Phantom 2 goes up on its own

[quaddamage]

I assembled a Phantom 2 out of parts I gathered. One of these parts was probably faulty.

The drone warms up properly, sees satellites, starts engines and goes up. It reacts properly to small corrections of position. It reacts to all the other RC controls as it should.

When I order it to go full forward, it goes forward as expected, but soon after it starts going upwards as well.
It fires upwards quite fast, sometimes it stops after 10 meter, sometimes after 30m.

Once it did the fast upward move while hovering, after correcting position to a wind blast (relatively fast but short increase in wind speed).

After such fast upward move, when I regain full control and bring it back where it was, the drone does not hold altitude for some time - it slowly descends.

I have my pick on what might be faulty, but I'm not completely sure - wanted to hear Your opinion as well.

EDIT: I did all the possible calibrations in Assistant app.

 

[J Dot]

Could be 4 possible things.

1) gps ( possibly plug loose/wobbly ) or bad contact.

2) compass ( out of calibration ) or loose/damaged wire.

3) Accelerometer ( out of whack )

4) Tx out of calibration!

Any of these can cause strange occurrences as you stated!

You said you are using the assistant app!

Do you have a laptop or Pc?

If so go to dji.com
And download the following:
1) RC Assistant
2) PC Assistant
3) Driver

( I don't use the app, the Pc seems more legit and thourough! )

Let's first do a full fresh calibration:

1) hook your Tx ( radio ) to Pc via mini USB cable.
( if you have an older remote, you'll need to remove the rear cover to locate mini USB port INSIDE, newer Tx is external. )
Ok
Run RC ASSISTANT,
Turn on Tx
Do a FULL calibration
( both sticks, both toggles, and dial wheel ( if avail? ))
This will calibrate your Tx back to factory default!
Ok Turn off Tx, unplug ( reassemble if needed ) close RC ASSISTANT!

Open PC ASSISTANT, hook phantom to Pc via USB cable, and turn on Tx and bird.

Now under basic tab, then RC, calibrate your Tx again ( both sticks, toggles, and dial wheel ( if avail ) this will calibrate your Tx to your bird, so they are in sync together!
While you are here, go to ADVANCED TAB, and do an ADVANCED IMU Calibration ( phantom perfectly level ALL directions and stationary ( no wobbling around ) then once this is done, turn off bird , unhook USB, and go outside, for a fresh compass calibration. ( take your time. There is no time limit here, just slow and steady, to get a nice calibration )

Now go back inside, hook bird to PC ASSISTANT,
Go to values page ( mod values )
Please post the following info for us.

Accelerometer mod value
Gyroscope mod value
And compass mod value

History:
IMU = Inertial Measurement Unit
This takes readings from :
ACCELEROMETER = and straight movement ( up-down, side-side, and forward-reverse movements ( straight line movements ))
GYROSCOPE = and spinning movements, like Yaw ( as a vinyl record spins )
COMPASS = your position in magnetic earth, depending on your areas declination, may not be true north, but rather magnetic north, usually within 10 degrees or so!

Ok
Now these readings are calculated, and averaged, creating a MOD VALUE,

From word MODDUS, meaning Absolute value.

So if any of these are off, you can get a bogus reading, and can confuse the IMU in the flight controller ( NAZA unit )

So we need these all on, then your bird should fly like new!

But also check for any faulty wiring ( damaged, or exposed, stuff like that ), loose connections, everything should be tight and snug, if connector wobbles around, this is not good! Either glue in place or replace all together!

Try this out and let us know!

J Dot



Ps: also let us know what mode you are in ( NAZA or phantom )
And may be stupid question, but you fly with BOTH TOGGLES UP? Correct?
Hope this helps! Take care, Fly Safe!

 

[quaddamage]

Thank you J Dot, that's a very extensive guide to calibration.
I fly in NAZA mode, was using mostly GPS Atti. while I was testing the drone, but I also I checked whether the other modes work (they do).

I was actually only interested in speculation about cause of the issue - I'm not willing to spend much more time on it.
I am preparing to sell my Ph2's - I moved to Ph3 when the prices dropped (prices of used ones) after Mavic came out.

1) gps ( possibly plug loose/wobbly ) or bad contact.

I don't think GPS has any part in computing altitude; why do you think it may be involved?
Note that the drone does keep XY coordinates as it should, even while moving upwards on its own.

2) compass ( out of calibration ) or loose/damaged wire.

I've never seen compass affecting altitude. Bad compass calibration usually results in the drone "dancing" in the air (doing constant corrections on rotation). It also causes the drone to do arcs instead of straight lines when going forward (or in any direction).
Still, I don't know enough to be able to say that I'm sure compass is not the cause.

3) Accelerometer ( out of whack )

Yes, that's totally possible. I didn't considered that. Although it would have to be a very specific failure - after all it usually works fine, only when the drone is at large tilt the issue kicks in. And it only affects altitude.

4) Tx out of calibration!

I have another Ph2 which works fine, and I'm using them both with the same radio. The Assistant app shows readings from the sticks in correct range.

My pick for the offending component was different - I blame barometer. Maybe it is not soldered properly, or there is some dust inside which blocks the MEMS part when tilted.
Unfortunately the PC Assistant does not show readings from it. What do you think?

(MEMS is Micro Electro-Mechanical System).