Sunday, 5 October 2014

The Payload Assemblage

The new components required new arrangement. The HTC was left out this time, but I had a cable with the transmitter sticking out in the middle of the box and a handful of wires and electronics to layout in a serviceable way. The main material I used was polystyrene and the masking tape.
I began by underlaying the NTX2 by a piece of polystyrene. With the antenna pushed inside the incisions, the cable with the transmitter would stick a few centimeters above the box's floor.
The piece would nicely secure the datalogger as well with the probe sticking out of the box about 5 centimeters.
For the batteries, I prepared a whole casing to make them secure and not flying around the box.
The battery box went to one side and another piece of polystyrene, this time underlaying the transmitter from the other side, would secure it in place. Another piece of polystyrene topping at the same height as the battery box covered the datalogger.
Then I added two more pieces of polystyrene to congest the area a little bit more. One went to separate the datalogger from the remaining electronics and the other was placed to push against the previous one and the camera's frame to secure it all in place. This arrangement created a small convenient room for all the electronics. All the heat generated by them would thus be concentrated in this small area. Moreover, the datalogger alongside which some cold air could get in was separated.
All the electronics were connected. At this stage during the actual balloon flight, I would have to turn on the camera and then finish sealing the payload, because I wouldn't have access to the camera later. This meant a few minutes of camera time wasted, so it would be convenient to do it as fast as possible.
And here, all the electronics are in place. Notice that I separated the transmitter from the GPS module and the Arduino by yet another thin polystyrene piece. This was to make sure there wouldn't be any unintended current shortages. I also cut out a little space for the GPS's antenna in one of the polystyrene blocks. To secure the Arduino in place, I used a few of its own pins and simply pierced them through the polystyrene. I also turned the Arduino to face me with the power and ground pins, so they were easily accessible when connecting the battery wires. The camera got covered with a piece of foam, and the remaining block of polystyrene was used to enclose this space from above. After this stage, the payload only waited to be covered by the two main lids.
With the new parts, the whole set had to be re-weighted. After a couple more measures, the final weight settled on 940g. The HTC took some weight off, but primarily the battery pack added it all back.
The time for the last test had come.
I practiced the whole assembly including turning on all the electronics. Then I hung the payload on a nearby tree and periodically checked the signal reception. All went fine for a sufficiently long time, so my payload was finally ready to go.

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