Weekly Reports from Student High Altitude Launch and Payload Teams

Week 5: July 2 – 6, 2007

This week, testing of the UV sensors and solar panels continued, the camera system was refined, and construction of the payload structure began.

Kenion and Roderick continued work on the UV sensing system. This week they tested how the UV sensors were affected by shaking and temperature. In order the test the effect of shaking they attached the sensor to a car which one of them drove while the other recorded data. In order to test the effect of temperature a Styrofoam container was constructed. Dry ice was obtained and placed within the container along with the sensor. The apparatus was taken outside and a multimeter was used to measure the sensor reading as the temperature decreased. The temperature was measured with a standard thermocouple.

Caitlin and Chelsey soldered the interconnections between the solar panels to form the completed solar array. Large staples were obtained to secure the array to the foam exterior of the payload. The staples were coated with electrical insulation to prevent shorting. Using some of the dry ice obtained by Kenion and Roderick, the effect of temperature on the solar panel’s open circuit voltage and flexibility was informally tested.

Eric and Jon worked on the camera and electronics systems. Two servos for the camera turret were obtained: a micro servo to control the ‘tilt’ of the camera and a standard heavy duty servo (HS 322HD) to control the ‘paning’ of the turret. The poorly documented open source firmware of the CMUcam3 was studied and had to be modified to make the camera function as advertised. In order to test the operation of the CMUcam3 with the new servos, a simple turret was constructed with cardboard and electrical tape. Once the camera was made to function as advertised, the ‘paning’ servo was modified for continuous rotation. Normally, a servo receives instructions in the form of a position to which it moves upon receiving said instructions. A servo modified for continuous rotation receives instructions in the form of a speed at which it will move until receiving new instructions. The CMUcam3 firmware was designed to send position type instructions to the ‘paning’ servo so the firmware was modified so that it could track with the continuous rotation servo. In summary, the camera which could barely track light over a paning range of 90 degrees horizontal can now track over the full 360 degree range horizontal and 90 degrees azimuthal. Aside from the camera, a foam cutter was constructed and used to begin the shaping of the payload’s exterior foam battery housing/solar panel support.

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