Breath Monitor: battery operated and wifi enabled

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cfoxit
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Joined: Mon Jul 03, 2017 1:55 pm

Breath Monitor: battery operated and wifi enabled

Post by cfoxit » Sun Nov 12, 2017 12:37 pm

Hi all, looking for some feedback on the wiring layout of my first real project, any insight is appreciated as I'm petty new to this. I'm designing a device that will monitor when a user is inhaling/exhaling by measuring the changing voltage through conductive yarn sewn into an elastic band. Basically as the band stretches, so does the yarn, and as the yarn stretches it's surface area changes creating a changing resistance, etc.

The project has two main requirements besides reading this changing voltage; it must be portable (thus battery operated), and it must be able to send the voltage readings to a tablet via Bluetooth. With these in mind, I have gathered together the following components that I think suit my needs:
5V Arduino Pro Mini: https://www.sparkfun.com/products/11113
5V Stepup breakout: https://www.sparkfun.com/products/retired/10968
Bluetooth modem (BlueSMiRF Gold): https://www.sparkfun.com/products/12582
LiPo charger (micro USB): https://www.sparkfun.com/products/10217
LiPo battery (1000mAh): https://www.sparkfun.com/products/13813
Rocker Switch: https://www.sparkfun.com/products/8837

Below is a mockup of the layout I have planned, with all the components (minus the elastic band) to be soldered to a blank PCB board:
Image

Hopefully the image I provided is helpful in understanding what I'm going for; the LiPo sends 3.7V through the charger, where it's increased to 5V by the stepup breakout, and the rocker switch allows the rest of the components to receive power when desired. 5V from the Arduino Mini is run through the elastic band, with a third wire (in yellow) reading the analog voltage as it changes. The BlueSMiRF then will send the info off to a tablet.

The area I'm mostly questionable on is the interaction between the Arduino Mini and the BlueSMiRF. believe I've gotten the connections between the BlueSMiRF and the Arduino Mini correct, I took them based off of this guide to using the BlueSMiRF: https://learn.sparkfun.com/tutorials/us ... -bluesmirf. Due to the differences between the Arduino UNO in that article and the Arduino Mini I'm using, I thought it was necessary to provide power via one of the digital pins. This IS possible right? By setting the pin mode to HIGH to provide an output voltage? Although if I'm misinterpreting something about this or the other pin connections, please correct me! I've tried to do as much research as possible before asking others.

I know this is a long post, thanks for bearing with me. I appreciate any comments and guidance to be offered, thanks!

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