DIY Heart Rate Monitor


During exercise, the heart rate increases to meet the body's demand for oxygen and energy. While during rest periods, the heart rate decreases as the body requires less energy and oxygen. Recently, I went hiking to get some fresh air and felt myself experiencing a rapid heart rate during the exercise. Curious about my heart rate then, I searched through my belongings and found a heart rate sensor. With the sensor, I decided to create a DIY heart rate monitor that would allow me to measure my heart rate during various physical activities.

1 ESP32-C3 Development Board
1 Heart Rate and Oximeter Sensor
1 0.91" OLED Display
1 Battery
1 Switch
1 3D-printed Shell

Connection Diagram

ESP32-C3 to Heart Rate and Oximeter Sensor 
3.3V to 3.3V
9 to C/R
8 to D/T


ESP32-C3 to 0.91" OLED Display
3.3V to 3.3V
9 to SCL
8 to SDA


To build the 3D model of the shell of the heart rate monitor, we need to arrange the hardware layout and measure dimensions first. Then draw the model on SolidWorks.


The shell consists of two parts, an upper part and a lower part, which are connected by a shaft. The upper part includes the top cover and the upper main body, while the lower part comprises the base plate and the lower main body.

The upper part is used to accommodate the ESP32-C3 development board and a 0.91" OLED display, and the lower part is designed to house the heart rate and oximeter sensor, battery, and switch.

Slice and print the model of the shell.

The hardware layout inside the housing is shown in the figure below.

Upper part installation:
Install the ESP32-C3 controller inside the upper main body with the Type-C interface aligned with the pre-reserved hole.


Install the OLED display on the top cover.

Solder the ESP32-C3 and the display according to the connection diagram. Then put the cover on.

Lower part installation:

Fix the heart rate sensor inside the lower main body with hot glue.

Fix the switch with hot glue, as shown in the figure below.

Please note that the lower main body is placed upside down now. Install the 3.7V battery on top of the heart rate and oximeter sensor. Then, refer to the connection diagram and carefully complete all necessary connections through the gap.

Put the base plate onto the lower main body.

Install the shaft to combine the upper and lower parts together (you can use a piece of waste material.)

You can heat the ends of the shaft to create protrusions and ensure a secure fixation.



Use Test:

Clamp the device to your finger with the fingertip placed against the sensor, so that your heart rate and blood oxygen level will show on the OLED display.

With just a little bit of exercise, my heart starts racing and my energy drains quickly, exposing my lack of regular physical activity. It's time to pull out my trusty Sports Push Buttons and get my sweat on! Let's do this!

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