Freesteel Blog » 2016 » April

Thursday, April 28th, 2016 at 12:04 am - - Flightlogger, Hang-glide

Well, the hang-gliding has been quite lovely. But the logger appears shot to pieces.
I still don’t know what I am doing when I get to cloud-base, which is probably why I plummeted out of the sky shortly after this picture was taken.

As soon as I took off, the barometer stopped communicating most of its data.
This is the device I lavished so much time on isolating it from the rest of the electrical circuit and arranging for it to bitbash the information back through an interrupt pin.

It could be some timing issue, or whatnot. No way to debug it. Luckily I got myself a Bluefly vario which does the same thing of reading a MS5611 barometer on a tight 50Hz loop and transmitting it back to the main board. In the Bluefly’s case it’s for the purpose of running a Kobo/XCsoar system. I’ve just given up on the one I built as it’s too inferior to simply running XCSoar on the phone where I’ve got colour and more or less know how to use it.

Luckily the Bluefly also sports a GPS and works through a serial port, so I’ve yanked off the Adafruit GPS breakout board and bodged the wires to insert the Bluefly in its place.
Then there was a small matter coding it up using a complex state machine to program the GPS module through the Bluefly pic processor to get it to read at 10 times a second.

But then the BNO055 orientation sensor played up and decides to shutdown at unexplained moments for unexplained periods of time.
The white vertical lines are 10 minute intervals, and there is a green dot for every successful orientation reading, with y-value proportional to the time since the previous reading, so I’m getting gaps in the data of half an hour in flight.

I’ve produced a reset timer to try and start it off again if no data comes through for 20 seconds.

Anyways, here is one of those nerve-wracking close encounters with the ground during the flight.

Tuesday, April 19th, 2016 at 11:29 am - - Hang-glide

If you look closely you can see the grin behind the helmet.
There was nothing especially epic about this XC flight from the Long Mynd to Clee Hill, except a masterful get-away from the slope in nil-wind with just one thermal during which I miraculously stayed on top of all the paragliders. Also there was a very low-save.

I took off at about 1:30 during the period when the wind was less than 5mph and sometimes coming from the SW. This trace is off the Long Mynd Gliding Club weather station:

No one could explain why there was so little breeze to make reliable ridge soaring possible. Meanwhile, there were champion pilots flying 100s of miles on seven hour flights on that day, which one must try not to feel bad about, when I “only” managed to stay up for an hour and a half.

One thing I did learn for sure is that I utterly depend on the thermal assist of the XCSoar running on my android phone. (That Kobo kit you see in the video is going in the bin.) The magic went away when the phone ran out of batteries; my thermal tracking abilities went out the window from that moment on. So this flight (and hopefully many more, when I sort out an extra power supply brick for the phone) is dedicated to Lines 145 to 202 of XCSoar/src/Renderer/TrailRenderer.cpp which was able to direct my search for lift whenever I lost it. This is the section of the manual describing the critical feature:


A couple more regrets. I didn’t make cloudbase by at least 300m, according to the dew point measurements. And the barometric reader, based on bit-bashing and interrupts, is completely shot to pieces by the overload on the microcontroller from acquiring so many other inputs of data. Only about 1% of the readings are getting through. I’ve got to come up with some other answer, and I don’t have a lot of time in a week when we’ve got some help doing something about the state of the kitchen floor.

Monday, April 18th, 2016 at 4:43 pm - - Machining

This has taken a lot of effort fighting through the device trees on the Beaglebone to make it access the PWM and Quadrature encoder services at the same time, which is the minimum required to effect a stimulus response observation from a DC servo motor powered by an H-bridge.

What happens when you apply a fixed voltage to the DC motor for an eighth of a second, then reverse the voltage for another eighth of a second, and then set the voltage to zero (and try it for many different voltages and directions):

Here’s the graph of motor positions (in Y) over time (in X) for 20 different trials:


Wednesday, April 13th, 2016 at 12:39 pm - - Hang-glide

Thought I’d scan and upload my article about flying in Austria for folks to download:

JGTskywingsLoser.PDF (7Mb)

Individual pages:




Tuesday, April 5th, 2016 at 1:04 pm - - Flightlogger

On this second day of heavy rain in the Pyrenees I think I might have the time to catch up some ancient history from all of last week. We waited five hours on El Bosque for the wind to come right, and were then rewarded with this flight with vultures.
These birds came much closer than they ever showed up in the pictures. They fly with hunched shoulders.

Unfortunately the GPS for that flight is inexplicably jagged, so here’s a flight above Teba from a day later where the data is cleaner.



The yellow cube is 1000m on each side for scale from a flight that took off at the point on the frontmost vertical cube edge

Here’s a zoomed in section of the left most section of the path, shown looking down, with 100m XY axes in yellow. The track comes in from the bottom right goes to the top left (against the wind direction), then turns left to make four anticlockwise loops that drift back with the wind