Heart Rate Monitor (HRM) Receiver

HRM Receiver

Circuit Description

Schematic (.pdf)

FAQ

The design of this Heart Rate Monitor (HRM) receiver grew out of a desire to interface a wireless HRM to some of my other projects. Commercial HRM transmitters are available from several manufacturers. The HRM receiver described here allows these transmitters to be interfaced to a small microcontroller or PC. Here's another of my projects, Handy Board HRM, that demonstrates how to interface this receiver to a Handy Board microcontroller.

The HRM receiver is built on a 2.5 x 1.8 inch printed circuit board. It can be interfaced to just about any microcontroller that has an analog input. It will operate from the same 5V supply that powers the microcontroller. With each heart beat signal it receives from a wireless HRM transmitter, it outputs an analog pulse. These pulses are typically sampled with a microcontroller ADC port.

HRM Transmitter

This wireless HRM transmitter was manufactured by Polar, who claims to be the world's leading producer of wireless HRM equipment. Cardiosport and Sports Instruments manufacture similar equipment.

These transmitters are worn around the chest and generate a 5kHz magnetic pulse with each heart beat they detect. The transmitted magnetic signals are fairly weak, but typically have a range of over 3 feet.

These HRM transmitters can be purchased for as little as $40 (USD), or along with a no frills wrist style receiver for around $50 (USD).

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