■ FIGURE 3. The schematic of the
BalloonSat Flight Computer, or BFC.
This schematic was created using
Proteus, a program I’ll have more
to say about in my next column.
data can be made every 35 seconds. At
a climb rate of 1,200 feet per minute to
an altitude of 85,000 feet (typical of
near space missions), data can be collected every 550 feet during ascent and
1, 100 feet (on average) during descent.
The BFC uses a
LM2940T- 5 for a voltage
regulator. Therefore, the
maximum current the
BFC can supply is one
amp. Since BalloonSat
don’t draw a lot of
current, four AAA cells
(six volts) is sufficient to
operate a BalloonSat
for several missions.
Connecting to the BFC
are cables for its
battery pack, a main
power switch, a power
indicator LED, and a
mission initiate pin.
SOLDERING THE BFC
Start assembling the BFC printed
circuit board (PCB) by soldering the
lowest lying components first, like the
flat lying resistors. Use the cut resistor
leads for the PCB’s four jumpers. To
protect the ICs from heat damage, use
IC sockets instead of soldering the ICs
directly to the PCB. Rather than
■ FIGURE 4. The placement
of parts in the BFC.
November 2006 103