Nuts and Volts - July 2014

(3x3 pin). Insert the short pins of the header into the PCB and solder it into place like you did for the digital and analog receptacles.

Before soldering the DB- 9 connectors to the PCB, bolt them to the board. Use two 1/4” long spacers between the DB- 9 and the PCB, and two 1/2” long #2-56 bolts. It’s best to use a nylock (locking nylon nut) on the bolts. That way, the nuts can’t vibrate or shake loose.

One last thing. Watch that the male DB- 9 is used for the GPS port and the female DB- 9 is used for the programming port.

What if you don’t have a PC mounted DB- 9 handy? You can use a DB- 9 with solder cups if you solder short bare wires to the one. It’s easiest to prep the DB- 9 with a set of helping hands, as soldering the wires seems to be a three-handed job.

After stabilizing the DB- 9, heat one solder cup with a soldering iron and dab a bit of solder inside the cup opening. Use just enough solder to fill the cup. Cut a short wire — like a resistor lead — and use pliers or tweezers to hold the wire against the solder-filled cup. Then, reheat the cup until the solder melts and the wire is soldered to the cup. Repeat this for the remaining eight solder cups.

Solder the three relays next. These have built-in protection diodes, so they are polarized devices. The white line drawn on the relays in Figure 2 represents the pale white lettering on the side of the relay body.

Last, solder the LM2940 voltage regulator. It’s also a polarized device and installed with its heatsink facing the right side of the board. The regulator doesn’t sit flush on the PCB.

Now, the PCB is complete except for the wiring and testing. My next column will finish the BalloonSat Extreme by discussing wiring, testing, and using the flight computer in a BalloonSat.

In the meantime, you’ll want to become familiar with programming the BASIC Stamp 2pe and storing data in its memory. One unique feature of this BalloonSat flight computer is that it can record data from a GPS receiver. So, review how to read and parse serial data, as it’s needed to collect data from the GPS receiver. Speaking of GPS receivers, if you’re looking for one to use in your BalloonSat Extreme or any other near space project, make sure it’s a GPS that will report data above 60,000 feet. There are many models that stop producing position reports above this altitude and they are nearly useless for near space exploration.