Tarot 680 Pro integrated PDB failure - major smoke!

[jmooreou]

I recently built a Tarot 680 Pro. I have built several multicopters, but this was to be my first APM setup. I completed a couple of test flights and I was sorting out some issues in my house, reading logs, etc when all of a sudden the top (PDB) plate started spewing flames and smoke.

There were no crashes or even hard landings prior to the fireworks.

I was using a 4S battery and I don't have any idea why the board failed, but I am pleased it happened while on the ground. I did some searches and I have found where others have experienced similar failures with the 680 Pro top plate (PDB).

I have had identical failures with the small PDB boards that I used in some 250 racers. I stopped using one particular HK board when two of them burned up in succession. It was the same exact type of failure - major flames/arching with a lot of smoke, and I never knew when one might decide to burn up.

Anyway, I plan to rebuild the 680 Pro but I am going to use one of these...

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=68699

and not use the PDB in the 680 Pro top plate. At least if this new PDB fails, I won't have to rebuild the entire kit!

This is just a head's up for others building/flying this model. I really like the integrated PDBs but I'm not going to risk another failure with this one.

 

[Motopreserve]

I had issues with a HK cheapie PDB as well, long ago. It crashed the MR and for me, that was the end of using their PDBs.

I'd make sure you do some research on that new one you plan to use. There are some extra components on there that could cause issues, and make sure you calculate your amp draw so that you have some headroom. Vulcan and a few other companies make decent, and simple PDBs of various ratings, for not much more than this one. They don't have the bells and whistles though.

Please keep us updated on how you make out. These little things can cause so much heartache - yet it's a component that is often overlooked and under-appreciated.

 

[violetwolf]

I generally avoid printed circuit boards altogether, preferring to make a harness or use solid copper to make a bus bar etc. The thickness of copper on most pcb's scares me.

Not that I'm right on this by any means. Just throwing out another idea.

 

[Motopreserve]

I generally avoid printed circuit boards altogether, preferring to make a harness or use solid copper to make a bus bar etc. The thickness of copper on most pcb's scares me.

Not that I'm right on this by any means. Just throwing out another idea.

In fact, I was told that the printed board in the 680Pro had issues. After having some problems with some ESCs, john over at AddictiveRC mentioned that a few clients of his recognized that the ESCs runs were varying in length, causing some FCs to not recognize the ESC when arming.

I never confirmed this personally - because I moved on the ESCs that had no issue with the integrated board - but it's something to keep an eye on.

 

[jdennings]

I've found that the challenge with integrated PDB's is ratings. You'll see things like 300Amp, 70 Amp, etc ... but without some sort of temperature indication, resistance, or testing conditions these numbers are close to meaningless. "Rated" 70A, what does it mean? That the board will go up in flames at 71A? That it will dissipate 10% of the corresponding power in heat? 50%? 90% Without specs on the traces in mils it's impossible to know. And some are actually not rated at all ...

That said I've used some, they sure are cleaner than wire harnesses especially for octos. But it's a matter of trust of the manufacturer and making sure one stays well under the "rating" ... For high power stuff wire harnesses feel safer.

 

[Motopreserve]

That's definitely a good point. Keeping track of what the integrated PDB can handle and playing it safe is probably the best bet.

But in fairness, I have to say that I've trusted manufacturers of external PDBs on their ratings without testing them too. Granted, I buy from reputable companies, so i feel their numbers should be solid (or at least my use will be well within the limits).

 

[jmooreou]

OK... Here is an update on my original post.

I rebuilt the 680 Pro using this PDB
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=68699

Note: I DO NOT RECOMMEND using this PDB with the 680 pro due to mounting and clearance issues, but with some modifications I was able to get it installed. I did like the fact that it had integrated APM connector as well as 12v BEC.

When I finally got everything back together (using the Dremel to address some of the clearance issues) and connected the battery for the first time there was a "pop" and the unmistakable smell that normally follows.

The 5V from the PDB to the APM controller was dead, but the 12V and the main connections to the ESCs seemed to be fine. I used the APM power connection on the battery lead instead of the one that was integrated on the PDB and soldiered on. Anyone who has built the 680 Pro knows what is involved in bolting the two halves together and I didn't want to tear it apart again unless absolutely necessary.

The initial pre-flight tests seemed to check out fine, except for the fact that I could't get GPS lock...

I did a brief hover test (about 2 foot AGL) in my front yard in Stabilize mode and all seemed fine.

I took it to an open field for the first flight test. Again, no GPS lock but I decided to just gently fly it in Stabilize mode to see how everything was working and sort out the GPS issue later. The craft actually was very stable and flew well... for about three minutes. All of a sudden it started spinning violently out of control and my RC inputs seemed to have no effect.

The hex goes out of control at 3:24

The frame was pretty much demolished. The motors/ESCs/gimbal (hopefully) seem to be OK. The GoPro has a nasty dent in one corner - not sure if it is damaged, but it was still recording this movie when I picked it up, so it may be just cosmetic damage.

I haven't taken the time to examine all the connections or the logs, assuming they are available from the APM.

I ordered another 680 Pro frame. I'm still trying to decide what to do about the power distribution. I am leaning towards just fabricating one out of copper - keeping it simple with a couple of BECs for the 12v and 5v. I have another APM to use in case this one is damaged. I think this combination will make a nice camera rig if I can get it all together and working and I really want to explore some of the autonomous flight capabilities of the APM.

Onward....

 

[Chalagi]

The Tarot 680MM Pro is one crappy designed hexa. Some of the screws are not long enough and after assembly the top and bottom plate will be warped. And the way you have to level your motors are just completely unbelievable. Those should have been predrilled with tapped screw inserts. Sorry but I can go on for hours about how that designed that Tarot. And mine also had a break in the filament of the pdb that caused me all kinds of trouble.

 

[Motopreserve]

Sorry to hear about the crash.

I think it's wise to create your own PDB at this point. The fact that you smelled some burning and heard the pop makes it likely that the damaged PDB could have given out in some way during your test flight. Perhaps power flaky to the ESCs?

Glad to hear you're getting back in the saddle with another build.

 

[Old Man]

IMO, integrating the PDB with the frame is not the way to go with any MR that will carry a payload of any significance, even a Go Pro .

 

[m_beeson]

Well, this is disturbing. I just built the 680 Pro. So far I really like it, but I'm not happy to hear that the PDB is likely to fry.

-Mike

 

[Old Man]

Buy one of the older 810 folding frames, and if you really, really, just gotta have a 680, chop off the arms a little. Eliminates the PDB frame plate. Another option is don't use the PDB arrangement and install a central PWB under everything. Tarot is not the only one that has experienced shorted/blown integrated frame electronics.

 

[violetwolf]

I love my 810. It's been in service for 3 years and still solid.

Personally I just don't like the idea of printed circuit boards for power distribution. Lots of amps an thin copper traces.. It gives me the willies. And lots of threads with tales like this. I generally make a harness.