IMU will not calibrate.

[Stevex]

Hi all, my P3A has sat in it's box for the last 18 months for various reasons.
After having a stiff word with myself I decided to fire it up and see how things went.
I've kept the batteries charged to approx 75% every couple of months and last night fully charged them all.
After starting the RC and drone it warmed up and all indications appeared ok and the drone was in GPS mode.
I tried to start the motors but a warning came up which said something like accelerator sensor out of limits, carry out IMU cal.
I carried out a compass cal first with no problems, but then noticed the drone was in P-Atti mode although I had 10 satellites.
I then attempted to carry out an IMU cal; the first stopped at 22% with 'unknown error'.
Further attempts with the same 'unknown error' only got as far as 2%.
Can anyone advice me on the way ahead please?

btw my software is App 3.1.30 v 1.11.20. I don't connect to the internet so the dji app thinks it's on the latest software. The drone flew perfectly on it and I don't intend doing an update.
Also noticed my Acceleration (g) values are x .01 y -.02 z -1.42; moving the drone about, the values do change but return to those stated. I've tried percussional adjustment with no success. Should the z value also be approx 0?

 

[Stevex]

Hmm, 90 views and not one offer of advice.
After Googling it appears a common fault amongst crashed Phantoms, but mine hasn't been crashed.
I decided to remove the IMU / accelerometer from the drone and took it apart but there don't appear to be any moving parts in there so not sure how so many owners get it working again by hard tapping.
I've found a used accelerometer on ebay, seems the only cheap option of repair I've found so far.

 

[Stevex]

90 views and no comments, I guess no one else has had this problem then.
Found a used IMU/Accel on ebay, seems the only cheap repair option atm.
I removed and stripped the IMU/ Accelerometer but there are no moving parts visible.

 

[3putts]

Sorry you did't get help, there are many brilliant drone minds on this forum. Unfortunately, I am not one of them.

 

[Deleted member 62848]

Here's a old post with good tip from @KachemakDiver ,,seems probably over time the imu becomes stuck but does involve getting inside,,,,hope this can help

 

[Stevex]

I have tried this, including removing the IMU and opening it up, this is what it looks like inside, photo attached. The middle part looks like a chip but I guess is the accelerometer. It's had a lot of 'tapping' but I'll give it another go.

Edit: Just had the IMU out again and gave it a good tapping on all sides. The z value has actually gone from -1.42 to -1.41, but apart from using a hammer I think I'm out of options, what ever is stuck is STUCK fast.

Edit 2: Final option, put on a vice and tapped with a hammer and pin punch, no change. Replacement required.

 

[shuggins]

Stevex, lets us know how it goes when you get your replacement part. I like how you had a "stiff word with myself". I had a word with myself for never flying my beloved P3S. I loved that thing for years and years. I pulled it out after reading this thread. Charged it all up and it somehow is fine.

I hope you get your P3A back fully functional once your part arrives. P3A is still a great drone.

 

[brigerdrones]

I have tried this, including removing the IMU and opening it up, this is what it looks like inside, photo attached. The middle part looks like a chip but I guess is the accelerometer. It's had a lot of 'tapping' but I'll give it another go.

Edit: Just had the IMU out again and gave it a good tapping on all sides. The z value has actually gone from -1.42 to -1.41, but apart from using a hammer I think I'm out of options, what ever is stuck is STUCK fast.

Edit 2: Final option, put on a vice and tapped with a hammer and pin punch, no change. Replacement required.

I laughed at second edit

 

[cheddarman]

An IMU sensor is a combination of an accelerometer and a gyroscope sensor, usually solid state. It is used to detect movements and measure the intensity of movements in terms of acceleration and rotational speeds. It is hard to see how tapping the IMU can have any effect on these things other than to possibly damage their fragile construction?

 

[Stevex]

An IMU sensor is a combination of an accelerometer and a gyroscope sensor, usually solid state. It is used to detect movements and measure the intensity of movements in terms of acceleration and rotational speeds. It is hard to see how tapping the IMU can have any effect on these things other than to possibly damage their fragile construction?

I thought the same, but there are a shed load of owners out there for whom the tapping fix worked. I believe there are moving parts in the IMU that sense the change in acceleration and g, they're obviously very small.

Anyhow, I fitted a used IMU, sourced from ebay for £30. Just fitted it and it sailed through the IMU cal. Now ready to fly.
FYI, all Phantom 3 models have the same IMU fitted, I seem to have been lucky to find a stand alone one as most people are selling them still fitted to the main board, the cheapest one of those was £60.

 

[cheddarman]

Anyhow, I fitted a used IMU, sourced from ebay for £30. Just fitted it and it sailed through the IMU cal. Now ready to fly.
FYI, all Phantom 3 models have the same IMU fitted, I seem to have been lucky to find a stand alone one as most people are selling them still fitted to the main board, the cheapest one of those was £60.

Good news! I'm not sure what sort of accelerometers the DJI drones use but I will find out. Probably Piezoelectric but possibly mechanical or MEMS.

 

[Stevex]

MEMS rings a bell.

 

[cheddarman]

It's basically a variable capacitance device rather than the Piezoelectric where a crystal is compressed causing it to generate an electrical current.