This project was first featured in an article which investigated the effects Recoil has on Muzzle Velocity, and was described in more detail in a later article. I also gave an update on the progress that's been made since the first release.

The Arduino software for this project is in the sensor_logger.ino file. It's based on the example code from Adafruit for the LIS3DH sensor.

• Adafruit LIS3DH Triple-Axis Accelerometer
• Adafruit Feather M0 Bluefruit LE
• Adalogger FeatherWing - RTC + SD
• 3.7V 500maH LiPo Battery
• 3D-printed mount

There are excellent guides available from both Adafruit and Sparkfun which explain how to wire the sensor correctly.

• Adafruit: LIS3DH Triple-Axis Accelerometer Breakout Guide
• Sparkfun: LIS3DH Hookup Guide

And another for how to setup the RTC date/time and write to the SD card.

• Adafruit: Adalogger FeatherWing Guide

After assembling the hardware, you'll need to install the software in this repo onto the Feather board. For use at the range, I recommend disabling the DEBUG flag by commenting out the following line:

// Enable debug logger.
// Note: Comment out before running in real-world.
#define DEBUG

When the unit is powered up, it will create a new file based on the date/time in this format:

YYYYMMDDHHmm.csv

While it's running, it stores a few seconds of acceleration data in memory before writing to disk. The write opertation can take around 10ms, which is too slow to do constantly. It does write often enough that you should not lose much data at all when powering down.

Acceleration values are in Gs, which can easily be converted to metric or imperial units.

Here's an example of the resulting data set.

There are a few variables which can be changed according to your needs.

• ACCEL_RANGE: Can be set to 2G, 4G, 8G, 16G (default: 8G)
  Greater acceleration ranges have lower sensitivity.
• ACCEL_PRECISION: Defines the number of decimal places for the acceleration output (default: 3)
• SEP: Defines the separator character for the output (default: ,)