Infrared Heart Beat sensor

Discussion in 'Homework Help' started by Bhishma Dharmasena, Jul 17, 2017.

  1. Bhishma Dharmasena

    Thread Starter New Member

    Jul 17, 2017
    9
    1
    I have made a heart rate sensor( infrared transmitter and receiver)
    1. I need my heart rate signal to be converted into a form that the Arduino can take(5v) into its analog Input.
    2. I need to convert my signal into a pulse form
    3. I need the Arduino code to start counting the number of pulse for 1 min as soon as a button is pressed and then displaying it on a 7 segment LED or an LCD screen.
    how to do this please help me!
     
  2. muhzd

    Active Member

    May 25, 2009
    33
    3
    I'd first identify If I am getting the correct signals from the sensor counter circuit.
    I used to use the debug console to see if the variable array registers were updated correctly according to a known pulsed signal train.
    But maybe you could use terminal programs to stream your ADC values. Then you could chart the data using programs such as Microsoft Excel. See if the curves is oscillating like a heart beat.
     
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  3. Bhishma Dharmasena

    Thread Starter New Member

    Jul 17, 2017
    9
    1
    IMG_3229.JPG
    I do have the Hear rate signal clearly but I want to count them and display as beats per minute on a 7segment led using Arduino microcontroller.
    but the arduinos analog input can take in only 5v any higher voltages would damage the Arduino.
     
  4. muhzd

    Active Member

    May 25, 2009
    33
    3
    Nice shot and your desk is not looking like it is collecting dust.
    On your problem, I know no other microcontrollers that work along with higher voltages other than 5 volts. It is common though for sensor circuits to keep output signals within target microcontroller limitations.

    If you could provide the schematic, maybe other more experienced forum members could help you with this.
     
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  5. debe

    Well-Known Member

    Sep 21, 2010
    978
    192
    Its easier to just buy one of these on Ebay quite cheep at $15. PULSE-OXIMETER.JPG
     
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  6. muhzd

    Active Member

    May 25, 2009
    33
    3
    Which also makes you think if you wan't to use lower voltages. Those may be powered by just a couple of AAA batteries and so the max they supply is 3 volt. Lower system voltage requirements is desirable so it can run with a greater emphasis within battery operating voltage supply range.
     
    Last edited: Jul 17, 2017
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  7. wayneh

    Expert

    Sep 9, 2010
    13,200
    4,027
    It's easy to limit the input voltage, for instance by placing a zener diode across the inputs. What you need to square up the signal, assuming that's what you want to do, is a Schmitt trigger. That's a comparator with hysteresis, and there are other ways to accomplish the same function. Your Arduino could probably do it in code. But you could also add it externally as part of your signal conditioning.
     
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  8. Bhishma Dharmasena

    Thread Starter New Member

    Jul 17, 2017
    9
    1
    I am doing this for university final project
     
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  9. Bhishma Dharmasena

    Thread Starter New Member

    Jul 17, 2017
    9
    1
    Thank you for the reply. sorry for my late response because did not expect so much feedback.
    its a lab desk so yep no dust and here is the schematic of the heart rate sensor
    schematico.jpg
     
  10. Bhishma Dharmasena

    Thread Starter New Member

    Jul 17, 2017
    9
    1
    Thank you for your feedback
     
  11. Bhishma Dharmasena

    Thread Starter New Member

    Jul 17, 2017
    9
    1
    Thank you for your response.
    yes I do want a square signal that my Arduino can take into its analog input. wow I will look into this Schmitt trigger concept. if you find code to do this, please mail me at <SNIP> or attach it here as that would really help. ill try the zener diodes too thank you so much.

    Modertors note : removed email to avoid spam
     
    Last edited by a moderator: Jul 21, 2017 at 3:25 PM
  12. muhzd

    Active Member

    May 25, 2009
    33
    3
    If you're not going to square the signals using a zener you can instead time zero crossings. Tying input signals for the first op amp to a same specific offset (but not shorting) from ground makes your zero. And also make sure the impedance before those inverting and non-inverting pins of the op amp respective input signal points are the same.
     
    Last edited: Jul 19, 2017
  13. smatthew

    New Member

    Feb 3, 2009
    3
    0
    If this is your university final project shouldn't you be doing the work yourself, rather than asking people online to do it for you?
     
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