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
Hi . I have been reading the post regarding the 3.3v issue ..What I want to know is ..
a) What is causing it to blow (short out) ? Software or too much load?
b) If it is replaced will it blow again ?
c) What model of Reg should we use .. a higher rated one?
As I only see posting for Micxxx no numbers.
Now I am too scared to fly as I have thousands of $$ hanging under my copter ..plus the cost of the machine its self!
Cheers R
Hi guys, I would like to thank everyone for all the work done. What a dedicated group! This will be my first post, I've spent several months reading, ordering parts and building. I am building a Hex using the RCtimer 2.5.2 board. I have followed all the instructions, Especially Jabram's posts. ESC's are not powering the board a separate 5v reg does that. 3DR 413mhz radio for telemetry, connects to Mission Planner just fine. Black foam on the barometer. Turnigy ESC's I flashed with SimonK. It hovers good. GPS locks in, But, that is about as far as I have got, wind, weather hasn't allowed any other testing and tuning. The hud was very stable.
Today, I upgraded the firmware to 3.1 and as soon as it booted, Mission planner shows and speaks "Bad Gyro Health" and some other message that sounds like: "prettier ends not healthy" can't really understand what the first word is.
Am I one of the unfortunates with a blown 3.3. Regulator? I measured it and it's 4.7v or so. And, if so, what is the recommended replacement? If I replace it, will the board work or does the excess voltage blow anything else? I can do the repair as long as I get the proper part and nothing else is blown. I read about this being a problem with the bus speed increase. I haven't tried it but if I go back to the previous firmware is it possible it might work since the bus will run slower? Any thoughts or replies would be greatly appreciated.
Hi guys,
A client of mine just sent me back a damaged jDrones' APM board, problem description: "BAD GYRO message on HUD"
It means the problem is not only regarding to 3DR boards, right?
Hi,
I have an APM2.5 (3DR) that intermittently suffers from the 'drunken HUD'. I observe this periodically if I leave it connected to MP while it is sitting on my desk. Needless to say it is useless in this state... I have measured the 3.3v output and it is a consistent 3.402V - 3.408V This is not too far off but still outside the spec for the regulator. Would you still suspect this as the cause?
Alex O asked:
-Does this affect certain batch of APM2.5s or it could happen to anyone?
I asked Craig (3dr) and he tells me that they specifically check this when the boards leave the factory. All humans make mistakes but as far as I know, there is no know batch of APMs that left the factory with this problem.
-If so, what can we DO to prevent this from happening?
I've personally never had this problem so I think if you handle your boards carefully you don't need to worry. In particular don't hitch up your ESCs backwards with the JP1 jumper in place. There may be other ways to cause this that I don't know about though.
-And lastly, if it does happen, what are our options?
We're trying to make AC3.1 automatically downgrade the SPI bus speed so if you have the problem you'll get a warning on the HUD and you'll need to disable one of the ARMING_CHECKs but the copter should still fly as well as it did with AC3.0.1. That downgrading code is in -rc7 but it's not working so it needs to be revisited.
Of course, the incorrect voltage is possibly already causing small glitches even with AC3.0.1 so the best solution is a new board or to replace the regulator. Detlef's managed that, I personally don't actually know where the regulator is on the board nor exactly where to get a replacement regulator...but I'm hopeful we those details will emerge!
I've made a little video of how someone could test the regulator on an APM2.6 without pulling it from it's case. Of course as mentioned earlier in this thread there are a number of places it can be tested, this is just one of them.
Bruce, Detlef or anyone else suffering from the problems on this thread,
I was wondering if you could give this modified version of -rc6 a try? It's -rc6 (or maybe closer to -rc7) and includes some extra logging of the MPU6k spi bus errors in the dataflash's PM message in a new "INSErr" column.
Like -rc5 & -rc6, this version runs the MPU6k at 8MHz but will reduce it to 500kHz after it detects 4 errors. On a broken board this should happen almost immediately. If you connect with the mission planner you will probably see:
1. "Bad Gyro" appears on the HUD and you can never make it go away (sorry!)
2. "PreArm: INS not healthy" appears when you try to arm
Despite these problems the MPU6k should work as well as it did in AC3.0.1 and you can force it to arm by going to the CONFIG/TUNING > Standard Params screen and set ARMING_CHECK to "Skip INS" and press the "Write Params" button. If the "Skip INS" option is not there go to the Full Parameter List and set it to "-17". That may seem like a weird number but that's because ARMING_CHECK is now an 8 digit bitmap so when the highest bit is set it becomes negative when viewed as a signed byte.
By the way, there's probably no need to actually fly it (although I think it will fly fine) a bench test should be fine.
RC5 is looking good on my APM 2.6. My first attempt at Autotune ended in a crash - Looks like 3 meters is not a good starting altitude. 10 - 15 worked much better. Definitely need a nice big open area. Altitude hold and loiter are great! Stab mode is sweet also!
Thanks guys!
is this noticeable and happening as well in rc4? What behavior is noticeable in flight? I have rc4 loaded and on occasion I get a weird jump on one motor as if the bearing jammed for a 10th of second or so. I checked the motors and swapped them and teh ESCs around, but it still happens off and on so it cant be a faulty motor or ESC. It might not happens at all for a whole flight so its weird.
Well i need to step back and redo my measurements. But definitely something wrong. Stay tuned....
-
26
-
27
-
28
-
29
-
30
of 30 Next