Wednesday, June 26, 2019

Parts in the mail

A few more parts came in today --

  • Adafruit LIS3DH accelerometer breakout. I'm hoping this will be a reliable accelerometer to add to the probe, so we can choose between using aerodynamics or acceleration for yaw detection. The breakout boards are only for the LIS3DH, but we would use the LIS3DSH if we were stuffing an SMT board from scratch since it has better resolution.
  • Adafruit BMP280 barometer breakout. This is (one of the) latest Bosch barometers, and we can use that along with a 3D printed "cap" to create a cheap ported barometric pressure measurement. For our own SMT board, we might want to use a BMP388 since we seem more suited to its target market. (I should get some of the BMP388 breakout boards too.)
  • Sparkfun Pro Micro 3.3V. This will be the brains of our "breakout board" probe. You may recall we had trouble with the Sparkfun Fio V3 due to how it wires the battery to a pin on the microcontroller. This way we can avoid this issue.
  • Sparkfun LiPo charger plus. A separate battery charger.
Laying out all the required parts on a 1.5" x 5.5" grid (which is the size of our standard Airball probe board), it looks like we can fit it all with 0.1" thru-hole soldering without too much trouble. Note we are using both sides of the board, but the interference between the signals should be pretty minimal:

Of course, eventually, we'll want to put all this on an integrated SMT board, but for now this should get us started.

Initial testing with the accelerometer seems to show decent results; we'll see how it does when it's actually mounted and flown.

Our first test will not be with a complete probe but rather with just 3 pressure sensors and the accelerometer, as a focused experiment to correlate aerodynamic yaw and lateral acceleration. Stay tuned for the report of this within the next few days (I hope).

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