Thread: VSA/Controller Help!

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I'm using VSA with a Pololu Maestro Controller for my 3 axis skull.

I keep having the same problem where my servo's start acting all erratic. I'm not sure if this is a power supply problem or what? All servo's are well within their movement limits. Nothing binding. Any ideas?

Lindberg Skull, T Pro SG5010 Servo's (4), 7.2V 2000ma power supply.



Let me know what you guys think!! Need to figure this out ASAP! Thanks in advance.

Notice the strange movement at the end of the video.

Does it only do that when you're trying to move, or even if the command is for the skull to sit still? It looks a little like it could be a resetting problem, caused by voltage drop. I say this because toward the end, it looks like it makes quick, jerky motions (trying to do the proper move), but then slowly sags down, as though the power had been removed.

- Hook

It only happens when moving usually when I'm trying to move multiple servos at once or I'm making quick movements. That's why I'm thinking it's a power supply. I just noticed the supply I'm using says switching power supply. Any idea if this is the problem?

I am in now way electrically inclined. Thanks for the help!

That definitely sounds like a power or grounding problem. 'Switching' supply is good, but it may be that you're trying to draw more than 2000mA from it, and the supply may be shutting down, temporarily. Do you have a voltmeter? If so, try measuring the supply during this routine, and see if the +5V drops to zero during the seizures.

- Hook

I will check that out tomorrow. Is there anything in either VSA or the controller software that I could have screwed up somehow?

Another question, is the 7.2v too high of a voltage to power the servos? Should I be using 5 or 6v instead?

This is my first 3 axis as you might be able to tell. What do people normally use for their servo power supply?

Thanks again!

You know... I don't know why I didn't see that before, but yeah, that is kinda high. Most people use 5-6V. I'm not sure whether the servos would be okay with that, or not. Here's a thread discussing just that. Where did you get this supply? I don't think I've ever heard of 7.2V coming from anything other than a rechargeable battery. It's not meant to be a battery charger, is it?

If you've got a 5V supply around, definitely try that out first.

- Hook

I had a 5v 850ma supply that I just tried. Definitely moved slower (as expected). But no jerky erratic movements. Only problem is after a few test routines it seemed like the power just ran out and it slowly died. If I unplugged the supply and plugged it back in, it work work again for a bit.

I'm guessing I need a supply with more amps. Eventually I'll be operating 6 servos in the skull, any suggestions on power supplies to acquire for this project?

Thanks again Hook!

Man, you got gremlins! I dunno what's up with power in your place, but that's some weird stuff.

If you can get your hands on a computer power supply, use that. They've got loads of current. You just have to jumper two pins together, to turn them on. See this page. If you don't have one lying around already, pick up a 5V supply from All Electronics.

- Hook

I'd say stick with 6v max for the servos. I typically use 5v supplies that have pots on them that let me crank the voltage up to 6v. To be safe, especially if you are dealing with fast movements, provide at least 1Amp per servo.