This project demonstrates you how to design and build a device to measure your heart rate using our lovely Arduino!
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Step 1: Basic Information About This Project
A heart rate monitor is a personal monitoring device that allows one to
As you see in the figure Light from an LED is made incident on the human skin at say, a finger or the wrist. As the light enters the skin, it gets reflected from components like tissue, bones, veins, arteries, and so on. However, the light getting reflected from all components other than the arteries is time-invariant and contributes only to a DC level. Only light reflected from the arterial blood has a time variant (AC). A photodiode receives the reflected light and converts it to a current. The profile of the signal is referred to as a photoplethysmography or PPG signal.
Step 2: Choosing the Transmitter and Receiver LEDs
As you see in the images, these are three couples of transmitters and receivers that we can use in our project. You can choose any of them base on you're getting the best results.
Step 3: Amplification Stage
Our output from the last step is week so we need to amplify it. You can choose different methodes. But I am just using a LM368 for amplification stage as you can see in the picture.
Step 4: Filtering Stage
Now our output is amplified but as you can see it's noisy so we need filter stages. I am just using two RC stages and you can find information about this type of filter at the link below:
For this stage I recommend you to design a Low Pass Filter by yourself or using this amazing program called Filter pro by texas instrument. It's so easy to use and you can download it from the link below:
Step 5: Connecting to Arduino
Now it's time to hook up the board to Arduino, you can choose every type of Arduino because we only need one Analog input for getting the data.
In this project I used Arduino pro min(because it's cheap). As you can see in the picture you must to connect the output to one of the Arduino's Analog pins.
You can download the Arduino code from the link below(everything is explained in detail):
now you can see the data in serial port.
For visualizing the data you can use the processing. You can download the processing code from the link below:
Everything about this stage is explained in detail at the two links above.
Step 6: Final Step
At Final step you can see the whole circuit.