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  • Wrist Watch Optical Heart Rate Monitor

  • Created: Feb 11, 2016

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Heart rate monitors have been widely used nowadays not only for medical purposes but also to fitness routines. It monitors the pace of the heart especially during workout. It would be a useful tool to find the the target zone of heartbeats per minute that helps user to determine when to speed up or slow down when exercising. The portability of the device is one of its advantages since it is lightweight and wrist based which can be used anywhere possible.

The heart rate monitor is an electronic device that detects physiological parameters and converts it to a heart rate reading. It is a high performance device that effectively displays the number of times the heart beats in a minute. This device uses the TI’s AFE4400, a fully Integrated analog front end that consists of a low noise receiver channel with an integrated analog to digital converter, an LED transmit section, diagnostics for sensor and LED fault detection. Other components employed are ultra-low power microcontroller for calculating the heart rate, a wireless module based on Bluetooth Low Energy (BLE), a motion sensor for monitoring the user’s activity, a reflectance mode sensing probe, ferroelectric RAM (FRAM) for data logging, a lithium-polymer rechargeable battery, a battery charger and a battery fuel gauge. In this design, the microcontroller is used to calculate the heart rate, merge the motion sensor data, and process the AFE information. Sensors are the key elements to identify the orientation of the arm, wrist or other specific part of the body where activity monitor is located. The battery charger operates from either a USB port or ac adapter and supports charge currents up to 1.5 A. The input voltage range with input overvoltage protection supports unregulated adapters. The USB input current limit accuracy and startup sequence allow the battery charger to meet the USB-IF inrush current specification. Additionally, the input dynamic power management prevents the charger from crashing incorrectly configured USB sources. The battery fuel gauge circuits an easy-to-configure microcontroller peripheral that provides system-side fuel gauging for single-cell lithium-ion batteries.

Optical heart rate monitors are readily available in the market. However, designs differ from its performance, complexity and portability which makes this design notable. It is not only a high performance device but it has also high portability. It is well suited for health conscious people that can also be integrated and modified by electronics enthusiast as desired.



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