These cameras use a CHDK script to sense a +5V signal in
their mini USB. Usually, the script causes the camera to
take a picture, but other features can be coded into the
camera’s script. Finally, note that the Camera Port is not
just for cameras. Any device requiring a switch closure or
a five volt signal to operate can replace a camera.
The tracker half of the UltraLight is a Tiny Trak 3 by
Byonics. Byon Garrabrant has obviously put a lot of care
into the design of the Tiny Trak 3. It’s a bullet-proof,
transmit only terminal node controller (TNC) that takes
GPS data, reformats it for APRS, and then keys the radio
and sends the appropriate tones. Since the PICAXE and
Tiny Trak 3 run parallel to each other, only a failure of the
GPS or main power is going to bring the mission to an
early end. So, don’t worry if you made an error in your
flight code; you’ll get your near spacecraft back to fly
another day. The 2N3904 transistor between the Tiny Trak
and the transmitter inverts the press-to-talk signal from the
Tiny Trak. This is necessary to properly key up the BM1HT
transmitter. The radio is transmit-only wide band FM and
produces a 400 m W signal. The near spacecraft’s antenna
attaches to the SMA connector next it.
There are two other ICs onboard the UltraLight. The
first is a 24LC256 (or other similar IC) with a 32 Kb
memory (operating over an I2C network) for storing flight
data. Since the Tiny Trak 3 is not used to telemeter
science data, that data is stored onboard the flight
computer and downloaded after recovery. This ensures
your mission data is clean — you don’t have to edit out
90% of the position reports in an APRS log just to get
your science results. The last IC is the MAX232. This IC
inverts the GPS data for the PICAXE-28X1. Without this
inversion, the flight computer is not able to take
advantage of the HSERIN command.
You should be getting the impression the NearSpace
UltraLight is a basic near space flight computer, but still very
capable. Those groups new to the near space field will find
that the UltraLight makes a perfect first flight computer.
■ The parts placement for the NearSpace UltraLight
CONSTRUCTING THE ULTRALIGHT
Start by acquiring the components listed in the
acquire the parts for
make a single-sided
PCB from the
pattern available in
the download on the Nuts & Volts website.
■ This is what the mounted male DB- 9 will look like on
your UltraLight flight computer.
■ Two down and
seven more to go. It
makes installing the
DB- 9 into the PCB
easier if the cut
resistor leads are not
all the same length.
So, don’t trim them
until after you’ve
soldered the DB- 9 to
the UltraLight PCB.
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