Switches
Relays for Smart Homes R
By Juergen Schoenauer, European relay technology manager at Omron Electronic Components Europe
elays are playing an increasingly important role in building automation systems. Controllers, sensors, switch
actuators, timers, lighting and other control devices, motors, pumps, alarm systems and access control systems are all used to automate building technology and make it more convenient and safer.
The challenge: controlling the system Various bus systems such as KNX and LON, which allow such devices to communicate with each other, have established themselves in the marketplace. Wireless systems can also be retrofitted in buildings. Ultimately, all of the above-mentioned components fulfil an extremely wide variety of tasks for convenience applications such as blinds control and lighting. These applications also include access control and control
tasks.Building and room temperature applications require accurate temperature sensing and control. Heating and air conditioning units and their
actuators such as pumps, motors and valves are usually activated by relays. The safety of buildings, i.e. intrusion and fire protection, is becoming more and more important. Alarm systems turn on lighting or alarm horns or sirens.
Why a relay? Open the case of almost all of the building automation applications listed and you’ll find an electromechanical PCB relay is used at the output. With so many alternative switching technologies available, including solid state switches, this may come as a surprise. There are four really great reasons behind this. • Relays have one or more relay
contact outputs, • Contacts can be supplied with a
changeover output which is used for interlock or scanning circuits; • Relays can individually switch AC or DC voltages; • Relays simultaneously meet insulation and glow wire test requirements.
Relays are still a great
solution: multifunctional components that are relatively inexpensive and easy to add to any circuit.
Connecting logic to load You can think of the relay as the device that does the heavy lifting: connecting the delicate (low voltage, milli-Amp current levels) logic circuitry to whatever load is being controlled typically at a high (mains) voltage and several Amps of current.
Challenges Because loads vary enormously and the latest technologies place new demands on relays, Omron has developed platform relay series G5Q. This family offers different specifications the same PCB connection to meet different switching needs. In common with other classes of
components, relay manufacturers are being challenged to make their components more compact to make room for additional components on the PCB. Designs that are almost 30mm long used
to be perfectly acceptable – now they are now no longer up to date. Specific applications have their own
challenges. For example, innovative LED lighting, highly efficient water pumps and capacitive input filters with Power Factor Correction produce high inrush currents. This puts extreme loads on relay
contacts. If relay contacts weld together this destroys the relay and thus the device. Type G5Q-1A-EL2 (Figure 1) was developed for capacitive inrush currents in the µs range. Such relays can switch inrush currents of 40 A/100 µs and nominal cut- off currents of 1 A/250 V AC up to 100,000 times.
RFI /EMI shielding gaskets & components
www.kemtron.co.uk +44 (0) 1376 348115 ·
info@kemtron.co.uk www.cieonline.co.uk Components in Electronics June 2019 15
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