Energy-harvesting magnetic sensors by POSITAL remove need for backup power

POSITAL's Wiegand assemblies harvest power in an efficient, innovative way.

Businesses continue to benefit from POSITAL’s famed Wiegand assemblies in many ways. They serve as a compact, efficient means of harvesting power for electronic circuits in electromechanical devices – which eliminates the need for backup batteries. These energy-harvesting magnetic sensors have been proven in many applications over the years, including access cards, encoders, and water meters.

A simple operating principle

Wiegand modules operate on a simple principle: when a Wiegand wire – a short length of specially prepared vanadium-iron-cobalt wire – is exposed to a changing external magnetic field, it keeps its original magnetic polarity, then abruptly flips the polarity when the change to the field reaches a specific threshold. This change induces a short-lived current pulse in a copper coil around the vanadium-iron-cobalt core, and the harvested energy from the magnet’s mechanical movement can be captured and used to activate a low-power electronic circuit.

What distinguishes the Wiegand effect in these energy-harvesting magnetic sensors is that the amount of electric power generated with each reversal of the magnetic polarization is constant and fully independent of the rate of change of the external magnetic field. Companies have used Wiegand modules to power rotation counters reliably in multi-turn rotary encoders, gas and water meters, and millions of other devices.

A core component in POSITAL’s IXARC multi-turn absolute rotary encoders, Wiegand assemblies offer a zero-maintenance means of powering the counter that records the amount of full rotations of the device. For other manufacturers, the company offers Wiegand energy-harvesting magnetic sensors that have 15-millimetre lengths of Wiegand wire surrounded by copper coils, all in SMD-mountable plastic structures.

POSITAL acquired the original Wiegand wire-conditioning machinery and intellectual property in 2013. Since then, the company has had a reliable supply of Wiegand wire and been able to refine the manufacturing process for higher product quality. Today, POSITAL can produce wires that reliably generate 190 nanojoules of energy at seven volts with each polarity flip.

Wiegand assemblies always benefit users that require inexpensive, maintenance-free, battery-free energy-harvesting systems for electronic counters and other low-power devices.

For more information, contact POSITAL.

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