Application Watch: Reed switch technology finds place in smart homes

China makers of reed switches latch onto new opportunities as the analog technology gets a niche in digital homes.

Widely adopted for proximity and sensing uses, reed switches are the component of choice in smart homes. These mature devices with established applications in household appliances, consumer electronics and security equipment offer a reliable and low-cost option in the digital setting, compared with emerging IC alternatives.

As such, suppliers in China have been building on the electromagnetic component's inherent advantages and aligning product efforts with trends for miniaturization and greater reliability to strengthen relevance for this market. Most can realize a minimum glass tube length of 6mm, close to the 5mm that foreign players offer.

There are also initiatives for the development of more SMD types led mainly by large and midsize companies. Makers such as Belong Inc. and Excel Cell Electronic Co. Ltd have released such models.

At present, however, axial leaded units rule local supply.

To boost product reliability, a few manufacturers are using dual plating for the reed blades. Instead of just rhodium as is commonly used, they employ ruthenium as well. The double layers on the contacts are said to improve adaptability to low and high loads.

Shenzhen Huaren has such models with 10W maximum rated power, 200VDC maximum switching voltage and 0.5A maximum switching current. The maximum initial resistance is 100mohm, the minimum breakdown voltage 300VDC and the maximum contact capacitance 0.4pF.

The majority of suppliers have been increasing their output as well, targeting home appliances and home security applications.

Encouraging China reed switch makers to bolster the line is the fast growth of the smart home market, a trend that is anticipated to persist in the next several years. Globally, the latter industry will be in the scale of $122 billion by 2022, registering a CAGR of 14 percent from 2016 to 2022.

The same development is forecast for the smart home sector in China. Between 2016 and 2021, the projected CAGR is 13 percent, according to China Baogao. As early as the next one or two years, this could result in an annual increase in demand for reed switches by more than 10 percent.

Exports are expected to keep rising by 10 percent. The key destinations include the US, Europe and East Asia.

About 200 companies make up the reed switch manufacturing sector in China and over 70 percent of them are local enterprises with small and midsize operations.

The line is still a minority, accounting for 10 to 30 percent of total shipments despite the uptick in output. Like their foreign counterparts in the region, local suppliers are also engaged in the production of other electronic components such as switches and reed sensors.

More than 80 percent of the companies are in Guangdong and Zhejiang provinces, and Shanghai. These areas will continue to attract entrants to the sector.

China's reed switches

Mainstream axial leaded and SMD reed switches come in 10x1.8mm, 14x2mm, 20x2.5mm and 20x3mm, with those specifically designed for smart home applications in the first two sizes.

The components have 100 to 300µs operating time. The key electrical properties include 10,000V maximum switching voltage, 5A maximum switching current and 50mohm contact resistance. The insulation resistance between contacts is 10ohm.

The products can operate in as low as -55 C to as high as 200 C. The life span is 1 billion cycles in 5V, 10mA conditions.

Most suppliers in China ensure releases comply with RoHS requirements.

All materials used, including ferronickel alloy, silver, rhodium, ruthenium, iridium, glass, nitrogen and magnets, are sourced locally. Companies purchase from foreign providers on request only.

Despite the increase in the cost of manufacturing inputs in 2017, most makers kept their prices unchanged for competitive advantage. In the months ahead, they predict material outlay and product quotes will be stable.

The products in this gallery have been handpicked by our market analyst for representing current trends in reed switches from mainland China and Taiwan makers.

SMD reed switch has maximum 0.5A carry current

Model BES08-H24B reed switch from Belong Inc. has maximum switching ratings of 200V and 10W, and can carry up to 0.5A. Its maximum static contact resistance is 150mohm and the highest dynamic contact resistance 200mohm. The maximum release time is 0.1ms.

The SMD unit measures 14x2.2mm. The minimum order is 200 units and the delivery lead time 30 days.

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SMD reed switch carries up to 0.5 or 1A

From Excel Cell Electronic Co. Ltd, model ELS4 SMD reed switch with 10W contact rating supports maximum switching at 100 or 200VDC and 0.5A. Its highest carry current is 0.5 or 1A, while the maximum operating time is 0.4ms.

Contact resistance is up to 100 or 120mohm and electrostatic capacitance up to 0.3pF. The minimum breakdown voltage is 200 or 250VDC.

The 14x2.2mm unit operates in -40 to 125 C. The minimum order is negotiable and delivered within 7 days.

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DIP reed switch with 500 or 600VDC breakdown voltage

Ningbo Deli Electronics Co. Ltd's reed switch, DLE-5C-2 model, has 300VAC or 350VDC maximum switching voltage, and 0.7A maximum switching current at DC and 0.5A at AC. The highest current it can carry is 2.5A.

The 21x2.75mm DIP variant has 100mohm contact resistance and 500 or 600VDC breakdown voltage.

The negotiable order quantity has a 5-day delivery lead time.

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DIP reed switch has 0.5A maximum switching

Sweeta Products Corp. offers model MKA-RI-90 reed switch with maximum switching voltage and current of 180VDC and 0.5A. This DIP 10W unit has 2,600Hz resonant frequency and operates on up to 100Hz. Its maximum contact resistance is 150mohm and the maximum contact capacitance 0.4pF. The minimum breakdown voltage is 220VDC.

The 20x2.6mm component complies with RoHS. The minimum order is negotiable. Delivery is within 7 days.

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