An alternative to conventional electro mechanical switches

6th November 2015
Nat Bowers


Energy harvesting switches offer a maintenance-free, simple-to-install, long-lifetime alternative to conventional electro mechanical types.

By Thomas Boethe, Product Manager, CHERRY Electronic Systems.

In our increasingly connected world, there is growing demand for low energy consumption, simple to use and flexible data transmission. CHERRY have developed an innovative wireless and batteryless energy harvesting technology which can provide cost-effective switching solutions in a wide range of environments and applications. Energy harvesting applications can be found in almost every market sector, including industrial installations, building automation, smart home and medical. Designed for global use, the technology enables CHERRY to offer an excellent alternative to wired or battery-powered solutions. Compatible with multiple wireless protocols, the products are suitable for global use across countless markets and applications. As there is no need to change or dispose of batteries, the solution is both environmentally friendly and maintenance-free.

The CHERRY energy harvesting product portfolio includes a stand-alone generator and a number of packaged switch variants including a rocker switch for actuation by hand and a snap-action switch for mechanical actuation by a machine or proximity switch.

Wireless receivers to work with CHERRY switch modules are available as either a self-contained packaged module, or as an ‘RF stamp’ for OEM use complete with wire antenna and without an enclosure.  The receiver module has multiple output options (i.e. RS232 TTL) and is suitable for wall-mounting.

Activating any switch variant provides data transfer via RF technology, eliminating the need for expensive and complex cabling and increasing flexibility of use. Flexible pairing allows the operation of several switches with one receiver and vice-versa. Each switch has a ‘unique ID’, providing clear identification when operating several switches at once. Up to three ‘telegrams’ are sent per actuation with pseudo-random timing to ensure robust data transmission.

Energy harvesting generator technology overview

Based on the inductive principle, the direction change of the magnetic field in an inductive magnetic circuit transforms mechanical energy into the electrical energy required to send an RF signal from the patented energy harvesting generator.

Energy harvesting generator technology overview

This technology is then packaged and assembled, together with an operating mechanism, resulting in the raw form of the standard product - the generator.

CHERRY’s energy harvesting generator

CHERRY’s energy harvesting generator

The Energy Harvesting Generator is available separately for OEM applications with or without the RF electronics and integrated into CHERRY’s Energy Harvesting switch modules. It consists of a coil and a magnet block which is actuated when a mechanical force acts vertically on the end of the generator’s lever. A patented mechanism causes the magnetic block to move down abruptly (switching) and a positive pulse is created by reversing the polarity of the coil. When the lever is released, the system returns to the initial position (resetting) by means of the mechanism and a negative pulse is created. The energy produced is used to transmit a wireless signal indicating operation of the switch.

CHERRY’s energy harvesting generator with wireless transmitter electronics

CHERRY’s energy harvesting generator with wireless transmitter electronics

The initial energy pulse created provides the harvested electrical power output, which is then transformed and averaged over time by internal energy management components to create the supply voltage for the wireless transmitter. The small size, high efficiency and long life expectancy (up to 1m cycles) makes the product, in either form factor, ideal for installation in tight spaces without having to take in to consideration routine maintenance.

Overview of the generator and RF generator module

Overview of the generator and RF generator module 1

In addition to pre-assembled switch modules for general HMI purposes use two switch modules have been designed specifically for building automation, a 1-way and a 2-way pushbutton.

Overview of the generator and RF generator module 2

Key benefits of using energy harvesting powered switching systems include; wireless signal output, no power source or battery required, energy saving, low system installation and maintenance costs, flexible system design, long lifetime, simple installation, maintenance free and eco-friendly.

Typical applications include: smart home light switch or handheld controllers; RF enabled bulb control; wall socket outlet or adapter control; window handles linked to room thermostat; building and office automation; industrial control limit switches; control pedals; emergency stop actuators; and machine remote control.

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