Did I fry my servo?

Hi there!
I got a new servo a few days back (RC Servo, Futaba FP-S148). I first tested it out with the Sweep sketch on Arduino, powering it with the Arduino 5v and GND pins only. It was working, just fine.

Today I was trying to use it in my robot and I tried powering it with 2 LiPo batteries (Samsung ICR16850 2200mAh, from an old laptop battery) connected in series, giving 8.32v. As soon as I connected my servo, it started rotating randomly, I had not connected it to my Arduino yet. I quickly took it out.

Next, I used a L7805 to get 5.13v regulated supply out of my batteries that I used earlier. When I connected my batteries to the servo, and the servo to the Arduino, uploaded the sketch, the servo started behaving rather strangely, it first did a complete turn and then stopped. Only a humming sound came from the servo. Strange thing is, whenever I connect one of my Multimeter leads to the power cables, the servo immediately turned in the opposite direction only as long as only lead was in contact with either the positive or negative wire. Otherwise, the servo just gives a humming sound.

I stripped down the servo and checked the motor. It is working fine. Moreover now the servo doesn't even makes the humming sound. It just sits there, no movement, no sound. I even replaced the gears from another servo I had lying around, they fit perfectly into place, but still nothing happened.

Have I fried my servo? Or is it some other issue?

I can't really tell without smellavision. :grin:

But seriously that servo is rated 4.8 to 6 volts and 8.2 volts probably did zap the electronics inside, sorry.

Maybe you didn't connect the ground side of your battery or regulator to the ground side of the arduino.

Southpark:
Maybe you didn't connect the ground side of your battery or regulator to the ground side of the arduino.

I did... That also didn't work.

outsider:
I can't really tell without smellavision. :grin:

But seriously that servo is rated 4.8 to 6 volts and 8.2 volts probably did zap the electronics inside, sorry.

That's something I don't wanna hear... Is there any way to repair it? Or atleast anyway to confirm it?

Buy another servo. Do exactly the same thing. If it also stops working then you know it is more likely your actions that killed the first one and not a random failure.

MorganS:
Buy another servo. Do exactly the same thing.

Dude that's not an option... the purpose of this thread was to find some way to make the servo work, If I were able to buy a new servo, I would have replaced it by now.

Depending on what exactly is fried, it is probably not repairable. Those little things don't have any space for a fuse or other protection device.

Even if you could identify the dead component on the circuit board and there were no other components damaged as a result of this one going kablooey, could you even work out the component value to be able to order another one? You would need the complete circuit diagram for the servo to give you that detail.

You may not be able to remember it but there used to be a profession called "TV repair man". The way those guys worked if they got a TV they'd never seen before was to call up the manufacturer and get a copy of the circuit. The manufacturers used to provide that because having their sets repaired "out in the field" was one way of upholding their reputation. If a TV brand became known as unrepairable, nobody would buy it. These days, that's not part of the manufacturer's reputation. The repair person could not replace any component without having the circuit diagram.

Even earlier than that, radios used to have the circuit pasted inside the back cover. Anyone could open it and see that it had a 6YG valve and order that valve as a replacement, even if the valve itself was exploded into little tiny pieces.

You will have applied too large a voltage to the controller chip on the servo circuit board, and its fried.
The rest of the servo is robust enough, but not the controller. Over-voltage damage on a chip is always
immediate and fatal - basically the case for all electronic devices really. Some 6V devices will tolerate
8V, others won’t, you were unlucky.