In my case, the desire to do the project came first -- I wanted to create my own "space-ish program" and go where thousands, including elementary school classes, had gone before, by building and launching a series of high altitude balloons and taking images from the edge of the atmosphere.
But I didn't quite want to stop there. Down the line, I want to create a platform attached to the balloon that will launch a small rocket, making this a rockin' rockoon project.
If you want to see the plans, plus get a look at the extremely messy Mega-based first draft of the flight computer, check out the posts at the bottom of this message.
Coming into this, I had zero experience with Arduino, and the last time I did anything with electronics, an individual transistor was a kind of large thing. In fact, there may have been tubes involved -- I'm that old. But I bought myself a cheap starter kit from elegoo, started picking up some other bits and pieces here and there, and eventually grabbed a solder gun and got to work.
The original mega-based comp, seen in one of the images below, has now been replaced with a nano-based version that lasts much longer on a $6 power pack from Dollar General Store. I've been driving it around in my car, testing it's ability to run for hours, to correct issues in flight, and to handle a few bumps and jostling. Things are looking pretty good.
This current version of the flight computer is pretty basic. It contains only a nano clone (this one happens to be a Lafvin, because it was cheap and they soldered the pins far more neatly than I can), a catalex SD card module, a uBlox GPS module, and a BMP180 barometer. It's all currently soldered, with a minimum of good planning and a maximum of criss-crossing leads, to a bit of protoboard. There's also another tiny board with a trio of LED indicators and a buzzer that start beeping after an hour of flight to make the package easier to find on the ground.
For this first draft, that's basically it -- it's a data logger. I'm counting on a Spot satellite-based tracker to help me locate my space capsule (styrofoam minnow bucket, $2 at the local farm supply). There's a cell-based tracker (read, old Android phone) that may also help with some coordinates once it's on the ground.
In phase 2, I intend to add an APRS radio beacon.
Phase 3 will be equipped to fire the rocket (this is to be a small model rocket using standard Estes igniters, but the darn things are notoriously unreliable in cold weather, and since I want to launch around 90k feet, it's always cold weather). A transistor and a relay are the obvious bet, but there's some research on this point still to come.
Finally, in phase 4, I want to get this all down to a neat PCB once I learn exactly which components I need and have some assurance that I've got all the functionality -- and some flexibility -- required for future flights. To that end, I'm also fighting my way through KiCAD.
I've just rewritten the flight comp software, stealing heavily from Tiny GPS ++ examples. I've dumped the String library use I had in the first edition, and that seemed to solve the memory corruption errors that were setting in after prolonged recording.
My only issue at the moment is that the BMP180 has stopped working. As in ... at all. As in, trying to even initialize it with a .begin brings the whole program to a rock solid lockup in fact, if I try to even run the BMP180 examples, I get nuttin'.
#include <SFE_BMP180.h>
#include <Wire.h>
SFE_BMP180 pressure;
void setup()
{
Serial.begin(115200);
Serial.println("STARTING...");
if (pressure.begin())
Serial.println("Good!");
else
{
Serial.println("Bad!");
while(1); // Pause forever.
}
}
void loop()
{
}
Will get me "Starting" and no more. I don't get good. I don't get bad. I just get ... stopped. So that's an issue. And since I'm the one that soldered this chip to the board, I suspect I'm the issue.
In any case, it continues to be cold and snowy here, so my intentions to launch this month have pretty well been thwarted. But that's given me the chance to build, rebuild, and rebuild again. And code, and recode.
I even splurged on a Feather Express M0 and a GPS featherwing which would allow me to make a considerably smaller flight com and store the info in flash. But for now, I'm sticking with the Nano, at least through the first flight. After all, the Spot cost $99, so I'd like to see if I can get this thing back before I add another $50 worth of chips.
Right now, the flight com costs are:
Lafin Nano: $3.60
Catalex SD module: $0.97
uBlox GPS: $18.00
BMP180: $1.95
Some of those prices were reduced because I bought some items in quantity. After all, I figured I'd ruin some (and I am at least one Nano and possibly that BMP180 in the "oops" category). But throw in some PCB board and assorted wire and the price, except when you add the solder burns on my hands, is pretty low.
Anyway, if you have a clue on the BMP180 issue, that would be great. Otherwise, I'm going to keep working away, likely building another version in a nice little project box while I wait for the weather to clear. If you want to check out the project plans, or see images of the work in progress, try these links: