servo "waving"?

Hexy Questions, Problems and Suggestions
#1

So I completely assembled my hexy without properly calibrating the servos and am in the process of going back through and centering them. (I don’t know why exactly, but while I was building it when I plugged them in to the board they’d whirr a little bit but didn’t actually center).

Anyways, right now I’ve got one, that when I set it to zero in PoMoCo (or any other value), it sorta waves back and forth a little bit and slowly dies down over a second or two, but doesn’t actually stop. Should I replace the servo?

#2

Is it a hip servo? If so, that’s normal. It will stop waving once the foot is on the round.

#3

no, it’s the upper leg piece. It’s the only one that’s doing it.

“set zero” should move everything so that the legs are all pointing out flat like a star, right? This one leg, no matter how I attach it, shoots down (or shoots up) and just waves back and forth. If I reattach it so that it’s pointing out, it still shoots down (or up) once I start sending it signals.

#4

(it’s attached to #14). I tried plugging it in to a couple of the other plugs and same behavior.

#5

I replaced the motor. It no longer does the weird waving thing. But it’s not behaving properly… maybe the batteries? Maybe some of the servos are loose?

Basically what’s happening is a couple things: for one, the “get up” command doesn’t work. It starts, and then hexy ends up in a weird position where all the legs are in weird directions, like he’s standing on the rim of a bowl with his body hanging down beneath his feet. The second thing is “dance” – it starts off fine but never begins to resemble a dance. after the first couple commands I can see the sliders in PoMoCo moving but the servos aren’t doing anything.

After trying out these, “zero” no longer returns the legs to the same position. several of the legs or feet are pointing in weird directions (like up).

Oh, another thing: it sometimes seems that I need to “kill all servos” twice before it goes quiet. I tap it and I can still hear the hum of one or two of the motors; tapping again stops it.

#6

oh, man, now it’s doing things even after I quit PoMoCo. Something’s wrong, but I have no idea what.

#7

Yeah, this is classic low/improper batteries. The weird legs in every direction thing is what some refer to as “spider curling”, because it looks like how a spider curls its legs in when it dies. The solution is to get batteries that are more charged, or if you aren’t already, use NiMH batteries. We have more information here:
github.com/ArcBotics/Hexy/wiki/Powering-Hexy

#8

So close! I ordered 2 packs of the Powerex 2700 mAh NiMH batteries & hooked 5 of them up to the servos. Power supply does seem to be the primary issue. It’ll now do most of the things in PoMoCo, mostly. I’ve gotten hexy to get up, dance a bit, and do several of the actions.

[redacted – turns out I did have 2 of the connections swapped, which explains some weird leg behavior]

But I’m still having some power issues even with those batteries, fully charged. I think. Sometimes “set zero” still doesn’t return all of the limbs to their original positions (but if I go through, leg-by-leg and resetting & then disabling the servos, it works).