I have a fried servo. The servo wasn’t moving like the others. I thought maybe it was an issue with the commands I was sending. I felt the servo and it was so hot I couldn’t touch it.
I let everything rest and it would cool down. Fired it back up but the motor would always lag. The motor didn’t feel loose like the others. I took the servo apart and the motor seems to turn free. The gears seem to turn free.
I started it back up again with the covers off on the servo. The board on the back would get super hot. I looked closer and the wires had melted through and were touching each other on the backside of the board. I might be able to take the wires out and solder it back together but I’m still not sure why this is happening.
Good news is the software seems to be sending the commands correctly! One can always get another servo!
Hitec will replace the servo. You will need to send it to me or directy to hitec. Take care to watch that you’re not putting a too much load on a servo for too long. It can cause servos to self destruct. It could also just be a bum servo though.
Thanks for the info. I purchased another servo today at a local hobby shop so I could keep working on my project. I’ll look into returning this one.
I’m going to be watching the servos more closely now! I think I read on the forum somewhere that you should keep them moving.
Would be nice to hook up a sensor to the ssc32 to tell me the electrical draw. That might have caught this one. I can do that with my Create and it works nice for indicating if I’m putting excessive strain on the motors. I have a threshold programmed to shut down the robot automatically if that happens.
That’s it! I read that in another place on the forum! Course I read it AFTER I had this problem. Oh well.
I’m back in operation. Thankfully I had five other Femur servos to look at for examples. I fired up the servos. I think they come up at 1500 by default. Then I adjusted it to be even with the rest.
There was one downside to all this. I had to cut all the twist ties and unravel the wiring so I could pull out the old servo and put in the new one. Everything was wired and tucked so perfectly in my Ready to Walk from Lnyxmotion before! Not anymore! Guess I should pick up some twist ties next and see if I can’t make it look a litter nicer like the other ones.
I went through one battery and everything seemed fine. Did have to tighten down some of the screws on the servos but everything felt (heat wise) ok.
Was seventeen minutes into my next test (running slowly) and the left rear Femur was hot. Right front Femur screw had also loosened up. I’m thinking I could really use some sensors to monitor the Femur servos while I figure this out. If anyone has a heat sensor solution that I can plug into the analog or digital inputs please post.
I’m curious how long anyone runs their robot before shutting down. 15 minutes, 30 minutes, an hour?
Does anyone swap batteries and keep running continuously. Just trying to get a feel for continual run time and if these run times are excessive for servo motors.
I have the front part of the battery held up by a pipe cleaner underneath the front of the Phoenix (the battery was mounted on top b4). I have the back part of the battery dragging on the carpet. Things seem to be better in this configuration but the left rear Femur is still a little warm.
These are casual observations that may or may not have anything to do with the heat problem. If it’s weight of the battery (and I’ve read that that can be a problem) then I can determine ways to deal with it. Will still need to do runs of 20 minutes or more to see if this really makes a difference or not. Just sharing obs.
Most people working with these bots will have them powered up for only a few minutes at a time. If you’re testing code then it’s powered up only in between code edits. If you’re showing off the robot to friends then 2 or 3 minutes is all most people need to be sufficiently impressed. Oddly enough the bots servos appear to be most happy when moving. It’s the holding position under load for several minutes that can cause the most trouble.
I’ve never worked with servos before so this is good feedback. I think I’ll program a timer to have it shutdown every couple of minutes to let things cool off. I still want to hook sensors up to the the servos to detect heat.
I agree, when moving it seems to stay the coolest. Some gaits generate more heat than others.
I do have a second ssc32 with servos attached that I use for some of my testing.
If one could identify overloaded servos (hot) that are used during desired gaits or actions, could they be replaced with more robust ones? Would a servo like HS-5955TG result in longer run times (20 minutes or more) with less of a risk of meltdown? Could they be combined with the existing HS-645MG servos? Would they just be a waste of money if put into a Phoenix? Other servo options?
If I were going to spend that kind of money I would opt for the 5990 with its heat sink case and the auto-thermal shut down protection. Because it’s a digital servo the code may have to be modified as the pulse range they accept is narrower than a standard servo.
That’s actually quite ironic, because if you notice some peoples homegrown IK engines, they have a ‘waiting’ mode where they just sit there and cycle through their legs, raising them up and down. It’d be interesting to see the current usage during this process.
Noodle93, I don’t think the cycling of the legs in hexapods were intended for that. I believe they are intended for clearing out the tips of the legs to make sure that it’s not snagged on something…
Over time, the leg tips, however precise the calculation is, will not land correctly as it is calculated, due to the resolution and precision errors in each servo, as well as the tolerancing of the mechanical build and brackets…
The tips of the legs then will land and move to locations that are not quite where you want it to be. Clearing out the legs and going idle (holding) instead of letting it hold without clearing out the legs would THEN be saving more energy, since it’s not snagged on something and the only thing it’s holding is the weight of the bot…
