SK720BE Motor Glitch

[dschmid4]

Skookum experts - I'm stumped. I've been trying to debug a glitchy motor issue in my 550E so I started a thread in that forum. Finally narrowed the problem down to my new SK720BE. Please take a look at this thread & video and let me know what you think.

https://www.helifreak.com/showthread.php?t=602286

[georgi UK]

=] hi, sounds like you are having a bit of a nightmare? the esc beeps are correct and it sounds like the SK initializes the servo's and you get the swash pitch-pump "all clear" conformation? (which it won't if there is an error state) I can see a red flash on the frames, is this coming from the recording device reflection or the SK?

the things to look for, does the SK give a solid green? has the throttle channel been reversed in the handset? does throttle hold have a minus value setting, even if you don't use the internal SK gov you must complete that setup wizard to calibrate the throttle settings. I will add more, if I think of anything else!

this is a recent unresolved current issue, yours could be related? both are BE 720's, they sound similar.....

https://www.helifreak.com/showthread.php?t=601681

[dschmid4]

Thanks for the reply.
* yes, the ESC arms properly and gives all the correct indications.
* yes, the SK720 initializes fine, pitch pumps, and led is solid green
* red flash on frames is from my camera.
* I did go through the throttle setup wizard (twice), and the throttle behavior seems to work fine as the motor spools up well with stick movement etc.
* This glitch happens with or without throttle hold engaged

[Luvmyhelis]

Originally Posted by dschmid4

Thanks for the reply.
* yes, the ESC arms properly and gives all the correct indications.
* yes, the SK720 initializes fine, pitch pumps, and led is solid green
* red flash on frames is from my camera.
* I did go through the throttle setup wizard (twice), and the throttle behavior seems to work fine as the motor spools up well with stick movement etc.
* This glitch happens with or without throttle hold engaged

This is the same issue others of us have had. But only using Castle esc's.

[georgi UK]

=] check the inputs from Rx in the software, is this a solid zero with closed throttle? like no throttle trim active in the handset? the odd bit for me is the esc signal isn't being controlled by the SK, ie it can't randomly spool the motor?

but, you are seeing this in different config's? it seems the SK hasn't seen your fail-safe settings, this should be done in the Utility tab, if this persists we need to involve SK.

[dschmid4]

Wizard says to set idle position with Throttle Hold enabled. Therefore, my software indicates a solid "0" when throttle hold is enabled, and "10" when disabled. Once gain, however, the glitch occurs in both throttle hold positions.

The fail safe seems to work OK.

[Luvmyhelis]

As just reported in the other thread. I had this same issue today with both my helis at the field. Both in TH after I set them down from test flights. Sorry for any misleading statements I made earlier. I couldn't get the problem to show on the bench after setting them up. But man did it give a couple nasty grunts outside as I was getting ready to remove the canopy's.

[FNFAL]

If one were to attach an analog servo to the throttle output of the SK (as in nitro use), would one see any servo twitching? Then how about a digital servo? Would there be a difference? Is there a refresh rate issue? Too high?

[dschmid4]

Originally Posted by FNFAL

If one were to attach an analog servo to the throttle output of the SK (as in nitro use), would one see any servo twitching? Then how about a digital servo? Would there be a difference? Is there a refresh rate issue? Too high?

Nice thought - I tried it tonight with a digital servo as I don't have any analogs. Take a look. I patched 2 different servo glitches (from about 10 min of recording) - the first is a quicky; the second is a sustained disturbance.
[ame]http://youtu.be/wNo8S_cnVzs[/ame]

[FNFAL]

Send that video to SK...tell them to explain this... ha! A pretty simple system arranged with no extra external input...yet the dithering...good work.

[Xrayted]

Originally Posted by FNFAL

Send that video to SK...tell them to explain this... ha! A pretty simple system arranged with no extra external input...yet the dithering...good work.

Yes, that rules out any particular ESC brands!

[SpeedTape]

Originally Posted by Xrayted

Yes, that rules out any particular ESC brands!

But, at least in this one case, it doesn't rule out the transmitter. Maybe post a log? Or better yet, email one directly to Skookum?

[dschmid4]

I'm emailing back and forth with Art at Skookum. Sent him setup file and a few logs. He asked a few good questions:
1 - Is it periodic (same time between glitches). Answer: no
2 - Does it happen when you move the heli around? Answer: yes, I captured a log file while moving the SK720 around slightly, and a glitch occurred.

I'm going to borrow an oscilloscope to visualize and dimension further. I'll keep you all posted on progress with Skookum. Luckily I'm doing this build while it's still cold out....

[dschmid4]

Originally Posted by Humming_Bird

But, at least in this one case, it doesn't rule out the transmitter. Maybe post a log? Or better yet, email one directly to Skookum?

I think if it where the TX, then I'd see this when using other FBL units or just a receiver. After all of my IS/IS-NOT's, I think I can say with certainty that this is an SK720 problem.

[omerco]

Originally Posted by dschmid4

Nice thought - I tried it tonight with a digital servo as I don't have any analogs. Take a look. I patched 2 different servo glitches (from about 10 min of recording) - the first is a quicky; the second is a sustained disturbance.
http://youtu.be/wNo8S_cnVzs

Only one problem with this video - Satellite to close to Tx. that is a known source for such things. need to be at least 30cm preferably more.

Want to try again maybe? if you have it at normal distances then you have a case.

[Skookum]

Hi Guys,

I have replicated this issue and know the source. About 1 in 8000 pulses from the throttle and IO-B channels (at random intervals), has an incorrect pulse width. It seems to be caused by an interaction with another function in the system.

Thank you dschmid4 for being observant enough to find this. The glitch occurs in single-pulses, so it is not a safety or performance issue (I have recorded *hours* of this stuff on a logic analyzer today). We'll fix this before the next firmware update, due out in a couple of months.

Best Regards
Art

[TBur]

dschmid4.. Nice! Great to see a quick and easy test and then verified by Art. Woohoo

[dschmid4]

Thank you Art and the Skookum team. Bravo - this is the kind of support which will make me buy Skookum again. Ah....um....that is, of course, if the firmware upgrade resolves this .

Just kidding, I'm sure it will. Thanks again!

[dschmid4]

Anyone heard anything about our promised firmware update?

Dan

[Luvmyhelis]

Originally Posted by dschmid4

Anyone heard anything about our promised firmware update?

Dan

It is being field tested as we speak by some very talented guys. Shouldn't be long now at all. As a side note, one of my Yge esc's on my Gob 700 is doing this now also. Kinda wakes me up while carrying a 700 back from the pad after a run and having the motor kick.