Sensor Tag Logger

Summary

TI’s Sensor Tag consists of a smorgasbord of sensors packed on a board powered by a coin-cell battery with Bluetooth LE (ambient and IR temperature, humidity, barometer, gyroscope, accelerometer, compass in the version I had – current versions sport additional sensors).

I created a Sensor Tag Logger board as a learning exercise (schematic design, board layout, soldering, SMT, firmware, bluetooth LE). It used an Arduino Pro Mini and a Bluegiga BLE112 bluetooth module to query the Sensor Tag for appropriate data and log it to an SD card. It used an RTC for timekeeping for logging, and an interface with push buttons and LEDs that was used to toggle on/off different sensor logging. A shift register was used to help manage the IO (the project pretty much maxed out the available ports of the Arduino Pro Mini). The hardware schematic and firmware are open sourced on GitHub.

Background Context

I saw that someone had used the SensorTag to collect data from an amateur rocket launch ( iPhone Flies on a Rocket: Collect and Analyze Data! ). You had to either fly an iPhone with the rocket, or limit the data collection to at best 300 feet of flight data (the best case range for Bluetooth LE).

There are so many different scenarios under which a SensorTag can be used to collect data. In all of these cases, it would be great to untether the SensorTag from your smart phone – and let it collect data even when you are not there. Thus was born the Arduino Bluetooth LE Logger for TI Sensor Tag! It connects over Bluetooth LE (BLE) in master mode to the TI Sensor Tag, and turns on notifications for the characteristics you have selected (via push buttons), and starts logging the data to a microSD card, along with the timestamp, in a Comma-separated value (CSV) format, for easy importing into spreadsheets for additional processing and graphing.

Supplementary Links

Sensor Tag Logger firmware - https://github.com/sridharrajagopal/SensorTagLogger Sensor Tag Logger writeup with additional details - https://bayareamaker.wordpress.com/2015/09/15/arduino-bluetooth-le-logger-for-ti-sensortag-and-others/

Build Process

I learned to use Eagle CAD for schematic and board design. I also had to create custom library components. I used OSH Park to make the PCB, and hand soldered all the components (including SMT components and chips) - another learning experience!