Compass data error w/screenshot

MavProPlat1968 · May 2, 2019

@sar104 I will post a couple more from the same timeframe for you to look at when I get home this evening, I’ll also post the one from my crash Sunday, interested to see the results of that one.

sar104 · May 2, 2019

MavProPlat1968 said:
At this point all this stuff is new to me, so if I’m being honest I really don’t have a clue what all that means, but it doesnt look real good. Could this be a damaged compass from my crash? And this may sound like a dumb question to you, but when I took the drone apart to replace the gimbal ribbon cable, I put all of the small screws in one of those magnetic bowls so I wouldn’t lose them. When putting them back in they were magnetic because they were sticking to my non magnetic screw driver. Could that be an issue?

That will absolutely cause this kind of issue if any of those screws are close to a compass module. I recommend removing and demagnetizing them, then reassemble and recalibrate the compasses.

MavProPlat1968 · May 2, 2019

sar104 said:
That will absolutely cause this kind of issue if any of those screws are close to a compass module. I recommend removing and demagnetizing them, then reassemble and recalibrate the compasses.

Ok...I'll have to get a demagnetizer and give it a try. Any demagnitizer you recommend?

sar104 · May 2, 2019

MavProPlat1968 said:
Ok...I'll have to get a demagnetizer and give it a try. Any demagnitizer you recommend?

The CFixer is popular, but rather overpriced. You can get perfectly good demagnetizers from Amazon - I've used one of these for years.

MavProPlat1968 · May 3, 2019

Ok folks, here is a Screen record I made today while watching my compass. Any ideas what this could be. If I fly out 10 times and do RTH it will do this 10 times. As soon as it says landing the error pops up then disappears. I’ll attatch a screenshot of the error.

sar104 · May 4, 2019

MavProPlat1968 said:
Ok folks, here is a Screen record I made today while watching my compass. Any ideas what this could be. If I fly out 10 times and do RTH it will do this 10 times. As soon as it says landing the error pops up then disappears. I’ll attatch a screenshot of the error.

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View attachment 71348

I thought that we had established a likely cause.

MavProPlat1968 · May 4, 2019

sar104 said:
I thought that we had established a likely cause.

I demagnatized the screws and still getting the same thing. I can fly it all day and not get the error...only time it happens is when it starts to decend after a RTH. Also, after soldering the wire on the compass, I dont have the magnetic interference problems I was constantly getting.

sar104 · May 4, 2019

MavProPlat1968 said:
I demagnatized the screws and still getting the same thing. I can fly it all day and not get the error...only time it happens is when it starts to decend after a RTH. Also, after soldering the wire on the compass, I dont have the magnetic interference problems I was constantly getting.

So is that absolutely consistent - only on RTH descent? Because in the flight log you posted previously, any other issues were overwhelmed by the mag_mod issues. I'd suggest posting another log file after you attempted demagnetizing. Until that is fixed everything else is uncertain.

MavProPlat1968 · May 4, 2019

sar104 said:
So is that absolutely consistent - only on RTH descent? Because in the flight log you posted previously, any other issues were overwhelmed by the mag_mod issues. I'd suggest posting another log file after you attempted demagnetizing. Until that is fixed everything else is uncertain.

It does it every time on return to home decent...just after it says "landing" only flashes for a split second then back to normal. I'll post the flight log for the flight in the video, it's the only flight since I used the demag on the screws.

MavProPlat1968 · May 4, 2019

@sar104 here are a couple of dat files from today, I think the 108 is the flight from the video, the other, I was just running it back and forth a bit. Let me know if you see any difference from the other I posted...I sure don't have a clue how to read these things lol. I don't even know how to get it to show the graph like you posted from my previous log.

BudWalker · May 4, 2019

MavProPlat1968 said:
@sar104 here are a couple of dat files from today, I think the 108 is the flight from the video, the other, I was just running it back and forth a bit. Let me know if you see any difference from the other I posted...I sure don't have a clue how to read these things lol. I don't even know how to get it to show the graph like you posted from my previous log.

Neither of these .DATs match the YouTube you submitted. FLY108 doesn't have a motorStart. Here is the path for FLY109.

For the flight in the YouTube it appears that the compass problem is coincident with the gimbal pitch down that happened at 1:41 in the video. It was just compass2 that had a problem and it is close to the gimbal. Compass1 is in the back of the MP. Do you normally point the camera down when an RTH is performed?

MavProPlat1968 · May 4, 2019

BudWalker said:
Neither of these .DATs match the YouTube you submitted. FLY108 doesn't have a motorStart. Here is the path for FLY109.
View attachment 71431

For the flight in the YouTube it appears that the compass problem is coincident with the gimbal pitch down that happened at 1:41 in the video. It was just compass2 that had a problem and it is close to the gimbal. Compass1 is in the back of the MP. Do you normally point the camera down when an RTH is performed?

I normally do....I will go right now and fly basically the same path and leave the gimble up and not move it and see if I get the error
.

BudWalker · May 4, 2019

MavProPlat1968 said:
I normally do....I will go right now and fly basically the same path and leave the gimble up and not move it and see if I get the error
.

You could also try a non-flight test. Just leave it on the ground and do a couple of up/down cycles on the gimbal while watching the compass screen.

BudWalker · May 4, 2019

I just tried the non-flight test described in the previous post. The magnetic interference does increase when the gimbal is pointed down as well as pointed up. Not enough to request a compass calibration though.

MavProPlat1968 · May 4, 2019

BudWalker said:
You could also try a non-flight test. Just leave it on the ground and do a couple of up/down cycles on the gimbal while watching the compass screen.

I actually just did 3 quick out and back flights, 2 leaving the gimble facing straight forward, and one facing down....you are 100% correct, first 2 no error at all, the other with it pointing down, I got the error. Now...what is causing it lol.

MavProPlat1968 · May 4, 2019

BudWalker said:
I just tried the non-flight test described in the previous post. The magnetic interference does increase when the gimbal is pointed down as well as pointed up. Not enough to request a compass calibration though.

Did you open the screenshot that is in the same post as my video that shows the actual error I'm getting?

sar104 · May 4, 2019

MavProPlat1968 said:
I actually just did 3 quick out and back flights, 2 leaving the gimble facing straight forward, and one facing down....you are 100% correct, first 2 no error at all, the other with it pointing down, I got the error. Now...what is causing it lol.

That suggests that the compass issue possibly happens when the FC rolls the gimbal to look down before descending. That doesn't necessarily explain the mag_mod variation with yaw though - unless the gimbal pitch changes happened to correspond with the yaw changes. The gimbal pitch is not in the DAT file - can you post the txt log corresponding to the DAT file FLY084.DAT?

BudWalker · May 4, 2019

MavProPlat1968 said:
Did you open the screenshot that is in the same post as my video that shows the actual error I'm getting?

Same screen, but mine doesn't make it to red.

Do the screws that were magnetized move with the gimbal? If so, they're probably still magnetized just enough to cause the interference to indicate red.

MavProPlat1968 · May 4, 2019

BudWalker said:
Same screen, but mine doesn't make it to red.

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Do the screws that were magnetized move with the gimbal? If so, they're probably still magnetized just enough to cause the interference to indicate red.

I put all the screws in the magnetic bowl so I wouldn't lose them, I guess I'll take it back apart and pull the 4 screws up front that hold the gimble from the inside, and try to demag those and see if that helps. I was suspecting compass 1 but now that I actually have an idea what I'm looking at, I see it is actually doing great. I thought at first it was bad because it didn't have hardly any green in the line out from it, and now I realize less is better. Gonna get the yard mowed before the rain starts then I will take the screws out and try that, if that doesn't fix it maybe the small screws in the gimbal covers as well....actually, since it only does it when the back side of the gimbal is facing up towards the compass, maybe those are the issue.

BudWalker · May 4, 2019

MavProPlat1968 said:
I put all the screws in the magnetic bowl so I wouldn't lose them, I guess I'll take it back apart and pull the 4 screws up front that hold the gimble from the inside, and try to demag those and see if that helps. I was suspecting compass 1 but now that I actually have an idea what I'm looking at, I see it is actually doing great. I thought at first it was bad because it didn't have hardly any green in the line out from it, and now I realize less is better. Gonna get the yard mowed before the rain starts then I will take the screws out and try that, if that doesn't fix it maybe the small screws in the gimbal covers as well....actually, since it only does it when the back side of the gimbal is facing up towards the compass, maybe those are the issue.

Can you use the de-magnetizer without removing the screws?

You could also just ignore the problem. Usually, Compass1 is the one being used and the problem is with Compass2. Don't know that I'd accept the risk... But, then again, I might.