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Proof Of Concept and Next Steps

A project log for LIFE+: The Human Performance Monitoring Band

An open-source performance monitoring device.

Anthony I StewartAnthony I Stewart 04/10/2018 at 03:460 Comments

This is the proof of concept for the Life+ band that I developed around the end of my first college semester last year. There's nothing special about this prototype, it contains a cheap Bluetooth module, Accelerometer/Gyroscope combo (GY-521 MPU-6050), Heart Rate sensor, (Pulse Sensor Amped) and a temperature sensor (TMP36). An Arduino Pro Mini is used as the brains of the band.

For the construction of the band itself, I decided to use craft foam I bought from my local AcMoore. I used a paper template to get the shape of the band to fit my wrist and still have a bit of room to house a battery and be secured with Velcro.

Since this band was just a proof of concept I decided not to spend too much time worrying about aesthetics, although I did choose to use red and black foam since I really like those colors!

The components were wired together according to the poorly drawn diagram below.

Once wired together they were then secured to the craft foam using hot glue which, in hindsight, might not have been the best material to make it out of. Since I didn't want the components to be shorted out accidentally, I then covered them completely in electrical tape to prevent that from happening.

Next up was finishing the enclosure for the band.

I used hot glue to secure the red piece of craft foam to the black piece that held the electronics. Two openings were cut into the craft foam. One allows access to the Arduino Pro Mini's programming headers, the other allows the plug for a 9V battery to reach the outside. 

And just like that, the proof of concept was complete! One thing to note: I decided not to use a lipo battery as I originally planned simply because I didn't want the extra charging circuity to over-complicate the design after all this was only just a proof of concept. 

The code running on the Arduino sends data from all of the onboard sensors to a connected device using a Bluetooth software serial port. The band has 2 modes, the first one sends over raw data from the heart rate sensor in addition to the rest of the data from the other sensors. The second mode sends over the BPM as calculated by the Arduino. My initial thought behind doing this was to have to have the band function primarily "offline" in the sense that it would store data locally for analysis later on, for this it would be in the BPM mode. If you were doing intense training or wanted an in-depth analysis of your vitals you would instead use the tethered mode. In this mode, the band sends over raw data to either your smartphone or other devices to handle the processing. Since those devices have more power than your average Arduino you'd be able to process data at a higher sampling rate and using more complicated tools such as machine learning.

Overall I'm happy with the way this proof of concept turned out. While it didn't demonstrate anything groundbreaking or astonishing, it did give me the insight and motivation I needed to carry this project to its next step. Now that I have a clearer idea of what I hope to accomplish next up on my list is to design a much more modular and compact design for the Life+ band. I also need to begin work on software and data encryption. Thanks for reading and keep an eye out for my next log!

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