Electromechanical switches still a safe choice
28 July 2017
Despite the proliferation of touchscreen and other electronic interfaces – and repeated predictions of the demise of electromechanical snap-action switches, their sales remain healthy.
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Consumers and designers of electronic devices and systems alike want access to the latest and greatest technologies. And none more so than in the area of HMIs (human machine interfaces): it seems that every conceivable system is now controlled by a touchscreen or tablet device. They dominate home automation, portable electronic products, industrial control and automotive devices.
These new technologies, however, are not yet a universal solution for industrial, machine control, security and safety applications. Despite years of predictions that electromechanical snap-action microswitches would be replaced by cutting-edge alternative technologies, sales of these long-established electromechanical products continue to boom. Why does this remain the case in the current age of connected electronic control?
The answer is that some applications – including industrial machines, appliances, white goods, power tools and security systems – have specific requirements which cannot be easily met by electronic switching systems.
The primary requirement for any product or system design engineer is safety. Microswitches can be specified and certified with EN60335-1, a standard for the safety of electrical appliances for household use and similar purposes. Battery-operated appliances and other DC-powered devices are also within the scope of this standard.
Equipment not intended for normal household use, but which nevertheless may be a source of danger to the public (for instance, where it is used in retail or office environments), also falls within the scope of this standard. Examples of such products include catering equipment and commercial-use cleaning appliances.
Electromechanical switches also offer ease of mounting and use. For example, microswitches can be mounted to equipment or panels in any plane, with a wide range of actuator options, simplifying system design. Visible actuation makes it easy for installers and service technicians to see at a glance when a microswitch does or does not operate, aiding fault-finding.
With their wide operating temperature range – typically up to 150°C (and in some cases 200°C, to withstand internal temperatures of appliances) – electromechanical switches can be installed and operated in harsh environments. They also provide reliability and low cost of ownership – with lifetimes of up to 100,000 operations possible, and simple, low cost replacements easily switched in where required.
Finally, microswitches offer high current switching, with contacts rated up to 30A. And while electronic switching methods always have a small leakage current, microswitches have greater isolation, with a physical disconnection and typical insulation resistance of 100MO. Many of these benefits make electromechanical microswitches more suitable for industrial systems.
“ZF experienced a record year for switch sales in Europe in 2016”, Mark Mills, Distribution Manager at ZF Switches and Sensors, comments. “We have seen continued increase in demand from key customers, specifically those in the small appliance market, while competitor activity has reduced as many move their focus away from switches.”
Snap action microswitches will continue to be a viable design option for many years to come.
Their low cost, wide availability, service life and flexibility make them an indispensable component for control and safety switching requirements in consumer and industrial equipment.
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