Servo spasms while connected to LCD or USB - Why?

[ticedoff8]

Sounds stupid, but I don't have any other way to describe it.

While sitting on the bench while hooked up to the LCD or the PC (via the USB port), all the servos on the heli will randomly spasm at random intervals.
These are not small "jittery" movements - these "spasm" are near instantiations jumps from center to full lock and back to center.

I have 3 SK-540 (red), ver 3.40 (but, it has been happening on every previous version of SK software) and they all do it.

It is not constant.
The heli might sit for 2 or 3 min without a twitch or spasm.
Sometimes, it might be 10 or 15 seconds between spasms.
It might happen on 1 servo. It might be groups of servos.
But, at some point, every servo will move.

I used to think it was related to updating the gyro after a change.
But, even if I am not touching anything, they will still do it.

It got real annoying recently while I was leveling the swash on a Trex 700.
The 3 swash servos would spasm and the swash leveler tool would pop off the top and clatter to the table.
It was startling, funny, then after the 3rd time, annoying.

And, I use 3mm hex head screws to hold the servo arms. I had a Allen driver on the screw when the servo spasmed and thought I stripped the servo gear.

I figure this is "normal" because it is happening on all 3 of my SK-540 and every version of firmware for the last 2 years.

A) Has anyone else had this problem?
B) Is it fixed in 4.0X?

[Inkslinginmofo77]

Never heard of that one. U might try a different computer to eliminate it being a software or computer connection issue. If it still does it then u know it's from your gyro or wiring. EM fields could do this. But I'd start with loading sk software on other computer and check that. I'd personally do the 4.0 upgrade and see if that works because the 4.0 update is so smooth but ur field LCD won't work until Skookum releases the compatibility update in the next week or so

Also while u r bench testing it and connected to computer make sure it's on playback mode and not vibe. Disconnect and reconnect after a few glitches and look at your logs. U can see your voltage and see if u see any irregular activity. Are u using a power bus or just direct connection?

[ticedoff8]

You don't have an SK-540 do you?
"Vibe" and "Payback" are an SK-720 thing - no logging in 540.
I suppose I could send a log to Skookum and ask them to read it for me, but it really isn't worth the effort.
The "power buss" was used mainly on the SK-720 to reduce the vibrations associated with the wiring harness from the servos. The SK-540 have better gyros and don't have that problem and don't use the power-bus

I learned a log time ago not to jump into an upgrades for SK gyros - once in, you cannot easily go back no matter how bad it gets.

LCD support in a week or so? It has been 4 weeks of "LCD support by the end of the week" - so, I stopped asking.

Since this has been happening since 3.10, I suspect it has little to do with the SW.
I'll wait a while longer for the 4.0X.

Please re-read the post:
I have 3 SK-540 and they have been installed over the last 3 years on 5 different heli.
I've used Castle Creations BEC Pro 20, Scott Gray Reactor X2 and HVX regulators with 2S & 3S LiPos.
They all did it.

EM fields? Really?
No nuclear testing going on in my neighborhood (that I know of) or the flying field. The current fleet is 1 12S electric and 2 nitros. I wouldn't think there is too much EM on a nitro.

In the past 3 years, I've had the SK PC software installed on at least 6 different windows systems - they all did it.

[Inkslinginmofo77]

Okay sounds like a hardware issue. I would upgrade your firmware and see if that fixes it . 4.0 is a fantastic update. And if at that point it still does it then it's a hardware issue and needs to be sent in for repair

[pitounet]

Funny, after having installed the 4.0 on one of my 540, I had the re setup it. Guess what I noticed........ Small servo spasms. So it is not a hardware issue, you are not the only one and the v4.0 won't fix it. However since it is only during setup, I don't really care.


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[Inkslinginmofo77]

Must be software related then . I'd email Skookum if someone hasn't already and let them know

[pitounet]

I won't bother. It is just when plugged to a device and the spasms are tiny spams. It is not even annoying.


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[NHENRY]

I have this same issue since v4 on both of my 7SK20 and my SK540 whilst connected to my tablet pc running windows 8.1. It happens once in a while lasting 10 seconds of so. Only a minor inconvenience though!

[ticedoff8]

It is minor - until the swash leveler tool gets launched off and lands on your radio - or in your coffee (tea?) cup.
Or, you have the misfortune of having the allen wrench in tightening the servo arm when it spasms.
Like mine.
I guess that's the added "flavor" of using a Skookum. It has eccentricities with which we learn to deal.

But, I honestly worry about the affect this "spasm" might have on the throttle channel when an ESC hooked up.
I have a 600E with the CC ESC setup for "multi-rotor" mode - so I can use the SK's "bail out mode". Multi-rotor mode means instant throttle response.
Could a spasm cause the ESC to spin up?
I normally disconnect two motor wires when I am working on the 600E.
I bet a lot of people don't.

[pitounet]

Lol, I don't believe it. It seems that each time you talk about a problem I have it. Since my HELI doesn't fly the same since I put the v4 firmware and since I prefer the way if was flying before, I brought my PC in the field to try to setup it a way I like. I plugged and unplugged the module several times once it started to spool up on me after I plugged the USB port. It the blades didn't do a full turn, just a quarter of a turn. But since it is a 700, It was frightening. Now I unplug the esc before changing the parameters. I think I should have always done that to begin with.
My setup is 2x spektrum dam satellites, cc ice 2 120 hv.

[Inkslinginmofo77]

Honestly when I did 4.0 upgrade I had to re setup everything a retune it from scratch. It's a pain but worth it because the firmware is really smooth. Use the default settings in the setup wizards and adjust them from there.

[pitounet]

For the moment I still have mixed feelings about this version. The initial cyclic response was very slow compared to my previous settings, I had to bump cyclic acceleration to 45. I also have the impression that the cyclic feels less connected than before. Almost floaty in hover.


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[Inkslinginmofo77]

Give it a chance. A lot of specific and unnecessary settings were consolidated. For this u would have used hiller gain. But it's now part of over all gain. So if u don't want the floaty feel use higher hiller decay for a more locked in feeling. But if u want faster response u can up your bell gain as it makes your cyclic respond faster. feeling and less floaty. Your cyclic accel will allow your cyclic to move faster but your bell gain will allow u your cyclic to respond quicker to your stick commands.