Automation & Control
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
Smart relays help to cut the cost of controls
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Fig. 1. Rockwell Automation has recently launched the Allen-Bradley Micro800 family of smart relays featuring plug-in modules, intuitive software and exceptional versatility.
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,
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