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How can I design a signal conditioning unit for the Raspberry Pi?

Former Member

So I am taking on a project which involves to develop a heart rate monitor using the raspberry pi. I aim to take the signal using an IR sensor and a photo-diode sensor (like a finger sensor), and have this process using the raspberry pi. I know the Pi doesn't have an ADC. I am thinking to build a signal conditioning unit for the pi as well to treat the oncoming signal, however I am unsure of where to start this. Can anyone help me or give me some advice?  

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  • You could:

    Amplify the photo diode signal with an opamp circuit.

    Apply a low pass filter set at 2x the maximum heart rate you want to measure.

    Then

         Either apply the filtered signal to an ADC with an SPI port connected to your RPi

         Grab the signal and do some comparison and counting in software.

       

         Or apply the filtered signal to an analogue comparator to produce a logic level squared up version of the signal.

         Apply the logic signal to an IO pin of the RPi and count transitions.

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  • You could:

    Amplify the photo diode signal with an opamp circuit.

    Apply a low pass filter set at 2x the maximum heart rate you want to measure.

    Then

         Either apply the filtered signal to an ADC with an SPI port connected to your RPi

         Grab the signal and do some comparison and counting in software.

       

         Or apply the filtered signal to an analogue comparator to produce a logic level squared up version of the signal.

         Apply the logic signal to an IO pin of the RPi and count transitions.

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