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Voltage and Current Logger

A low cost way to log voltage and current for wearable/IoT devices

I needed a low cost way to measure current requirements and battery drain over time (for one of my wearable projects). I have a TON of Adafruit Feathers and FeatherWings, so I decided to use components I already had, plus an Adafruit INA219 FeatherWing to build a voltage and current logger. It logs to SD card, Adafruit IO, and has outputs for tracking and triggering “events”

I’m in the process of building a small wearable device (the be better bracelet) and I wanted it to be as small as possible. I originally powering the wearable with a coin cell battery, but realized pretty quickly that those batteries didn’t have the required mAh for my project (which includes a haptic motor).

I needed a way to track battery life and current over time; I also wanted a way to easily trigger or record “events” (an action taken to take the project out of sleep). I didn’t want to spend a lot of money on tools, so I looked into building something leveraging one of the 20+ un-used Adafruit Feathers (and FeatherWing accessories) in my electronics toolbox.

I knew that Adafruit had a INA219 current sensor FeatherWing… so I wired that to an Cortex M0 (with an ATWINC1500) feather and a TFT device. This allows me to see updates on the screen, send readings to Adafruit IO, and record data to an SD card.

I wanted something easily portable and extendable, so I:

added a small Lipo battery to the logging device
printed an enclosed case
added an on/off rocker switch
added two 2.1mm female panel mounts: input for a battery or other power input and an output to the device I’m measuring
two banana clip female panel mounts - to either “trigger” an event (e.g. sends a HIGH output to simulate a button push) or to track an incoming event (I manually pushed a button on the wearable)”

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