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.
Replies
Thanks guys! From the various pictures I see around the net, it looks like the one I have will work and so will the power module. Getting better :-)
Cheers
Tim
The only cause that's been found is repeatedly plugging in the radio receiver while the APM is powered through the USB port. People find the issue when they upgrade the firmware because the newer firmware exposes the problem, not because it causes it.
Well looks like I may have been bitten by this as well... I checked my old APM 2.6 that was running the latest firmware as of Aug 2013 and it's 3.3v was fine on the I2C cable.
Then spent most of today upgrading to 3.1.2 and trying to get the damn thing to talk to Mission Planner. Terminal Window works perfect but Planner won't connect.
Total frustrated after hours of troubleshooting... checked my 3.3v on a "lark" and sure enough, its now 0v. Not impressed. Since it never worked from the second I flashed 3.1.2 I can only assume that 3.1.2 was the cause of the regulator blowing.
Everything was plugged in at the time of the flashing (GPS, Compass, Rx but not OSD or Radio) when powering via USB and the flash went fine. Just MP would never connect again except via terminal window. Done this millions of times with the old firmware and never an issue.
Going to order a couple of spares and see if that fixes my connection error. Will ensure battery power is on before connecting USB for this test.
Here is the start of my woes from the forum:
http://ardupilot.com/forum/viewtopic.php?f=12&t=6830
It's extremely unlikely to be the firmware that blew the regulator. Software causing a hardware fault is very very unlikely. Don't shoot the messenger!
Hi
This is the exact problem I have as per the discussion yesterday. It happened as soon as I updated the firmware on the 22nd of March
Without the compass plugged in all works, but as soon as I plug the compass into the I2C connector no more working!
How easy is it to replace the regulator in the Pixhawk, there does not seem to be any reference to that here. Is it the same as the 2.6?
I need to get this resolved having paid $500-00 for all the bits and postage I am pretty disappointed!
Many Thanks
If yours blew when you plugged in the external compass, you must have plugged it in backwards. Other than that, I haven't heard an incident where it the external compass causes any issues with the regulator.
Also I am not aware of the any regulator issues on Pixhawk boards so far...
If that's a Pixhawk and your HUD is spinning it could be this issue:
http://diydrones.com/group/arducopterusergroup/forum/topics/pixhawk...
Is this an APM?
Let's try and keep the chatter about the value of clones vs original 3dr apm boards to a minimum and instead focus on the technical questions and answers around the 3.3V regulator.
See? I miss out on ANOTHER dead APM board...
mnem
Re-Use is the highest form of Recycling.
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