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After checking out a few projects involving IR heart monitors, I decided to have a go at the interface myself. Seen above are the results of my first experimentation with pulse oximetry. Getting the setup up and running satisfactorily required a bit more time and tinkering than I’d expected – especially after reversing a premature mod to my emitter/detector pair. The next version I try will either use a higher output emitter (see Charles Martin’s version) or
some amplification hardware (as used in Meng Li’s sensor).

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Heartbeat MIDI controller

Collin Cunningham

Collin Cunningham

Born, drew a lot, made video, made music on 4-track, then computer, more songwriting, met future wife, went to art school for video major, made websites, toured in a band, worked as web media tech, discovered electronics, taught myself electronics, blogged about DIY electronics, made web videos about electronics and made music for them … and I still do!

  • Maker Dino

    Hey Colin… nice work there. I made the same mistake with IR LEDs once. It turns out that black reflects IR light like crazy! I discovered this when building a Multi-Touch table. I had taped the edges where the IR LEDs were with black electrical tape. I had so much IR scattered light that it totally flooded the camera with IR light.

    Looking forward to what can be done with this nifty little circuit!

  • João Silva

    Many thanks for the tip on _not_ covering the IR emitter and detector. I’m thinking on using IR for communication, and I guess the effect would be the same…

  • chris

    But the size of an larger ipod and something with a speakerphone that runs off 9 volt battery. I want to hear my heart throughout the day as well as let others hear my heart. I have anxiety issues and this would help me regulate my heart better. Commerical heart monitors that make a audible beep cost 300+ dollars. Let’s make it chromey and clear plastic, call it I Heart.

  • Ronny

    Dont know if it will help, but to increase output, choose an IR LED that is high optical power, and then drive it at its highest rated continous power, and there is diodes with greater light output than the one used, shouldnt cost much more. Usually 40-50mA is no problem, but also take in consideration what forward voltage the LED have at that power, for 940nm its about 1.4V. From the examples above the LED is just about 14mA, try using a 68-82 ohm resistor instead, that will be about 50mA thru the diode, and way more light(5V-1.4V =1.6V/68ohm =52mA). Another thing is to increase the resistor thats on the detector side, the voltage swing will increase but the current load will decrease so depending on components and measuring it might be a problem.

    Dont know which is more effective for the purpose, but try using 880nm instead of 940nm, might be more effective for the purpose.


    Hey Colin
    Great Job…I’m definitely going to have to play with this one.
    Along time ago, in a valley far, far away, a fellow geek built kits for s100 bus computers…(ever seen one?)
    Steve Ciarcia ( a multi channel brain wave monitor that you could use for self hypnosis training, among other things…
    This could definitly be a cool arduino project…especially coupling it with the heart beat monitor…

  • Mudassar

    I am trying to plot about same data through com port as a plot on pc and succeded with matlab but i want to plot like yours. can you help me?

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