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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Hi randy

My board also missing that capacitor, has no dataflash issue and 3,3v is OK,

3DR offer to replace the board, but i refuse because it will cost me around $50 to send it back.

Well I have just ordered the external compass/GPS module and will investigate when it arrives... in the mean time, I'll try and track down the specs of the regulator in the module so that we can discuss its capabilities.

Thanks to all!

I'm sure that the Apm, original 3DR, that had the 0V output and no dataflash error issue, happened when it was connected and powered only with usb cable, nothing else, I mean no other cable or wire was connected to the Apm.

The usb connection was with my ground station where a mini itx Intel mainboard was powered with a dc power supply.

Hope it works fine for you. I was regularly checking this page to see if any reply came from Craig. Nothing so far...

Hope he can see this question and make a comment. I would like to know for sure if what you think is going to work Lachy...

Hi,

the SPI bus speed from 500khz to 8Mhz for Arduplane ????

Best ;)

Any drop in replacements for APM 2.5 for the regulator?

Really don't want to scroll through all the pages.

Yeah I could get a exact part replacement, but I was wondering if there is an alternative part.

Fred,

     My guess is that they've increased the bus speed for plane as well.  It all uses the same underlying code to talk with the mpu6k.

I hope i am in the correct forum location to get an answer to a regulator question.

Well here goes i finely got a new regulator on the board it seams to be up and running i connected to the board via the usb and mission planner flight data page no longer displays bad gyro health and all looks normal when i pick up the quad and move it around the hud corresponds mission planner loaded 3.1 on the board i can get the motors to arm and spin but now i don't have GPS the little blue led dose not light but when i go into terminal screen and run test gps it shows a coordinate heading it did work the led worked before the reg went out so is there something in the new 3.1 firmware that turns it on or did it blow.

Thanks 

Hi Randy ,
Thank you very much for your fast response ;)
i use in this moment aduplane 2,76
the Code is affected by this ?(SPI bus speed from 500khz to 8Mhz)

Best ,

Dennis,

     No changes to the GPS lights in AC3.1.  I wouldn't trust that gps cli test very much though.  I've heard it produces garbled messages.  Do you not get a GPS lock anymore?  I think you should be able to check by looking at the HUD on the flight data screen of the mission planner.  If it says, "No GPS" then there's a serious problem.

Randy 

This has been frustrating to say the least first the quad was flying just fine an hour before upgrading the firmware to 3.1 and then not working at all i might just through in the towel on this one.

Dennis 

Dennis,

      Sorry for the troubles.  You may be able to downgrade back to AC3.0.1 (see Previous Firmwares" link in the mission planner's install firmware page).  With each version we require more and more CPU.  For the boards to keep up with what we're asking of them they've got to be in good health.

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