Heart rate monitoring system

An open-source heart rate monitoring system based on the photoplethysmography principle.

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This project is about constructing a portable heart rate monitor system based on the principle of photoplethysmography. It uses infra-red light to measure blood flow pulsations in skin, which are correlated to the heart beats. The measured pulses are amplified and filetered, and later processed by a microcontroller to compute the heart beat rate. The output is displayed on an OLED display as well as relayed to a nearby PC, tablet, or cellphone through Bluetooth.

System design of the project.

The following video describes the functional block diagram of this project.

  • Selection of microcontroller

    Rajendra Bhatt08/20/2014 at 02:52 0 comments

    The ADC block and microprocessor in the system design (described earlier) will be replaced by a single microcontroller with built-in ADC. This will simplify the design and reduce the cost. I am still debating with myself about choosing between the Arduino and PIC32 microcontroller.

  • Filtering and amplifying raw PPG signal

    Rajendra Bhatt08/20/2014 at 02:48 0 comments

    Filtering and amplification of the raw PPG signal is required to match the signal characteristics with the ADC specifications. I am currently working on an operational amplifier based active band pass filter to get rid of noise and boost the PPG signal. I will update this section soon.

  • Testing the HRM-2511E sensor

    Rajendra Bhatt08/20/2014 at 02:43 0 comments

    I quickly setup a simple biasing circuit on a breadboard to check the raw pulse signal from the HRM-2511E sensor. Here's my circuit setup for this test.

    I observed the waveform of the raw pulse signal output (Vout) from fingertip on my PC using my Analog Discovery tool from Digilent. The pulse signal waveform has amplitude of a few millivolts as shown below. This waveform was generated by wearing the sensor on my index finger.

  • Sensor selection

    Rajendra Bhatt08/20/2014 at 02:16 0 comments

    I am going to use the HRM-2511E fingertip pulse sensor manufactured by Kyoto Electronic Co., China in the prototype of this project. I have worked with this sensor before and I have found it very easy to use, and provides stable output. The HRM-2511E sensor body is built with flexible Silicone rubber material that fits nicely on the top of a finger. Inside the sensor case, an IR LED and a photodetector are placed on two opposite sides and are facing each other. The necessary connections to the LED and photodiode pins are available through a 3.5mm stereo audio connector.

    HRM-2511E pulse sensor

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