Detect switches deliver small size, long life for smart applications


Electronic Products launches its back-to-basics electronic component series, in partnership with EDN, with an introduction to electromechanical switches. Don’t miss our discussion with Roger Bohannan, global segment leader for C&K’s medical segment product portfolio.

Since 2014, the Internet of Things (IoT) technology implementation has enabled smart connected devices to gain traction in a wide range of markets. Many smart home technologies are transitioning from passive, unconnected devices to active, connected devices. Whether at home or on the road, smart home devices enable advanced control of connected devices to simplify our lives and offer more functionality. Many of these devices are typically supported by innovative electromechanical controls or switches. As the footprint inside the IoT devices gets smaller, so too must the enabling components.

According to Markets and Markets, the IoT segment is projected to reach $1,463.2 billion by 2027, up from $250.7 billion in 2019, growing at a compound annual growth rate (CAGR) of 24.9% during the forecast period. More specifically, the global smart home market size is expected to grow from $78.3 billion in 2020 to $135.3 billion by 2025, at a CAGR of 11.6% during the forecast period. The growth is driven by various factors, such as the rising number of Internet users, the implementation of home monitoring in remote locations, increasing demand for energy savings, the expansion of smart home gadgets, and the growing concern about safety, security, and convenience among the general population.

Market trends and challenges

The potential for IoT applications is endless. IoT allows remote monitoring as well as the collection of analytic data. This data can be interpreted and used to get a 360-degree view of assets, which allows OEMs to develop products that better meet people’s needs. The general demand for IoT devices has dropped during the Covid-19 pandemic; however, new IoT devices will emerge, many related to improving health and quality of life.

Roger Bohannan, global segment leader for C&K’s medical segment product portfolio discusses key trends in the portable and connected medical device market and how they impact electromechanical switch design – Gina Roos, editor-in-chief, Electronic Products


 

The trend for miniaturization of IoT devices is nothing new. PCB space limitations require small detect switches to replace commonly used snap switches. Snap switches are traditionally much bigger and not suitable to fit into devices that are palm-sized. As a result, some 80% of the smart home IoT applications mentioned above utilize detect switches as an essential core component.

In addition, IoT device manufacturers are looking to include as much functionality and data collection as possible in shrinking product footprints. This often leads to the need for more electronics in a small package, requiring further miniaturization and design flexibility.

What is a detect switch?

A detect switch, also known as ‘detector’ switch, is a micro-miniature electromechanical switch that detects (or senses) any movement or activation on its actuator made by an object. Underneath a detect switch, there is contact termination whereby if there is an electrical signal connected to the terminals of the detect switch, the electrical signal, which tends to be in milliamps to microamps, will flow through it when the switch has been turned on. This flow through signal can be connected to other IoT devices to trigger an additional sequence of instructions that perform specific tasks on the devices.

Figure 1 A structure view of detect switch shows its main parts. Source: C&K

A detect switch provides a flexible solution for engineers to design an application whereby ‘minute’ detection is required through a moving-contact device. These switches also are very robust, whereby they can operate in thousands of lifecycles repeatedly without damage. They offer a range of travel distance detection in a small package size and meet small footprint design requirements on the PCB.

Figure 2 A micro-miniature surface-mount detect switch is seen mounted on a PCB. Source: C&K

The concept of a detect switch was derived from the traditional snap switch, as a smaller alternative to the larger snap-action switch that distributes higher current in milliamps to amps range. A key limitation of the snap switch is its size, particularly for IoT devices and other handheld devices, as these devices get smaller and lighter. Miniature detect switches offer space savings of up to 50% versus comparable snap-action switches, making them ideal for IoT applications.

Figure 3 The schematic shows the key building blocks of the HDT0001 detect switch. Source: C&K

Detect switches also use signal level current (DC voltage) for IoT devices and household electronic devices. Low-current detect switches consume little to no electrical energy, making them an ideal solution for battery type applications. No UL/ENEC certification is needed for detect switches.

Combining its miniature footprint with installation flexibility enables designers to place detect switches in almost any position, including flat, vertical and upside down. As a result, plug-and-play detect switches do not constrain designers when it comes to designing products and solutions.

In addition to the compact size, a detect switch offers many advantages. It allows the production line to use robotic machines for fast pick and place and soldering of the switch on the PCB. Over 90% of the detect switches utilize SMD termination, which means they are inherently designed for pick-and-place equipment. Without any human intervention in the manufacturing process, this can ensure the switch retains its quality, eliminating the presence of pollution and dirt generated from handling of the switch through human fingers.

How to specify a detect switch

Selecting the correct detect switch depends on the application requirements. A wide range of detect switches are available to meet almost any application demand. Options to consider include:

Size: Detect switches range from standard (~13 mm) to low profile and compact micro (~6 mm) to ultra-miniature (~2 mm) designs.

Operating life: 100,000 to 1 million cycles

Environmental conditions: They range from standard to sealed IPxx rated versions for harsh environments.

Operating force: 35 grams to 50 grams

Actuation type: Push fin, push horizontal, push vertical, and push lever-angular

Actuator length: 1.4 mm to 2.67 mm

Actuation direction: It includes vertical or horizontal, top or side, and right-angle or left.

Range of travel: 1.05 mm to 3.14 mm

Termination style: It includes SMT, through-hole, panel and snap-in/chassis and screw-mount versions for different mounting and fixing requirements.

Operating temperature range: The range -40°C to 85°C permits operation in some harsh environments.

Typically, detect switches are single pole and often only normally open or normally closed. Furthermore, when detect switches are not process sealed, there is a risk of flux penetration during soldering. This usually has to be considered during the manufacturing process of soldering the detector to the PCB.

Key applications

Detect switches are commonly used in the following smart home applications:

  • Cleaning robots: Used in the detection of dust box presence as well as the position of the robot wheel direction.
  • Smart door and window locks: Detection of the lock in forced-on position from the inside. The door cannot be unlocked manually from the outside.
  • Earbuds: Enable charging when the earbuds are docked and detect if the charging dock is in the open or closed position.
  • Security camera: Detection of lens rotation limit position
  • Security gates: Open or closed gate
  • Smoke detectors: Detection for anti-tampering of smoke detectors and alarm panels

Detect switches can also be used in a variety of other smart applications, ranging from digital cameras to detect the opening/closing of a cover, zoom in/zoom out function, and lens attachment and de-attachment to utility meters for anti-tampering by detecting the removal of the meter’s cover.

Serving all electronic designs

In order to overcome the challenges outlined here and meet industry requirements, switch manufacturers like C&K offer a wide selection of detect switches. Small and reliable detect switches are an ideal solution for all electronic designs where the footprint size is a concern. Detect switches offer the design flexibility and functionality with a range of options that enable innovative and imaginative IoT devices.

Edward Mork is product line manager at C&K.

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