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How can I design a signal conditioning unit for the Raspberry Pi? [message #165097] Sat, 06 February 2016 20:44 Go to next message
messages@element14.co
Messages: 563
Registered: March 2013
Senior 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?   Original article at https://www.element14.com/community/message/173725?tstart=0#173725.

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Re: How can I design a signal conditioning unit for the Raspberry Pi? [message #165104 is a reply to message #165097] Sat, 06 February 2016 23:21 Go to previous messageGo to next message
messages@element14.co
Messages: 563
Registered: March 2013
Senior Member
This shows how to build Heart rate measurement from fingertip - Embedded Lab even tho it uses a PIC MCUOriginal article at https://www.element14.com/community/message/173789?tstart=0#173789.

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Re: How can I design a signal conditioning unit for the Raspberry Pi? [message #165109 is a reply to message #165097] Sun, 07 February 2016 10:34 Go to previous message
messages@element14.co
Messages: 563
Registered: March 2013
Senior Member
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.Original article at https://www.element14.com/community/message/173806?tstart=0#173806.

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