Algra developing Finger-Powered Wireless Piezo Switch

wireless piezo switchSwiss company Algra is developing a finger-powered piezo wireless push button, aiming it at stick-on light switches and other building control applications.

The technology, dubbed Dynapic, is based on low-movement piezo keyboards that the company has been making for hygiene and vandal-resistance for over 30 years.

“We have a piezo membrane similar to that in a beeper – a ceramic placed on a plate which is bent from 10 to 100µm,” CEO Dieter Matter told Electronics Weekly.

Piezo generators produce high-voltages at low current, and a wireless node is going to need, say, 3.3V at tens or hundreds of µA.

How is Algra dealing with the power conversion?

“How we do it is somewhat of a secret, and development is still going on,” Matter said. “We have samples to prove that it works.”

wireless piezo switch

The converter has been developed with the Zürich University of Applied Sciences and Swiss chip firm Microdul.

Matter explained some of the issues: “We don’t always know what voltage is coming off the piezo: press it slowly and you get a low voltage, bang it with a hammer and you get a high voltage. We have dealt with this and we are getting something like 10-20µJ out of the power conditioner.”

So far this gives the finger-powered wireless technology demonstrator a range of 1m.

“We want to get 50-80µJ and we are quite sure we can get it as we can improve the efficiency of the power management by a factor of between two and 10,” said Matter.

wireless piezo switchGerman finger-powered light switch firm EnOcean, which uses electromagnetic generation, has a several patents on its technology, including one patent which it has been claimed covers many or all practical mechanically-powered self-generating wireless nodes.

A contrary view is that this patent would not survive legal challenge in Europe because it can be read to cover even hydro-electric power stations, and is therefore too broad to be valid.

“We are aware of the patent and are sure the patent will never be strong enough to be approved,” said Matter.

What advantages does the Algra technology offer?

“An important aspect of the system is that we are using a piezo switch that we have been using for 20 years already so that it is very much approved and is used in thousands of application already,” said Matter. “We are making a switch with nearly no movement, so there is no metal fatigue, and there is still enough power to generate a wireless signal.”

To develop finished products, Algra is seeking application partners for both finance and expert market knowledge.

“We are a switch manufacturer and not a building control specialist. Partners will have an exclusive right to use the products, and we will get their knowledge of the demands of their market,” explained Matter.

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