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Next-Generation Sensor Increases Smartwatch Battery Life by Five Times

Nearly 50 million smartwatches were sold worldwide in 2016, and this number is expected to grow to 150 million by 2021. Features like a step counter, altimeter, and GPS require sensors with varying energy needs. Nearly 80% of the battery power in smartwatches is used up by the heart-rate monitor. Now, a new generation of 'dynamic photodiode' sensors developed by EPFL startup ActLight can measure the wearer's pulse with the same precision while consuming only one-fifth of the energy. They have been tested and calibrated, and are now ready to be mass-produced for use in new models. The secret behind the energy-saving sensors lies in signal processing.For most sensors in smartwatches, two diodes are located on the back of the device -nestled against the wrist - which emit light that penetrates the upper layers of the skin, and blood flow determines how much light is reflected back. A sensor placed between the diodes detects these light waves and transforms the information into electrical current, which is then translated into the pulse displayed on the watch. Instead of converting the light into a current and then measuring the current's amplitude, ActLight's dynamic photodiode sensors turn the current back into light. The sensors use the pulse of light to identify the moment at which the current is triggered.

Topics:
Electronics & Computers Internet of Things Medical Monitoring Optics Patient Monitoring Photonics Semiconductors & ICs Sensors Software Test & Measurement

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    Transcript

    00:00:04 with this project we are developing heart rate monitor having extremely low power consumption existing prototypes show five times less power consumption it mean that in case of smart watch the battery will last five time longer compared to what exists now the optical sensor today are generating what we call current it's an optical current and this

    00:00:29 need more power consumption to handle the signal the one we are realizing is generating a kind of time it mean the uh the signal is simply by counting the delay and this uh need less power consumption to get the same data advantage of this approach is that output signal is directly digital performance of detector became much better because we don't have noise

    00:00:58 related to the circuits and also our device are much cheaper because uh we are using less silicon area