Hexy curls up and dies (under powered?)


#1

I’ve completed a new Hexy build and thoroughly tested each servo and connection.
I’m using the Powerex batteries that were recommended and I’ve tried both the 4 and 5 cell configuration and both exhibit the same problem.
I’m using Pomoco 2.0 under Windows 8.1

So…if I connect 4 of the 6 legs, everything works fine (if a little spazzy and jerky)
I can continue to add servos one at a time and I can actually get to the point where they’re all connected and working, but within a few movement changes, all legs curl up in the air like a dead spider and it takes a reset to get anything running. On reset, it will go into an epileptic seizure and end up legs up again. If I disconnect all but four legs (well…13 servos…12+1 head) it’ll be fine. Anything more than this and it’s just a matter of time before it locks up.

It doesn’t matter which combination of servos or ports. I originally thought that it might have been a flaky servo taking things down, but no such luck. Surprisingly, 4 or 5 batteries doesn’t seem to affect the number of servos. (though with 5, the power wires actually start to melt together.

Any ideas?


#2

As additional info, I just received a 10A 5V power supply that I’ve now got connected. The issue still exists, but in a slightly different form.

With the 10A supply, the jittering has gone away. With 4 legs, the Hexy is responsive, smooth and rock solid.
If I add any additional servos, instead of curling up and dying, everything just twitches when I send commands, but nothing responds as it’s supposed to. I can remove the servos without a reset and when I get back down to 13 or less, it starts responding again.

The specific combination of servos doesn’t appear to matter.

Any thoughts?


#3

Between this and what we’ve been talking about in your support emails (its better to stick to one please), I’m going to go ahead and exchange your board for a new one. Reply to your support ticket and we can get a new one out to you right away.


#4

I just checked arcbotics.zendesk.com and there are no existing or open requests. Are you sure that you’ve got the right person? The only support email that I sent was regarding the power connectors on the board not matching the jacks provided. I didn’t hear back, so I just made new connectors and moved on.

This is an entirely different issue and I just assumed that since I didn’t see a response to the first one, there wasn’t any point in submitting a new ticket.

If your reply got caught in my spam filter, I apologize. But I certainly haven’t had any discussion with anyone yet.


#5

I see it, but if its stuck in spam, its probably best to file a new one. If you file a new one with help@arcbotics.com we can get you a replacement board. Just be sure to include your name/address/phone number.


#6

I was having the same sort of issue. Hexy couldn’t even perform a lot of the moves in pomoco without crumpling. I was using Energizer 2300mAh batteries because I couldn’t find better ones. I connected a 5V 5A power supply, and the problem went away. The servos had enough strength, and moved more fluidly. The problem with NiMH batteries is their continuous current output. It’s often not very good compared to NiCad or LiPo. They have good overall capacity, but not current output.

Not wanting to have a tethered robot, I decided to change to a LiPo battery pack. At the hobby store, I picked up a 7.4V, 1000mAh pack from some sort of drone. It can supply 10 amp continuously. I ordered a DC-DC converter to regulate the output to 5V.
aliexpress.com/item/5A-Lithi … 96219.html

It works beautifully! No more curling up like a dying spider. This is what I had in mind when I ordered this robot!

This battery pack weighs maybe a third of what four AAs weigh, so a larger capacity pack would be fine too, if you want longer run times.


#7

My Hexy is currently back home at Arcbotics getting looked over by the pros. I suspect that something more than a power issue is going on, so I wussed out and sent it in for a once-over.

That is a very cool idea though and one that I’ll look into when I get him back. I never even thought about using a dc-to-dc converter and I have LiPro packs all over the place. (D’oh!)