2015-08-10 description of the computer

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The on-board computer as of 2015, July the 20th (click to get a full-size image).

20150719 223608.jpg

At the bottom left is the 9V battery. On the bottom right is the RockBlock satellite modem. On the breadboard, you can see, from left to right:

  • The small circuit is the BMP 180 temperature + pressure sensor breakout
  • the upper larger breakout is the GPS (from Adafruit)
  • the lower one is the SD card breakout (also from Adafruit) used for log, with the SD card inserted.
  • Quite difficult to see under the wires is the Teensy 3.1 MCU which is the master of the whole thing.
  • Even harder to see (but betrayed by a blue electrolytic decoupling capacitor) is the black block of the Recom R.78 switching voltage regulator.
  • There are a few resistors there which are the voltage divider used to condition the battery voltage output so the MCU can sense the available voltage.
  • The yellow LED at the bottom is driven directly by the rockblock through a BS270 MOSFET that you can distinguish, and is turned on when the modem sees a satellite.
  • The 3 Green / yellow / red LEDs on the upper right corner display the available voltage.
  • The upper right blue LED is a last minute addition that the MCU flashes when it has established contact with the modem through the internal serial bus.

Here and there you can see ceramic decoupling capacitors.

The sharp minds will notice that the power (red wire) from the battery is unplugged = the power is off.

The whole thing is secure by the way of rubber bands in the back of a plastic lunch box ! With some pieces of plastic foam to protect as possible against vibrations (especially for the flight test).

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