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.
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.
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?
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.
Alright, meet tonight at 7pm as per usual. I did speak to Nick last night, and he said he’d bring the APRS board.
So last night Harold and I worked on the Ardupilot knockoff mostly.
- Discovered pin 9 can be used as a “relay”, and there’s a way to script this in the mission planner.
- Bought 5 power MOSFETs that have a Vgs_threshold < 3V, so they can be actuated by the system voltage
- Did a bunch to get hardware-in-the-loop working; not quite there, but a lot closer
- Looked at the APRS board code, got it to compile ("#define prog_uchar unsigned char")
- Nick forgot the APRS board
- Harold couldn’t find the GPS module for the Ardupilot
- I can’t find the NiChrome I bought a while ago
So, to do:
- Get Ardupilot working
- HitL not strictly necessary, but nice to be able to test with, probably want anyway
- Program the balloon flight into the Ardupilot, pseudocode:
- “interrupt to read and broadcast APRS / telemetry data every X seconds”
- “wait for altitude = 60000ft”
- “relay on pin 9 (i.e. cutter wire) on”
- “wait for X seconds”
- “relay on pin 9 (i.e. cutter wire) off”
- Interface the Ardupilot and the APRS board
- Actually, it looks like the Tracksoar is autonomous; we should only need to provide power
- Interface the Ardupilot and whatever our secondary telemetry system is
- What is our other telemetry system, again?
- Interface with cutter
- Get APRS board working
- Get Nick to leave the board at the space
- Nick, didn’t you say you had a ham license? Someone will need one, I believe
- Finish cutter / paracord attachment method
- Redo cutter housing to be … better
- Test whole electronics system in assembled state
- Remember the GoPro
Am I forgetting anything?
Once we have the electronics worked out and the attachment system ready, we can do some flight testing on a drone, then move on to the real deal, I believe.
I’ll bring the APRS board up later this week.
Yes, I am a ham radio operator, license KD5FTN.
The APRS Transmitter is designed to be a stand-alone redundant location tracking mechanism, totally independant of the APM autopilot.
The APM autopilot radios will maintain a continuous telemetry connection with our ground-based radio. Default “air rate” is 64K, but we can reduce the data rate offset for a weaker signal and get more range. Additionally, I can use my more-sensitive ground-based radio (RFD900), which has diversity antennas. We can use high-gain antennas and aim them appropriately. (Or get fancy and build an antenna tracker)
We’ll likely also want to add a small RC receiver to the payload which we can use to both manually fly the glider and/or manually activate the nichrome trigger, if we have an RC signal.
So, we can have three potential ways to trigger the wire cut, but all dependant;
- Scripted mission, wire cuts automatically upon reaching altitude (Automatic)
- Do_Relay command sent manually via Mission Planner (Dependant on Telemetry radio link)
- Switch activated on RC transmitter (Dependent on RC signal being received).
The good thing is, bot the telemetry and RC radios will have RSSI telemetry to let us know signal strength, but we won’t know real-world range until we actually go fly this thing.
I was looking at the APRS board and noted it has its own GPS on it. Would it be feasible to get the GPS on the APRS board to interface with the Ardupilot GPS input, so that we don’t need to chase down a new GPS module?
Not unless the APRS has a GPS/Compass I2C output.