This is a discussion re the bad Accel, Gyro and Baro values that we're seeing with ArduCopter-3.1.  The increase in the SPI bus speed from 500khz to 8Mhz has exposed a hardware problem on some boards.  That hardware problem is that the 3.3V regulator has been blown so all sensors are running at 5V instead of the intended 3.3V.


How have these regulators been burnt out?

  • Attaching a radio receiver or MinimOSD to the APM while the APM is only powered through the USB (see video below)

  • Some clone boards seem to come from the factory with blown regulators.  3DR boards might also come with blown regulators although they do a specific check of the regulator as part of the regular QA process.
  • It is not (as far as we know) actually caused by the AC3.1 software itself, it just exposes the problem.  You could prove this to yourself by checking the 3.3V regulator (see video above) before and after the upgrade.


How can we fix the regulator?

Option #1:  If it's a new board (so that it's less likely you burned it out yourself) you could report the problem to the retailer that sold you the board and ask for an replacement.  If it's 3DR it's called an "RMA".

Option #2: if you're handy with a soldering iron you can replace the regulator yourself.  On the APM2.5.2 (and higher) boards it's not that difficult.  On the APM2.5 it's far more difficult.

For APM2.5.2 : TPS79133DBVR

For APM 2.5: MIC5219-3.3YML TR

How can I stop it from happening again?

Do not connect any devices such as a radio receiver, MinimOSD, GPS, etc while the APM is powered especially while powered only through the USB cable.

Attaching a 100uF capacitor across any of the APM's radio input's 5V and GND pins will stop the regulator from being blown by plugging in a receiver.  video here!

There are very few reports of regulators being blown twice and no reports of it ever failing in flight.


Below are some graphs of the types of values that we are seeing on these boards.

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All of what Detlef says is true but we have seen some 3DR boards affected as well of course despite the check at the factory.  Bruce's board and one more on the dev team and one more from a friend of someone on the dev team.

I have Bruce's board now but it's nearly completely broken.  The compass has completely failed and it doesn't even run AC3.0.1 properly anymore.  I'm not sure if it was the shipping it to me here in Japan that finally killed it or whether it was being run at 5V for a long time that did it but it's certainly not flyable anymore.

I see, 

So are we talking about bad boeard? bad regulators ? 

or maybe bad 3DR batch ?

I am only asking because I have my APM for nearly a month and it has flied only 5-6 times!!

I will check my APM on monday, 

If i do have a burned regulator it is possible to ask for a refund ?

The FC was bought from an official retailer in Germany.

Oh I should have mentioned I was using an external compass Randy. Out of the couple months I had it, I flew about 4 3000mah packs each weekend.

Aha!  so it's just the little trace has been cut, ok cool.  It's still pretty messed up though, the HUD moves like crazy even back on AC3.0.1.  Anyway, it's still been good to have it for testing.

Whether you can get a refund or not is really up to the retailer and 3DR...I have no idea!

Surebs sounds like she's going down hill. She did pretty good on Ac3.0.1 but did have a twitch now and then.

Hi all. I had this problem, and yes even going back to stable software doesn't help. It still says "Bad Gyro Health" and the crazy HUD. Luckily I found a guy in South Africa (where I am from) who has managed to source the replacement parts and fitted it for me. I am happy to say the board is as good as new :) :) :) Thank you all for helping identify the problem. The chaps name is "Wessie' and you can get hold of him on for a quote on repairing your board.

today I went 3.01 to 3.1 rc8 and I have the "bad gyro" problem , my 3.3v regulator is burn , my board is a rctimer ,  regulator is a tps 73133 , on the 3d robotics board it's a mic 5219 ,

 tps is a 100ma regulator , mic is a 500ma regulaltor ,  tps has à supply input -..3v to 6v , the mic has a supply voltage +2.v to 12v

this is may be the reason for all the problems

I think you forgot the zener diode D4 on the 5V supply that cuts everything above ~6V and blows the fuse. Probably not fast enough to safe all circuits but an indicator of serious over voltage.

Also the 500mA for the MIC is peak! On ~5.xV the MIC can only handle 150-200mA continuous without blowing steam out of the lid :)

I had the same problem as most, tested my voltage and it was ~5v instead of 3.3v. Ordered the part from digijey and replaced it and all works fine now. No issues and an easy fix.

I have order this model : , 500ma continuous in sot 23-5  package

it would be wise to put an alarm on the 3.3v , what do you think ?


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