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IMU warmup at start now takes ages :(
2219 23 2016-4-21
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Bhujang
Second Officer
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So after all the latest updates for the p3p and the RC I decided to make a clean start and did a RC re-callibration, Compasss callibration and an IMU re-callibration. But now it takes ages for the IMU to warm up and initialise its getting warm here now with summer just around the corner so cant get the p3p cold enough to do an IMU recallibration below 10'C anywhere.
Any suggestions? Could I put it in an airtight bag in the chest freezer ;) ha ha or can that cause damage?

2016-4-21
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Drone Man
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Yeah,
You need to cool that thing down and then do an IMU cal,
I put mine in the frig  (38*) for 45 minutes with the battery REMOVED
and then do the cal.
Been doing it like that  from the beginning, never a problem
and my IMU initializes in seconds.
2016-4-21
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Bhujang
Second Officer
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Yes thanks for that. I thought that was the key to get the whole drone down in temp. Will put it in a black bin bag(so no damp gets in) and in the chest freezer for 10 mins. Hope there are not sensitive parts that can damage due to freezing or that it weakens the plastics on the shell... My fridge is too small lol.
2016-4-22
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Bhujang
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Else I have to wait til winter!
2016-4-22
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Drone Man
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Bhujang Posted at 2016-4-22 05:24
Yes thanks for that. I thought that was the key to get the whole drone down in temp. Will put it in  ...

I dont put mine in the freezer and I would NOT put mine into the freezer.
I put it in the frig,
My Frig is 38*, the freezer is at or below 0*, too cold in my opinion.
2016-4-22
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Aardvark
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Sounds a bit extreme having to cool things to such an extent. If you were to put it in freezer even if bagged the problem would be when you took it out of the bag into the warm air loaded with moisture, it would then condense on any cold surface including  internal  components.
2016-4-22
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JtrJr-UAV Pilot
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Bhujang Posted at 2016-4-22 06:24
Yes thanks for that. I thought that was the key to get the whole drone down in temp. Will put it in  ...

Bh,

Put it in the fridge (not freezer) for 20 minutes. Remove the battery and the SD card first! Do the IMU call immediately after pulling from the fridge.

Jerry
2016-4-22
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Gary C
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Drone Man Posted at 2016-4-21 09:38
Yeah,
You need to cool that thing down and then do an IMU cal,
I put mine in the frig  (38*) for 45  ...

I place mine in a medium plastic storage bag that has a valve to suck the air out with a vacuum. These bags are heavy duty and are used to compress clothes for storage or a trip. Cost is $10 + -. Keep in fridge for 30-45 minutes, then do IMU as others have suggested. Start up time after a cold IMU is 10 seconds or less. Must do this though after every firmware update.
2016-4-22
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DJI-Ken
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Have you tried what the others have suggested?
If so, your IMU warmup should be much shorter now.
2016-4-22
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Drone Man
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Here in NM its so dry I don't worry about moisture,
besides refrigerated air is dehumidified already.
I pop mine in the frig for 45 minutes or so then quickly do a
IMU cal, never a problem.
2016-4-22
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phinchman
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So, one thing that's always intrigued me is that I've been reading for months and months now, about how people put their birds in fridge for a bit and then do a cold IMU calibration.  And in this thread, DJI-Ken "seems" to support these suggestions.  So, how come this isn't called-out in DJI manuals/documentation?  I'm not challenging this, but wondering who originated this idea and why it's not "officially" documented anywhere ...?
2016-4-22
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AG0N-Gary
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Bhujang Posted at 2016-4-22 06:24
Else I have to wait til winter!

No need really.  While I am a very strong proponent of cold IMU calibration, what matters is that you do it cooler than when you normally fly.  Get up before sunrise and park it outside for an hour.  Then, take the house-warm battery out and do an immediate IMU calibration, before it warms up any.  When it is done, it should warm up quite nicely during the warmer parts of the day when you fly.  If you plan on doing cold flying, calibrated it at a cooler temp.
2016-4-22
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Bhujang
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Ok thanks everyone for all the input. I will try the early morning still night time really approach as its still going down to 3'c here at the moment some nights.
2016-4-23
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david.p.mann
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phinchman Posted at 2016-4-22 12:21
So, one thing that's always intrigued me is that I've been reading for months and months now, about  ...

The "cold-calibration" technique - to eliminate IMU warming up delays - has been recommended/validated as a valid/preferred technique by several DJI-employee forum contributors (and many Phantom flyers, including myself) going back 7-8 months - search the Phantom 3 forum.  I stick my P3Pro and P4 in the refrigerator for 10-15 minutes and immediately perform an IMU calibration on a flat, stable, vibration-free surface, followed by a camera gimbal calibration. I was hoping the need for the cold-IMU calibration procedure would be eliminated with the introduction of the P4, but it's still necessary to eliminate "IMU warming up" delays, particularly when flying in hot weather.  Thank goodness this "cold-calibration" is not necessary when I calibrate the IMU of my Inspire 1 - it would never fit in my refrigerator!
2016-4-25
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quanthonytrang
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david.p.mann@ea Posted at 2016-4-26 14:43
The "cold-calibration" technique - to eliminate IMU warming up delays - has been recommended/valid ...

It actually goes back years and it occurs with the p2 range.
http://www.phantompilots.com/thr ... -calibration.22688/

Best bet is to do the calibration in the mornings when the ambient temps are cool. Don't fly the phantom for an hour or so and do the calibration the moment you connect to the Phantom. The longer you let the Phantom idle, the longer the calibration will take and the higher chance of failure.

I don't recommend the fridge method as calibrating means to reset everything back to a known standard/yard stick. If the phantom is too cool, then you may get errors in barometric readings etc.

Also note.. if you calibrate at sea level (warmer) and trek up to the mountain top (cooler), your phantom will take longer to warm up.
2016-4-25
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joencasa
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Mexico
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Is necessary calibrate the IMU after the new Update of the P3A ?
2016-4-25
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Drone Man
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joencasa Posted at 2016-4-26 13:42
Is necessary calibrate the IMU after the new Update of the P3A ?

I alway do a IMU, gimbal and compass cal after an update.
2016-4-26
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Andrii.Shybanov
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I will try to put my Phantom 3 professional into the fridge before calibrating an IMU. Thanks
2017-4-5
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Phantomski
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yes, do imu calib when it's cold.. if u put it in a fridge, put it in a bag, to avoid condensation....
2017-4-5
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sdevan45
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OK, I'm befuddled.  Can anyone explain the physics behind why a cold calibration makes the IMU warmup faster?  
2017-4-5
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RicardoGray
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sdevan45@cox.ne Posted at 2017-4-5 13:37
OK, I'm befuddled.  Can anyone explain the physics behind why a cold calibration makes the IMU warmup faster?

I think the main thing to take out of this, anyway the way I understand it, the phantom needs to warm up to whatever the temp was when it was calibrated. If you calibrate at a warm temp, it needs to warm up to that before it is good to go. The reason for the cooler IMU calibration is that if you do this lets say @ 40 degrees, and you are going to fly when temp outside is 70 degrees, it only has to warm up to the previous temp (40 degrees) it was calibrated at. So ,it will reach that temp much quicker then trying to warm up to your 70 degrees. All I know is that is does work. Hope you can make sense of what I said.
2017-4-6
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method007
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sdevan45@cox.ne Posted at 2017-4-5 13:37
OK, I'm befuddled.  Can anyone explain the physics behind why a cold calibration makes the IMU warmup faster?

Your confusion stems from the way OP posted his question.  Calibrating your IMU when it is cold will not make it warm up faster.

The OP is attempting to say that he can not complete an IMU calibration because the IMU warms up too fast before he can calibrate it.

If I'm wrong on this, please someone correct me.
2017-4-6
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Phantomski
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Right, it does not make it warm up faster, it makes the "ready" temperature target lower, as you performed the calibration in a colder state....
Now, I will have to look at it.. but.. can you run the imu calibration BEFORE it says ready?
Either way, like 2 post above - the key is, that the IMU calibration temperature is what becomes the target temp for operational state.... that's the key.
2017-4-6
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sdevan45
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method007 Posted at 2017-4-6 07:20
Your confusion stems from the way OP posted his question.  Calibrating your IMU when it is cold will not make it warm up faster.

The OP is attempting to say that he can not complete an IMU calibration because the IMU warms up too fast before he can calibrate it.

OK, that makes sense.  I'm glad the laws of physics haven't been overturned.
2017-4-6
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