A relay evolution – not revolution

Author : Gabriel Mancas and Mark James, Product Managers at RS Components

06 November 2018

The electromechanical relay has been a staple element in the electronic engineer’s toolkit since it was first developed in the 19th century. But as this piece asks: as a now well-established technology used in countless applications, can the electromagnetic relay really be knocked off its perch, as critics have long predicted, by the rise of solid state technology?

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Cited around 15 years ago as a written-off technology, the electromechanical relay was thought by many as something that would be replaced in the next decade with transistorised technology. But as a distributor that has served the market for more than 80 years, with its finger on the pulse of trends and technology, we continue to see undiminished demand – in fact, in our experience, the volume of relays sold each year is increasing.

New market players driving growth

This growth is driven by a combination of the increase in automated devices, and new entrants to the market helping to keep the cost per unit low – making it still a fit-for-purpose product in many applications.

The competitive landscape has evolved with the traditional market leaders seeing their dominance eroded by new, lower-cost players from the Near and Far East. Initial concerns about these new market entrants have quickly been dismissed as they have continued to increase the quality and reliability of their product. In what is essentially a commodity market, where real product differentiation is hard to achieve, success for new entrants has led to enhanced competition.

Applications driving demand

The list of areas that have contributed to the growth in electromechanical relay sales is long – from home automation and the automotive sector, to industrial automation and consumer goods. However, as digital technology advances, with applications designed to be intuitive, smart and self-learning, increasing automated control is needed to bring the output of these applications into the real world. This control is obtained with the help of relays.

In home automation, relays have always been around our homes in an inconspicuous way, and they will continue to be long into the future. Automated garage doors are controlled by relays that switch the motor used to open and close the door. Microwave timers and heating thermostats are controlled by relays, just as washing machines, clothes dryers, fridges and dishwashers all need relays, too.

More and more connected devices (such as digital thermostats) are taking the basic function of a relay as an on/off switch and combining it with IoT technology to create systems like HIVE and NEST, both of which are driving the demand for upgraded control in homes and offices – but again, still with electromechanical relays as the final link.

In automotive industries, everything in today’s modern car, from memory seats to indicators and starter motors, rely on relays. This will continue long into the future, and demand will increase even more as electric cars gain more popularity.

The industrial environment features control panels located everywhere, with each one of those panels having a number of relays within it. As industrial automation takes hold, there is a heavy reliance upon relays to control movement of machines, conveyors, and in the last few years, robots. As robots become more and more popular in the workplace, demand will increase further. And with the demand on robots increasing, so too will the demand for relays.

Specifying the perfect relay

Electromechanical or solid state?

While manufacturers will all offer their technical opinions on this, in our view, it comes down to the application and end customer. If the final product is designed to be ‘fit and forget’, due to access or the environment the product works within, and the number of switching cycles could be measured in multiples per day – then solid state is a sensible consideration and offers a true customer benefit.

Whether you select a solid state or electromechanical relay, opting for a common footprint industry-wide format for general industrial applications is a good choice. This limits the impact of any supply issues, offers brand choice, and helps within the MRO (maintenance, repair and operations) phase of the life of the relay – all benefits for the OEM and the end user.

Socket or no socket?

This, again, depends on the application.

The socket can be a weak point, as it’s a friction-based electrical connection. A good quality socket with clips will help, but when higher currents are involved, this can lead to problems. If the relay is less likely to be replaced, or vibration levels are higher, it can often prove more reliable to use a mini-contactor. These have screw terminals, no socket and can be DIN rail or surface-mounted. Many brands such as Lovato, Eaton, Schneider Electric and IMO produce affordable mini-contactors.

Saving space leads to cost savings

We’ve seen numerous examples of OEMs who construct small control panels and default to a standard, low-cost double-pole relay, with a 24mm-wide base to switch a 4 to 5A load. The focus is on the unit of this relay, and on the lowest cost option. Then a handful of these are mounted in an enclosure, making it 2 to 3 times as wide as it needs to be and often twice the price. Overall the cost of the finished control panel could be reduced by opting for a slightly more expensive (roughly 20%) slim-line interface relay, which is 6mm wide, then reduce the size and cost of the enclosure by half.

New technologies rely on relays

Relays are popular because of their flexibility and ease of use in countless applications. We’ve seen technology convergence with simple timers, voltage control and time switch devices, combining basic electromechanical switching with NFC control and programming – an electronic heart, but still using electromechanical outputs.

The solid state relay market is also growing exponentially, as research and development is geared towards automated, compact and low maintenance products, for which solid state technology holds many advantages (including flexibility and high performance).

Solid state relays become simpler to use with integral heatsinks and both ‘Normally On’ and ‘Normally Off’ operation, blurring the lines between electronic and electromechanical switching.

Additionally, solid state devices with enhanced diagnostics and communications allow great integration and low maintenance in industrial applications. However, it isn’t right for all applications, and the higher cost and thermal management aspects mean that for medium and high volume applications, the good old electromechanical relay is still king.

So whilst pundits may have claimed the end of the electromechanical relay some time ago, the evidence shows there’s still life in the old relay dog yet! With market dominance removed, new products flooding the market – and of course, technology evolving at break-neck speed – the relay has a strong role to play for years to come.

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