DIY rear compass cabling fix

DerekG · Feb 24, 2017

Rich Sugden M.D. said:
Something strange here ... you mention a "front" compass, and a "rear" compass ... I doubt seriously there are two compasses on the Mavik, or any device, for that matter ... unless for redundancy if one fails. No reason to have more than one.

That's exactly the reason... redundancy if one fails or starts giving bogus data like in this case

Starting with the Phantom 4 DJI has put in dual IMU as well as Compass modules. Next up (for the P5) will probably be dual GPS, as that would certainly be of benefit to some.

The Inspire 2 takes it a step further with dual barometer (for height if GPS is lost) and dual battery too :]

Mr Spock · Feb 24, 2017

flyNfrank said:
@Mr Spock

Thanks, after 10 pages of reading I now understand how this thread came about. I'd have to think that the more recent Mavic production has had this issue addressed? I fly in strong winds a lot and I tend to get the Strong Wind message box which is understandable. I never get any type of compass warnings.

Yes u r correct it appears to be a NEXT (near end crosstalk) or interference from the motor wires leaking into the rear compass sensor then the compass does not agree with the the GPS north bearing and the machine goes to ATTI mode and so on. As the guys indicate here the older models have this issue whereas the later models have twisted motor wires and this fixes the interference as signals cancel each other and there is no issue any more. U must have a later model and u can also use that SW tool that one of the guys made and u can measure to see is you have an issue or abnormal compass values at sport mode top speed maneuvering.

Mr Spock · Feb 24, 2017

Question. Do i get the DAT or txt files to use with the CSV tool ? and Do i use Assistant 2 to get the log files from the MP via the USB port or do i use the files found in the phone/tablet ? Never used ether tool before so help would be apriciated.
Also can someone post some pics on how to detach the rear legs of the MP?

Logger · Feb 24, 2017

Mr Spock said:
Question. Do i get the DAT or txt files to use with the CSV tool ? and Do i use Assistant 2 to get the log files from the MP via the USB port or do i use the files found in the phone/tablet ? Never used ether tool before so help would be apriciated.
Also can someone post some pics on how to detach the rear legs of the MP?

In this case you will want to get the DAT file from the aircraft using the DJI Assistant 2 tool via the USB port. Once you have this DAT file on your PC/Mac, open it with CsvView. Once it is in CsvView , double click on the "Empty" sigplayer to open this player and select "Add remove" signals. Select the Signals you want form the list. MagZfront, MagZrear etc.

Mr Spock · Feb 25, 2017

Logger said:
In this case you will want to get the DAT file from the aircraft using the DJI Assistant 2 tool via the USB port. Once you have this DAT file on your PC/Mac, open it with CsvView. Once it is in CsvView , double click on the "Empty" sigplayer to open this player and select "Add remove" signals. Select the Signals you want form the list. MagZfront, MagZrear etc.

Thank u Logger. And i presume i have to do a flight run with the MP in sport mode beforehand and find the DAT file corresponding to that run to check for this issue or an older DAT file from a previous flight will be still stored in the drone ?

Pedro · Feb 25, 2017

Is there any way that we can trace the point at which DJI started twisting the cables by serial number? I presume that the serial numbers are sequential..

pitchmagic · Feb 25, 2017

Ok, did a test run and get the same warning and the same numbers from Mag.Z.Back. Im taking out the screwdriver. Can someone confirm that i can twist the rear arm clockwise if I remove the torx by the end of the arm?

Highest p2p is 257;

Mr Spock · Feb 25, 2017

Can someone pls share more detailed pics or a vid on how to remove the rear arms so that we can twist them till the wires are permutated 4 times?

flyNfrank · Feb 25, 2017

Mr Spock said:
Can someone pls share more detailed pics or a vid on how to remove the rear arms so that we can twist them till the wires are permutated 4 times?

Are you referring to only twisting wires inside the arm itself?

Btw, I put this image together to help show what's going on.

Mr Spock · Feb 25, 2017

flyNfrank said:
Are you referring to only twisting wires inside the arm itself?

Twisting the wires inside the arm alone would not help the problem. I am referring to twisting the arms so that the cables is the body turn 3 to 4 times like others describe.

Lukappaseidue · Feb 25, 2017

Mr Spock said:
Can someone pls share more detailed pics or a vid on how to remove the rear arms so that we can twist them till the wires are permutated 4 times?

I am with you.

BudWalker · Feb 25, 2017

Mr Spock said:
Twisting the wires inside the arm alone would not help the problem. I am referring to twisting the arms so that the cables is the body turn 3 to 4 times like others describe.

I'm not sure anyone has actually done this. I think @ScrappyMavic was going to then decided it wouldn't work. I think the only way to get the 4 or 5 twists internally is to take the top shell off.
I looked at these
(last half)

Mr Spock · Feb 25, 2017

BudWalker said:
I'm not sure anyone has actually done this. I think @ScrappyMavic was going to then decided it wouldn't work. I think the only way to get the 4 or 5 twists internally is to take the top shell off.
I looked at these

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(last half)

Thank you BudWalker. I see the top vid but yet is not exactly what i am after as it does not show how to do the leg removal and leg twisting without removing the top part of the MP and even that vid does not show details of removing the rear legs/arms. I found another vid in youtube of a guy removing them but it was too dark and the guy's head kept getting i the pic. Apologies all for going off topic.

flyNfrank · Feb 25, 2017

Mr Spock I also edited my last post.

Egika · Feb 25, 2017

pitchmagic said:
Ok, did a test run and get the same warning and the same numbers from Mag.Z.Back. Im taking out the screwdriver. Can someone confirm that i can twist the rear arm clockwise if I remove the torx by the end of the arm?

Highest p2p is 257;

Direction doesn't matter at all.
The Idea of twisted cables is, that EMC emitted by a pair (or triplet in this case) of wires will just cancel itself out if the orientation of the wires changes all the time instead of lying in the same order all the way.

flyNfrank · Feb 25, 2017

This might be good news for some. I opened it up and this is what I got straight from the factory. So we now at least know all Mav's built past the last of Nov. are ok.

However, I'm curious if anyone thinks the wires inside each arm should be twisted, straight, or doesn't matter?

Egika · Feb 25, 2017

Twisted is always better. Just the effect is smaller the more distance there is to other sensitive components. The arm is pretty far away from everything. But having the wires twisted there as well definitely won't do any harm.

agilealtitude · Feb 25, 2017

So the question is, since all of our MPs are still under warranty, should we pursue an official support ticket and try to send the unit in for repair, or do we risk voiding any warranty and do the surgery ourselves?

Sent from my iPhone using MavicPilots

pitchmagic · Feb 25, 2017

Egika said:
Direction doesn't matter at all.
The Idea of twisted cables is, that EMC emitted by a pair (or triplet in this case) of wires will just cancel itself out if the orientation of the wires changes all the time instead of lying in the same order all the way.

Thanks, I have built FPV quads, planes and wings for years and supressing magnetic fields is highest priority when designing and build. I was basically after the easiest way to do this on the Mavic. Is the one torx at the rear leg the key? I guess I have to see for myself.

BudWalker · Feb 25, 2017

Mr Spock said:
Thank you BudWalker. I see the top vid but yet is not exactly what i am after as it does not show how to do the leg removal and leg twisting without removing the top part of the MP and even that vid does not show details of removing the rear legs/arms. I found another vid in youtube of a guy removing them but it was too dark and the guy's head kept getting i the pic. Apologies all for going off topic.

According to this it's not possible to twist the wire bundle without removing the top. Once the top is off remove these two screws

and the motor arm assembly comes off. Twist the assembly 5 or 6 times and re-install.