High Altitude Balloon Project

Back in town.

Nick, how goes the electronics?

Did you get the TTRS adapter to work for you? Did mine a few months back and it doesn’t work… Think there might be too much static in the line and it just trips the VOX.

Meeting tonight at 7pm.

I called ZFW, who is apparently the correct FAA entity (i.e., not North Texas FSDO). I was told that:

  • We should call 1-2 weeks before launch, gave me a guy and a number to call
  • They split the area into sectors, and we need to call whoever runs the sector; the guy I was given apparently is good for NE of Dallas for that prairie area we’ve looked at, but if we want a different launch site we might need to call someone else
  • We are probably unregulated, but that doesn’t have to stop us from informing them
  • We probably don’t have to add a radar reflector, but he didn’t seem as sure about this
  • What we probably will do is call ZFW 30 minutes-ish before launch to inform them and … I think he said we call to update them on its altitude as well. So I think we would call at milestones like 20k ft, 30k ft, etc.
  • We don’t have any paperwork to file, or anything like that

For the attachment mechanism, I think last time we discussed going with something like 80lb fishing line instead of trying to do some elaborate paracord thing held together with lighter fishing line.

I believe we also lost the cutter FET, but that’s not a huge deal since we have about a dozen others that would only need resoldering of the wires. I also lost the NiChrome, which would be a bigger deal, except it’s like 3 bucks. This leaves shifting the Pixhawk output to a 5v on-off output via some mechanism. I haven’t looked into it a lot yet, mostly because I don’t know what Pixhawk outputs I can make work, and having to shift it with a custom something is a lot of work for something that should be off-the-shelf somewhere. (That being said, it’s the second time the on-off signal via PWM problem has come up for me, so maybe it’s worth doing some “fast” board with a PIC10 or somesuch.)

Tanner carries NiChrome wire cut to length, I noticed it there last week. Also, I could build a circuit if needed to convert the PWM output from the pixhawk to a simple on/off switch. I did exactly that for the landing light control on my RC plane. I used an ATTiny85 chip, and I still have some spare ones laying around.

If you’ve already got the circuit worked out, I’ll go with that. Main reason I wanted something off-the-shelf was because I didn’t want to spend a bunch of hours debugging a PIC10.

Running a tad late, but will be there.

Meeting tomorrow. 7pm as is tradition.

As a heads up, I am traveling out of town, and be unable to attend.

I’m going to be busy at work tonight. I will not be there.

I’m certainly interested. I’ve been talking to @wandrson about a project around an operating system for high-altitude balloons. Such an operating system would take care of the low level real time functions such as telemetry marshaling, experiment control, mode control, and digital RF communications. I’m thinking it would be based in part on the Fox-1 line of satellites by AMSAT. But, we want to be careful and avoid any ITAR or EAR issues arms “deemed” export issues.

There’s also some interest around a tracking ground station. @wandrson and I have have built alt-az rotators based heavily on the SatNOGS project. I also have a bit of software written by Andrew Koenig at UTD that will track a ballon based on its transmitted GPS coordinates and altitude. Might be a good build project, too.

@zmetzing has expressed interest in such technologies, so I’ll loop him in, too.
jb

Yup, and I actually have a picodopp kit somewhere, back when I used to chase these things in HS. Interesting thing about a canned oscillator at 11.2896MHz – the 13th harmonic is exactly in the 2m bands, and, if you apply a little filtering and a properly-sized antenna, you get a nice beacon. Add a small PIC (or Atmel, whatever) and fiddle with the voltage on the VDD pin of this oscillator and you’ll FM the tone, which is multiplied up by that same 13 … presto, tone ID and telemetry!

I don’t want to burst y’all’s bubble, but I have no clue why we’d need a custom RTOS for this. Or a custom transmitter. We’ve been designing around a Pixhawk, an APRS board from another makerspace, and (iirc) a transmitter module made for drones for a while now. Although there’s been recent discussion about switching to a Chinese Ardupilot knockoff.

Now if y’all want to fly some of your own hardware in our box, I don’t particularly mind, as long as it doesn’t require a major design overhaul. Or maybe set up a later mission that’s not geared toward a drone drop. Actually … if y’all have electronics today we could probably fly within a week. (In a sense. Not this week; I have plans and won’t be back until after New Years.)

No bubbles burst. It’s no surprise that a balloon can be launched then tracked/recovered with only simple electronics. My interest is more in using the high altitude balloon as a test platform for missions requiring greater capability.
jb

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Meeting tomorrow at 7pm. I plan to be there. General tasks are as previously listed.

I’ll be a little late. On the way now.

I won’t be able to attend tonight.

Sorry, I missed it. Had a conflict. Can you summarize the results?
jb

We got two prototypes built for the release mechanism. I ordered an APM that we will be using for telemetry and eventually automated return, but unfortunately it hasn’t arrived yet. We do have another APM on the RC desk though, and I started work on getting it to do hardware-in-the-loop simulation with xplane. The idea is that we can simulate the drop in xplane, and the APM should be able to navigate back to the LZ automatically.

Harold described the meeting well. It was just the two of us.

One thing we need to do is get Nick to leave the APRS board at the space at some point.