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By avdlingen
#405638
Hello Org,

I just finished my home made variometer and wanted to share it with you. I based it on a Samsung Note 4 with extended battery pack (9600 mAh), connected via bluetooth to a bluefly variometer that has the experimental airspeed sensor soldered onto it. The sensor is a widely available MS4525DO sensor which is mainly used by the RC community. The Samsung Note 4 is supposed to have the best sunlight-readable screen around. I got XCsoar to use the airspeed data and did a quick check on the pitot tube which seems to give accurate readings.

I can't wait for the start of the season to do some real world tests on it!
Happy landings,
André
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User avatar
By miraclepieco
#405643
Nice job. What's the source of the case?

Pitot tube TEC (Total Energy Compensation) is essential for rigid wings, and maybe for high-end topless too, as they retain so much energy that results in a "false thermal" when one lets the bar out resulting in a climb and erroneous beeping of the vario.
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By avdlingen
#405647
If you're referring to the smartphone extended battery case, that's from ebay. If you mean the source of the actual 3D printed case that holds everything, I designed that myself.
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By avdlingen
#405659
I'll report back once I tested it in flight. About the cost;
The Samsung Note 4 (new on ebay) was €220
The extended battery was approx €40
The pitot was approx €40
The Bluefly bluetooth vario was approx €60
The flexible gooseneck was approx €10
The 3D printed case was free for me and uses about €6 worth of PLA filament
A thread adapter and some nuts, bolts and glue

That adds up to about €400
By NateHallahan
#405685
I have a similar setup, but your case is much nicer than my folded kydex case and mount. I don't have an external battery for the phone and I haven't had to worry about it running out. The sim card is removed so that might conserve battery.

The air speed used to be accurate but now it is a few mph slow. Unless my trim speed really is 13mph. I think it could be calibrated by keeping it out of the wind when you turn it on but I haven't tried it or rechecked its accuracy with a car ride.
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By avdlingen
#405694
Nate,
Your setup looks very functional and that's what matters most. You should indeed turn the Bluefly on in nil wind conditions, otherwise it will give you wrong readings. There is another way to reset this but I didn't remember how because restarting the bluefly seemed like the easiest fix.

Are you content with the possibilities of XCsoar and the accuracy and speed of the bluefly barometer and pitot? Assuming it was calibrated correctly ofcourse.

Which parameters did you choose to show in the XCsoar screen?
By NateHallahan
#405718
I've attached a random crappy screenshot from a replay. There's a lot of options to choose from but I find I don't look at the screen very much. When I do its at the flight duration and altitude. What's not showing in the screenshot is a bar that shows the arrival altitude difference to the next turn point or LZ which is good to know. Also there a circular graph that shows where the strongest climbs are in your last circle.

Keep in mind I haven't flown cross country yet but I'm confident this is a great tool, I've used it for about 30 hours. I did a lot of testing with it in the Condor 2 sailplane simulator to figure out what I wanted displayed. Spend some time going through menus and different screens while using a simulator, it could be confusing or distracting in actual flight.

The bluefly vario also works great, I tested it side by side with an Oudi and a flytec (don't remember the model) and they all sang together. I know someone else that flies with the bluefly in his harness pocket.

With the airspeed calibrated and polar data entered, XCSoar will easily tell you wind speed and direction, speeds to fly, and other fun stuff that will assist in XC flights. I have no intention of buying a vario or other navigation devices. I may upgrade the phone and case at some point.

Have fun!
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