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
I am in Baltimore, MD. The board is a Hextronic from Hobby King. This was my first attempt with the APM. I was using the KK2.0 board before with a lot of success.
This board never even made it in the air. I was just playing around with it in Mission Planner to get an understanding of how everything worked and one day.....BAD GYRO HEALTH. It had the lasted firmware from day 1. I was hoping replacing the regulator would fix it, but seems there is more going on. It just bugs the heck out of me knowing I wasted $80 although I may have been the cause of this. If that is the case, I would love to know what I did!
I have since purchased a NAZA M v2, and am very happy with it as a basic FC. I want to use the APM because of all the cool features etc.
HK sent me a bad board with a defective regulator. In my case the regulator fixed it but the board was defective since day one. Back then it showed up with the new 3.1 firmware betas and that's how this entire thread started. So I wouldn't assume that you necessarily killed that board.
Their Hextronic seems to be especially bad with quality and working boards.
Thanks for the comments everyone. Does anyone know where I can find a complete schematic showing all the traces? The protective layer on this board is so thick and sloppy, I can barely see the traces.
Also, should the board normally power up at all with the regulator removed, or is there a separate 5v leg from USB?
Anyway, why fix it, send it back to Hobby King, get your money back, and buy a genuine one.
I wish I could. I bought this thing over 5 months ago, and have known it was defective for quite some time. I also bought another one from ebay, and it was labeled Ardupilot. It looked to be much better quality, but the GPS did not work so I sent it back and am waiting the replacement. I am not having good luck!
Dave, if you still have 4.7V with the regulator removed and nothing external connected then that is a sign that another component is defect and linking the 5V to the 3.3V.
If you are lucky you find a bad solder blob on the board that connects two pins causing this issue. Worst case its the PCB somewhere in the multilayers - that would be the death sentence for the board.
To find that component its almost impossible. You would need a very accurate multimeter (3 digits behind the decimal point) and probe the 3.3V line around the board. In the area where you get the highest reading that is where approximately the defect component is located. In that area you can then start cutting 3.3V lines or start replacing components that you suspect. Its a try and error approach...
I figured 3.5V was pretty close but this is a board that won't run any firmware at all. I'm just troubleshooting to see if it might be salvageable and just came across this post. I may give this a try too.
http://diydrones.com/profiles/blogs/no-solder-method-for-defective-...
It's not a big deal if it's no good as it has just been sitting around anyway.
http://youtu.be/TWUr69GztxA
Messy but effective, and no damaged tracks
Hi,
Can someone put together information how-to-not-connect-things-to-apm to not blow reg? I follow this thread from beginning and more i read i'm more confused.... Is there any good way to connect apm to PC with battery or it is not relevant if i first connect the battery to PM and then PC or in reverse first to PC and then battery... I should only connect esc signal wire (i did it already) or should i connect all 3 wires? There are some minimum batt voltage?
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