Thread: VSA & SSC32 Servo Strange Behavior

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The other day, I converted one of our talking skelly heads from jaw movement only to 2 axis. The jaw was connected to our SSC32 board on channel 16. I connected the nod and rotate servos to channels 19 and 20. Channels 17 and 18 have other props on them. I created movement events in VSA for the 2 axis on channels 19 and 20 and adjusted the jaw movement for the servo connected to channel 16.

Now it gets weird! I'm watching the playback which goes for a minute or so without jaw movement and all is good. THEN, when the routine gets to the jaw movement commands, the rotate servo on channel 20 begins to respond to signals from the singing part of the routine. There are 5 other props (a total of 6) that sing this bit on their own VSA channel so I'm not able to determine just how the rotate servo is receiving commands from the singing part.

I tried disabling all of the servos except for the rotate on channel 20 and it still responded to jaw movement action. SO, in VSA I moved the routines from channels 19 & 20 to channels 17 & 18. After doing that, I still had a slight bit of jaw movement action on the rotate channel but I can live with it.

What I can't figure out is why I was getting what seemed to be a leaking signal in the first place, and then why changing the channels to put all of channels for that prop adjacent to each other would drastically reduce it?

That's definitely weird.

How are you powering your board and servos? if VS=VL jumper is set, make sure you have enough current so the board doesn't reset when all the servos start going.

Did you make a wiring harness? Maybe there's a short on the signal wires allowing signals from one channel to bleed over to the other?

Can you screenshot your device settings screen in VSA?

-DGM

I tried disabling all of the servos except for the rotate on channel 20 and it still responded to jaw movement action.

This tells me it's not electrical in nature. If you disabled the other channels in VSA, then the signals weren't there to short to or receive crosstalk from. Have you looked at the 'events' in VSA for the rotate servo during the time the problem happens? Maybe some of the jaw moves got accidentally copied over into the rotate track. Or WaveMotion Analysis was done on that channel by accident?

Just some thoughts,
- Hook

Are you using an actual serial cable or USB-serial adapter? I know that some people have had issues with the SSC-32 when using the adapters.

Are your servos wired directly to the SSC 32 or are they wired to a CAT5 ether-net cable or something similar? If one of the rotate servos are shorting out on ground they will pick up stray signals.

Originally Posted by Hooked_on_Scares

This tells me it's not electrical in nature. If you disabled the other channels in VSA, then the signals weren't there to short to or receive crosstalk from. Have you looked at the 'events' in VSA for the rotate servo during the time the problem happens? Maybe some of the jaw moves got accidentally copied over into the rotate track. Or WaveMotion Analysis was done on that channel by accident?

Just some thoughts,
- Hook

Ya, that was my first thought but there is nothing there but a long rotate event.

Originally Posted by Dr Morbius

Are your servos wired directly to the SSC 32 or are they wired to a CAT5 ether-net cable or something similar? If one of the rotate servos are shorting out on ground they will pick up stray signals.

Now that may be a possibility. The two new servos I added are wired through a cat5 cable. If the signal is bleeding through it isn't impacting the source. All of the other props behave normally. So, I'll do a continuity test on the new wires I made and see if I have any shorts. Thanks for the suggestion, I appreciate it very much.

Status update:

I never resolved the problem before moving on because my plan was to replace the wire to the servo that appeared to be leaking over. So, yesterday I added 3 servos to a prop making it a 3 axis. While setting up the VSA events for it I had all of the other servos disabled. When I enabled the prop that seemed to be leaking over, I got that "jaw movement effect" on two of the servos on my new 3axis.

Eh, ok. I figured I'd replace the wires in the "leaking" prop and everything would be great. Whoa, it's way worse! In fact if I enable all devices, everything just jitters.

I'm thinking now, that even though I have measured power on bank 2 of the SSC-32 board at 6vdc, I'm not getting enoug power. Right now I have a 4amp 6vdc power supply connected to the first VSA power connector with the jumper set to power both banks. I'm gonna try adding another 6vdc power supply, set the jumper for separate power and see if what that does.

You would think that a 4amp supply would be plenty, but maybe there's some kind of "noise" in the power when there is a large drain on it.

Originally Posted by buckaneerdude

Status update:

I never resolved the problem before moving on because my plan was to replace the wire to the servo that appeared to be leaking over. So, yesterday I added 3 servos to a prop making it a 3 axis. While setting up the VSA events for it I had all of the other servos disabled. When I enabled the prop that seemed to be leaking over, I got that "jaw movement effect" on two of the servos on my new 3axis.

Eh, ok. I figured I'd replace the wires in the "leaking" prop and everything would be great. Whoa, it's way worse! In fact if I enable all devices, everything just jitters.

I'm thinking now, that even though I have measured power on bank 2 of the SSC-32 board at 6vdc, I'm not getting enoug power. Right now I have a 4amp 6vdc power supply connected to the first VSA power connector with the jumper set to power both banks. I'm gonna try adding another 6vdc power supply, set the jumper for separate power and see if what that does.

You would think that a 4amp supply would be plenty, but maybe there's some kind of "noise" in the power when there is a large drain on it.

Sounds to me like the old floating ground issue. Make sure all ground connections (servo, SSC32 and power supply(s) ) are all tied to the same point. All power must be referenced to the same common ground connection. A floating or separate ground will cause signals to stray onto ground wires through the servos.

The second power supply fixed it. I went back for the umpteenth time to read the SSC32 user guide. It really doesn't say how many amps you need to power how many servos. All it really says is "VS of 6.0vdc 2.0amp wall pack for up to 8 servos." Somehow I hadn't seen that before. I guess I was reading the specs for battery packs. Things were going crazy when I went over 17 servos with just the one 4amp 6vdc power supply. Now that I understand better the first power supply at 4amps would handle 16 servos. I suppose that would explain why things went crazy with the new added servos.