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Wireless body temperature monitor/logger

I have been experimenting the last couple days with a wearable electronics project – a wireless body temperature monitor/logger. The idea is to remotely monitor kids body temperature, if they are sick, and put up a status display with alarm function in our bedroom. The remote monitor will be another Funky with RGB LED for visual temperature representation and a OLED display with a piezzo buzzer to sound alarm, if the temperature goes above a threshold.  Since the transmissions are picked up by my IoT gateway and logged to emoncms, I can visualize that data remotely, including on my phone. Body temperature data is collected and transmitted wirelessly by a Funky v2 equipped with a DS18B20 temperature sensor and a CR2032 battery holder (extra flat one). I soldered a 0603 sized 4.7K resistor on the DS18B20 (required for its operation), pictured below (really miniature):IMG_2678The wires were then covered with heat shrink tube:IMG_2679

.. and the sensor soldered to Funky’s pads:IMG_2681IMG_2682

Using an extra-flat CR 2032 battery holder to make the project as thin as possible, and it measures only 9mm:IMG_2683

I weighted the complete project (with battery inserted), it measures barely 8 grams:IMG_2684

The node is running the DS18B20 sketch; I wanted to stress-test it and am sending data every 5 seconds. The final project will send once a minute.

My next challenge was to attach it to my body. I originally tried to have it on my wrist using a stretch band, but the temperature of the wrist is a bit low (normal):IMG_2686

I could add to the reading to compensate for this. I tried another place, just taping the sensor to my arm:IMG_2687 IMG_2692The temperature sensor goes under my arm.

I had it running for the day, I was doing gardening, lawn mowing and at some point was away from home. Below is a chart of the readings:body_temperature

Obviously the position of the sensor isn’t optimal, I would get all sweaty when mowing outside in the intense heat (resulting in dropped temperature readings); I even took a shower with the sensor covered with a dry towel. Measuring temperature under the arm requires it to be firmly pressed to the sensor, while I have my hands moving around all the time, resulting in falsely low readings. Maybe I need to try another location for attaching the sensor. Below is an infrared image of a human body (taken from hereThermal-Infrared

Overall interesting project with potential for use.



3 thoughts on “Wireless body temperature monitor/logger

  1. Paul

    Why not use the Event module in emoncms to set up alerts which can then be sent to your phone/pc via Prowl, instead of using a piezo sounder.
    I’m using an emontx to monitor my greenhouse temp, and have set up incremental warnings, which work reliably.

    1. Martin Post author

      I was also considering that option, but then it adds some risk of missing an alarm event if the Internet connection is down or phone battery dead and so forth. It can be added as a backup option, but for primary event notification I’d use something reliable.

  2. Ricky

    Hello Martin
    I would like to purchase your body temperature monitor
    as I need to monitor and trend my body temp while asleep
    Kind Regards
    Ricky Thomson