Suggestions on motor/esc Testing???

[stj5353]

Hi, Today I took my Hex out to test some autopilot features. On a few occasions in the air, motor 3 cut out very briefly, around 250-300ms. It caused the entire copter to loose orientation, as you would imagine and then luckily it recovered. I was able to land w/o incident, but it was frightening.

My question is how best to troubleshoot. I'm not certain the problem is with the ESC. It could be channel 3 on my DJI, it could be the ESC or it could be the motor. Does anyone have suggestions that may help narrow down the problem area? I hate to just replace the ESC if the problem may be the controller logic or maybe connection internal or from the WKM.

Also, it wasn't consistent. I could fly for a few minutes and it would be fine. The cut-out was very brief and not seeming to be easily repeatable on command. Manual mode *may* have fixed it, since I didn't see it happen on manual, but also I didn't fly very high/long on manual because I wasn't sure if it was a ticking timebomb... I noticed it happen on GPS or ATTI modes, not that I think that matters. Unless the problem is with the WKM, which I'm not certain I know how best to point the finger yet.


Thanks for any insight!

-steve

 

[Motopreserve]

Take the props off and test in on the bench. Some hard fast movement of the throttle stick is what I would test first (for sync issues). You'll notice it on hard acceleration changes.

Make sure that all the wiring is solid. If you have a PDB, make sure there are no cold solder joints, and that all bullet connectors are right and secure.

If all that checks out - you should probably strap the hex down with props and put it through it's paces to see of you can recreate the issue.


Good luck.

 

[stj5353]

Thanks for the suggestions. I did check the linkage and connectors. I use the 2.5mm bullets on both the supply and motor side. Those are all very snug and I wiggled them all to check for any play. It's not the PDB, that's solid. I like your idea of strapping it to the bench. I think I will try that. But say I do recreate the issue, I'm not sure I would be able to tell you if the motor was bad or ESC or computer. Are there any ways to test these motors with tools like a multimeter? Or similar question with the ESC's? I'm handy with electrical work, but not sure a method to actually test them.

I'll strap it down monday and hook it up to my charger power supply and see what I can see. I had better be able to at least reproduce this issue. It was very scary seeing it wobble out in the air like that. I really want to be able to get to the bottom of it!

 

[Motopreserve]

There are some tests for motors (dont recall - but measuring between all the wires 2 at a time). Not sure it would really tell you everything you need to know.

If it happened after some time in the air it would seem like vibe or heat related. 2.5mm is pretty small for bullets. What are the specific motors/ESCs and batteries specs you're using?

 

[stj5353]

http://imgur.com/ldOkY7U
http://imgur.com/dArZVL5

These connectors don't seem small. They do not get hot after flight. Do you think I need larger ones? They seem to match the wire gauge well, 12ga supply. The motors are 390kv mated to 40A esc's.

Your thought about heat or vibe may be spot on. It took about a minute or two of flight to happen the first time. But then it flew ok for about another minute, then happened again.

 

[Motopreserve]

http://imgur.com/ldOkY7U
http://imgur.com/dArZVL5

These connectors don't seem small. They do not get hot after flight. Do you think I need larger ones? They seem to match the wire gauge well, 12ga supply. The motors are 390kv mated to 40A esc's.

Your thought about heat or vibe may be spot on. It took about a minute or two of flight to happen the first time. But then it flew ok for about another minute, then happened again.

It will be less about the size and more about the current being drawn through them. Most bullets used are 3.5mm (I'm surprised yours didn't come with them). Some use 4mm but more rarely. Do a search for the amp draw rating for the bullets you have, as well as the PDB. Then match it to the motor specs.

if it were me - after the issue happened once. I'd be on the ground. I would suggest sussing it out before it happens for a prolonged timeframe and you lose some hard work and $.

 

[jes1111]

Having those bullets hanging out there in free space is probably not a good plan. They'll be subjected to all the vibration going on in the area. My guess would be that a connector is hitting a resonance point - resistance suddenly goes high which heats it up at that point, restoring contact (and allowing it to cool again). Might be too fanciful an idea, but I'd change the layout anyway since the vibration will also be working away at the solder joints on the backs of the connectors (making a long-term failure likely). Plus I'd agree that the 2.5mm bullets are probably too small

 

[Bartman]

steve,
there isn't much airflow directly under the motors but those wires shouldn't be hanging free like that either. over time the vibrating action on unsupported wires cold-works them making them brittle and causing them to fail.

what motors and esc's are you using? manufacturer/model for each and is there anything special about the firmware on the ESC's?

 

[stj5353]

I've got 6x Dulasky MR Brushless Motor XM5015MR-6 + ZTW ESC 40

The ESCs should just be the latest simonk firmware according to my dealer. I have not bothered reprogramming them.

I'm going to bench test the heck out of this leg this afternoon. I have a replacement ESC handy that I'll fool around with and I can methodically try this channel on another motor to try to replicate. It's not really testing the devices so to speak, but it's as good as I can do to try to replicate the problem and tie the issue to any one part. Hopefully an ESC replacement will work. I really began to wonder if it may be associated with the mode the controller was in. It was most apparent in GPS mode, but I didn't fly it as long in ATTI or Manual, so it's possible it just didn't manifest as much in the other modes due to lack of flight time. But I sure did expect it to happen regardless. Just left an odd taste in my mouth.

As to the other suggestions, I'm thinking I'll turn the motors 90degrees and tie their cables under the mount with a zip tie. It seems that the common thread is to secure those. That's an easy enough done fix.

Oh, and I was mistaken, all of the bullets are 3.5mm.

Thanks!

 

[Motopreserve]

I figured they might actually be 3.5mm. Much better than having to replace them all!!!

swapping ESCs to another motor (and vice versus) will help you narrow the issue. Just check I to the replacement ESC if it wasn't bought in the same batch. Another member just determined that the newest ZTW do not have the same firmware as the slightly older batch. In fact new ones perhaps had no SimonK at all - despite being advertised to the contrary.

 

[Bartman]

i'd bet that the simonk firmware isn't very happy with those big pancake motors. do you know of other people successfully flying that combination?

 

[Motopreserve]

i'd bet that the simonk firmware isn't very happy with those big pancake motors. do you know of other people successfully flying that combination?

That's where the sync test would hopefully help. In my experience, SimonK and pancake motors definitely don't play nice...

 

[gtranquilla]

You should also test with the motors under load, i.e., with the props on and the MR solidly tied down to something heavy.... some issues reveal themselves only when the motors are under load.
BTW - you should provide all us with additional info as to the FC and firmware, RC transmitter used etc.
Troubleshooting is both science and an art.
And as we all know, focusing troubleshooting on the wrong area leads to a lot of wasted times and often no real ID of the source of the problem.
Unless I know exactly where to start based on previous experience, I like to start by focusing on the peripheral/perimeter items, props motors, escs and work my way in towards the FC and RC system.......
IMHO - FCs get so much blame for peripheral as well as misconfigured RC radio systems.

Hi, Today I took my Hex out to test some autopilot features. On a few occasions in the air, motor 3 cut out very briefly, around 250-300ms. It caused the entire copter to loose orientation, as you would imagine and then luckily it recovered. I was able to land w/o incident, but it was frightening.

My question is how best to troubleshoot. I'm not certain the problem is with the ESC. It could be channel 3 on my DJI, it could be the ESC or it could be the motor. Does anyone have suggestions that may help narrow down the problem area? I hate to just replace the ESC if the problem may be the controller logic or maybe connection internal or from the WKM.

Also, it wasn't consistent. I could fly for a few minutes and it would be fine. The cut-out was very brief and not seeming to be easily repeatable on command. Manual mode *may* have fixed it, since I didn't see it happen on manual, but also I didn't fly very high/long on manual because I wasn't sure if it was a ticking timebomb... I noticed it happen on GPS or ATTI modes, not that I think that matters. Unless the problem is with the WKM, which I'm not certain I know how best to point the finger yet.


Thanks for any insight!

-steve