Opening a Dynamixel

[Saketh]

Hi,

I have got 2 RX 28's and a USB2 Dynamixel last week. I was trying to program using "Dynamixel Manager" and then I connected the battery with the wrong polarity and the Capacitor inside the motor has burnt out.And also the LED has stopped working. I opened the RX 28 and tried to figure out a way but couldn't do anything.

Can anyone please tell me if it would be sufficient if i change the capacitor with a new one or should i buy a new motor?


Thanks in advance,

Saketh.

[limor]

Don't think there's harm in trying to replace the capacitor.
I'll forward your question to Robotis

[StuartL]

You've probably blown the regulator (the small transistor alike thing) and the electrolytic capacitor. If you're lucky everything else is ok.

[Robo1]

with the back of the servo turn the servo horn. does it turn. if yes then the motor should be ok. Then you're got nothing to loss by playing with the electronics. have a play with a multimeter, they should be able to tell you the capactions and the resisence this should give you an idea of where the fault is.

Bren

[billyzelsnack]

If you end up not getting to work I'm sure there are plenty of people willing to buy it off you in the hopes that they could fix it themselves.

[StuartL]

If you end up not getting to work I'm sure there are plenty of people willing to buy it off you in the hopes that they could fix it themselves.

We've got a toasted motor and at least one set of toasted gears. A toasted PCB would complete the set

[Saketh]

Tried changing the Capacitor alone , no luck .

How do i change the regulator, i.e which one etc ?

I was actually planning to start making a biped soon , using RX28's. I had a very BAD dream!

I Connected the wrong polarity to 10 Serial Bused RX28's and thus all of them blew simultaniously.

So , is there a way to prevent this from happening ( except for the obvious like colour code and be careful ). I.e can we have a fuse, zener etc to prevent reverse polarity ?

@Limor, thanks. Did you get a reply from Robotis ?

BTW just curious , whats the going rate for a blown/burn't RX 28 ?

Thanks everyone

[billyzelsnack]

If you end up not getting to work I'm sure there are plenty of people willing to buy it off you in the hopes that they could fix it themselves.

We've got a toasted motor and at least one set of toasted gears. A toasted PCB would complete the set

How in the world did you toast the motor?? Was it locked up for a long time and did it get too hot so it just kept eating more current? Why did the temp shutdown not activate? Seems like Robotis might be able to replace that guy.

[billyzelsnack]

BTW just curious , whats the going rate for a blown/burn't RX 28 ?

Unless you just don't want to deal with fixing them then I'd throw out the suggestion to ask for help by sending one to an electronics expert here on the forums. I think the deal could be something like.. If you can fix it.. Keep it. Just tell me what's broken on it so I can fix the others! If you do this, make sure and put a timeline on it.

For the case of just getting rid of them.. Geez. I dunno. 10 of those guys is $1800 so.. haha. I still dunno! haha. I guess I'd pay 25% as making 10 openservo boards in the worst case would be a huge PIA! Maybe start at the 25% price on ebay?

One other thing.. You sure the servos are broke and not your interface?

[Saketh]

I did not burn 10 of them! I just burn't 1 of them!

I was just scared that if i connect the wrong polarity to a series of motors , they might all blow.

So is there a way to prevent this from happening. Can i put a zener diode to the battery connector before connecting to the motors ? This way the motors never recieve the reverse polarity.

Or is there a better way of preventing reverse polarity?

[billyzelsnack]

I did not burn 10 of them! I just burn't 1 of them!

Phffeww! Good to hear that.

[StuartL]

So , is there a way to prevent this from happening ( except for the obvious like colour code and be careful ). I.e can we have a fuse, zener etc to prevent reverse polarity ?

You could put a conventional diode somewhere in the circuit between the regulator input and the connector but that would involve patching the PCB. In our case we've made up some power cables that are prewired the correct way round so we can't toast anything.

How in the world did you toast the motor?? Was it locked up for a long time and did it get too hot so it just kept eating more current? Why did the temp shutdown not activate? Seems like Robotis might be able to replace that guy.

I think Robotis may laugh at us

We were testing the new firmware for the servos and somehow managed to heat up the motor so fast that it didn't dissipate the heat to the temperature sensor. We're not sure what happened, we think that the motor stalled without moving and as such instantly went to stall current (about an amp) meaning about 12 Watts of heat had to go somewhere.

We could possibly juggle this with Robotis but I bought the kit when I was working in the US, it was over a year ago and I have 36 AX12s cos I bought two comprehensive kits. If I'd only bought one I think I'd be keener to try and get a replacement. Now I had a 'scratch' servo housing that's got one set of stripped gears, the PCB we're using for PSX controller prototyping and the dead motor.

If we could get the entire servo replaced I'd jump at the chance. In practice I can't see it happening.