numerous different models


available from suppliers of automation products, and it quickly became apparent that some were rebranded versions of others. Today there remains a wide choice of smart


relays, still with many products being rebranded versions of others. A search of the internet can help to identify which of these are identical and which have minor differences. However, given the step- change in technology that smart relays represented when they were first introduced, there seems to have been relatively little development since then. Perhaps the most important movement in this


area has come from Rockwell Automation, with the launch in February 2011 of the Allen-Bradley Micro800 family of smart relays. Featuring plug- in modules, intuitive software and exceptional versatility, these devices are said to enable engineers to specify a controller that fulfils the exact needs of their application (Fig. 1). Steve Pethick, director of components and


safety business, EMEA, at Rockwell Automation, states: “Machine builders need economical, convenient control solutions they can customise to suit specific application needs. With this new line, we are delivering the functionality and flexibility of a micro PLC for the price of a smart relay. The


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