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Maine Solder Guy

Member Since: August 28, 2006

Country: United States

  • I've worked on the medical side of this issue for decades (retired respiratory doc) Three comments: 1) The vast, vast majority of people will become obligate mouth breathers with a heart rate in the 160s. Broken nose or not, you simply can't get enough air in to sustain metabolism nose breathing when running. (That's why US football players work so hard at developing maximum muscle efficiency when doing downfield sprints-- they can't open their mouths because of the tooth guards.) 2) Thank you so much for supporting masks. A cloth or paper mask (not N95, different creature) places a minimal resistive element in the air path, particularly if mouth breathing. It may feel uncomfortable, because of retained humidity, etc. Unless you are an absolute world class athlete trying to break a world record, it won't matter that much. 3) your problems with getting a good, steady biologic signal to analyze are not surprising. This is where mechanical design is much more important than the electronics. The sensors and electronics have been around forever and simply work. Getting a good, stable attachment to the finger that will survive activity is hard (if you can keep your ears warm, consider an earlobe clip instead!) Most exercise systems also have software that does some noise and artifact rejection. Thanks for an interesting read!!

  • The DS3231 can use the 1307 libraries. I'm not sure that you extract all functionality, but my uses have been fairly simple and I don't need all bells and whistles. My major interest was the temperature controlled oscillator and high accuracy.

  • One more post: I spent a couple of hours getting the interrupt to work this morning. Two pieces of info that may be of use-- (1) The output of the square wave pin on the ds3234 cannot be tied directly to the input of an Arduino. A 4.7K resistor seemed to work fine. (2)You may need to build a delay into your code between detecting a square wave and reading the registers to let the update complete.

  • Cancel that question. Half asleep this morning. I figured it out.

  • Some help, please. I intend to use the square wave output to trigger an interrupt on a uC. The datasheet says that this line needs a pullup resistor. The schematic for the board shows a 10K resistor and 22pf cap to ground from this pin. I presume that the 10k, since it is on the "high" side of the cap, is not an issue in terms of my pullup resistor.
    So... a couple of questions from this newbie. The reference diagram on the datasheet does not indicate a need for this circuitry. Why is it there? Second, any suggestions for a pullup? I was thinking in the 4.7K range.
    Thanks all.

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