Is there a way to test a suspected dead GPS\Compass?

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DLien

Member
Hi Guys,

How much abuse can the GPS/Compass sensor take and still function? Last week I had a NASCAR style crash from about 80 feet up caused by an unintended shift into crash (manual) mode. A mistake I will not make again. I had the GoPro hard mounted to top plate at the time. The 550 suffered multiple fractures of the arm for motor #5, broke both upper and lower plates at the at the attachment point, screwed up the landing gear nicely and of course a broken prop on that arm as well. The GoPro is alive and well, thank you very much!

Other items of interest, the impact was enough knock the IMU free of that super sticky mounting tape. I mount in the center of the bottom plate. I also mount for the GPS with that same tape. The GPS was mounted on the top plate where arm #5 attaches to the frame. There was enough force to dislodge the GPS/Compass sensor from the round disk at the top of the rod holding it up. There is no visible damage to either of these parts.

I have rebuilt the 550 and have kept up with the recent software upgrades. The trouble is that I can’t get the compass to calibrate or the GPS to give me less than 3 red blinks, in any mode or length of time waiting. I have no issue getting into the compass calibration mode. I get both the blue and the green LED signals but it always ends with flashing red lights (calibration errors). Before the crash (and software changes, which I don’t think is a factor) I could get no red lights (more than 7 satellites) and home locked in, in about 35 seconds.

At this point in time I suspect that the GPS/Compass is dead and needs to be replaced. Is there anything that I can do to test my theory and prove that there isn’t some other problem that needs to fixed?

I’d really appreciate any thoughts or opinions that the group here might have.
 

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Dewster

Member
The only way to cheaply test it (quickly) is to purchase another GPS/Compass. You should examine the connecting wire closely and the plug for broken contacts from the crash. My Hexa had a real, real, bad drop from the sky. Luckily the entire mount broke off, but it still hit the ground with some force. There are some scuff marks on the disc top, but I connected everything on my spare F450 frame and everything works like new. I did see that the insulation on one of the WKM wires was cut. I used electrical tape to cover it, but will replace the wire for my next build.

I don't know if the NAZA upgrade or if you can obtain just the GPS compass mount from a DJI dealer. I think I read somewhere that the compass was $35 dollars (I'm not sure...). Just make sure all of your connections are tight; no broken wires etc.
 

T

Tahoe Ed

Active Member
It sounds like you need a new GPS/Compass module. $169 for a replacement. You could send it back to your dealer to see if they can trouble shoot it before you replace it. I did the same thing, lawn dart from about 50ft up GPS first. GPS toast.
 

D

DLien

Member
Hi Guys, just a quick update.

I tried the compass calibration routine again (I was bored and really want to go fly) and it worked! Solid white light at the end!

Sensing a change in fortune, I took the 550 outside to see if the GPS would perform any better. No change on the GPS front. I tried for a bit more than 25 minutes and had there had three red flashes the whole time.

I’ll be talking to the dealer in the morning. Thanks again.
 

W

wdelarme

New Member
I had a similar issue with a crash and my gps. I took it apart and the ant itself had cracks in it (The metal looking area) I tried soldering runs across the cracks no luck had to buy a new one. I'm not sure how the ant is constructed inside if they have runs inside the ant or not....Not fixable as the ant is epoxied on the circuit board. I learned from this and made sure I cut the carbon fiber rod short on the new one. I had to make sure the GPS/Comp was below something else on the quad. Now a dome and all 4 props are higher than the gps and will take the crash. Not the gps
 


D

DLien

Member
I am still a bit of NOOB myself but here’s what I would do.

On the compass calibration, make sure that you can get into manual mode. When you are switching the mode control, end in manual mode, not Attitude or GPS. Works every time for me.

The other problem, holding an altitude, I am less certain about. Is your GPS connected? I’d also double check the vertical gain setting that you are using. I’d bet that it too low.
 

F

fvg007

Member
Thanks DLien. I will try that later...for vertical gain..I try 100% all the way up to 250% already.

I will try disable the Lipo protection feature ( just to see if this makes any difference )

Activate a throttle hold at 50% flat to test the hovering ( this is just to make sure I have throttle set to 50% to test if it can hold the height )

Will try to do a video to show ...thank you for everyone help...
 


F

fvg007

Member
Just come back from test flight and it works perfectly now!

What I have done:

1. Turn off Lipo protection under assistant.

2. Compass calibration.

Now ...I need to turn on the Lipo protection again and see if it makes any different! Thanks DLien for your help!

Anyone can tell me how often we need to do compass calibration ?
 

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fvg007

Member
Just did another flight..My conclusion:

1. Need to calibrate compass everytime after connect to assistant.

2. I notice after calibration ( when the system works - after engage motor ( intelligent mode ) it will cut motor if I dont increase power within 3sec )

But before, it will just keep running !

Is this normal ?
 

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