Heart meter

Making a simple wrist heart meter as a present for a friend, figured I would ask if anyone here might be interested in buying one, since I have to buy parts anyways.

I still need to test everything, but I'll probably be ordering parts soon. Basic design is an IR reflectance pulse meter (it does spo2 as well) with an mcu that blinks an LED with your heart beat. Nothing too fancy. If I've done the math right it should work for 50 hours or so between charges. Everything open-source.

Parts come out to around $20 give or take, give me $20 and s/h plus whatever you think my time putting it together is worth and I'll send you one.

Here's a picture of the PCB with dimensions in inches. The battery is small as well. Production time is variable, if everything I designed works first try, I'll have these out in a few weeks, but if there are issues it'll take a bit longer to make revisions.



  • I'm interested, how would I charge it?
  • It has an integrated charge controller, and uses your standard MicroUSB (phone cable).
  • The sensor I'm using came in today, time to get it on a breadboard and start building a library for it.

  • edited February 2016
    is it to be simply held to the skin? Also, what kind of sensor is that, if you don't mind sharing?
  • So, do you have a case for it? or is it just going to be open circuitry?
  • @Rytcd It's the MAX30100, a low power pulse and oximetry sensor.
    It could be held to the skin, but ideally a layer of transparent material would go underneath.

    @TheGreyKnight I'm making an enclosure for the one I'm using out of thermoplastic and thinner clear plastic, but whatever your enclosure is is up to you.

  • Does it log anything?
  • Not as it's currently designed, but I'm trying to design it to be compatible with the normal arduino IDE for ease of extension.
  • That's hilarious. I've been looking at exactly this sensor, used with an arduino IDE, on a board I'm working on as well, but there is no information I have yet found on it. There's no datasheet, no application manual, no resources, etc. I'd obviously be really interested in whatever you come up with, if you are eager to share.

    Good luck!
  • The page at Maxim has the datasheet https://datasheets.maximintegrated.com/en/ds/MAX30100.pdf
    So far I've modified my landing pattern twice after making boards with pads that were just unworkable after milling.
    I'll definitely share whatever code I make as well as board files etc, I really don't like to leave things closed source.
  • omg, I've been looking all over (including on that website) for this. The page I was looking at said it required a Non-disclosure agreement to even view! Cheers mate, I'll likewise share my progress.
  • Great, hope to hear from you. I'll be putting together an arduino library once I get it to stick to a PCB properly, and I'll throw that on github. If you're familiar, feel free to message me your github username and I'll add you as a collaborator.
  • Sensor works. Now one getting it to work at very low power algorithmically.
  • That picture is at the lowest sample rate, by the way, here's the second lowest.

  • https://github.com/kontakt/MAX30100/

    Library is posted on github if anyone is interested.
  • The library makes sense, however could you post your visualization code? I'm a little confused on HR gets read and was hoping to see your loop() function.
  • Yeah I will have examples once they're finished.
    Those pictures are a visualization of the standard deviation squared.
    This is just the basic library outputting raw data.
    You need to call readSensor() and then you can use HR to get access the datapoint.
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