Servo and USB vs Battery

Hi All,
When I plug in my servo to digital 9, positive to 5v and negative to GND on the bottom of the board and plug it in over USB the servo does not operate.
But when I plug it in over Battery (NOT THE VIN) it works fine.
Any Ideas?
I am using the Duemilanove.

I have the same problem with Arduino 2009, using a Servo from the German shop Conrad.de ( here's the link).
I try to to pilot a LED on the same port 9 using PWM and the port works fine.
I used both the Servo library example embedded in the Arduino 14 IDE (Sweep and with potentiometer analog reading) and the example
here (itp.nyu.edu) , but the servo doesn't move at all.
I used also serial communication to print the potentiometer reading, and everything work fine, apart the servo.
I have some doubts about the connection, but I'm pretty sure that

  • black goes to GND.
  • red goes to 5V.
  • yellow (the last, but not the least) must go by elimination to the Arduino pin.

Am I right?
BTW, I know that I have to test with the battery too to see if the Servo is dead or not, but I haven't battery at the moment ;).
I'm very interested in any tip, comments are welcome.

But I remember it working before over usb

Please,
Someone I need ideas.

I’m not an expert, but I want to help.

Did you used one of the Servo library? If yes, which one?

But I remember it working before over usb

Did you use the same motor before successfully wt. Arduino?

But when I plug it in over Battery (NOT THE VIN) it works fine.

Did you connect the motor directly to an external source (battery) and it worked? If yes, I’m interested how you connect it to the battery, my servo is not responding at all, I just try to connect an external 5V 1A charger, using

  • charger +5V <> to motor positive
  • charger GND <> to Arduino GND <> and motor GND
  • motor yellow <> to Arduino pin 9

I try to control directly the servo, without any Servo library.

Here's something else really wierd.
I can power the arduino over the battery but then i plug in my power adapter (wall plug) and that doesnt work!

Yet another observation:
When i use power over USB it works for a couple seconds then stops working

One Last Thing:
It is a vEx servo
if that means anything
a servo is a servo right?

I think the Vex may use non standard pulse timing. A google search should turn up the specs.

There's only one problem with all of this.
It worked perfectly a couple days before.
Maybe I need to buy a new arduino

can power the arduino over the battery but then i plug in my power adapter (wall plug) and that doesnt work!

If you run a test sketch that does not use servos, does the arduino work? Servos can draw more power than the USB or regulator on the board cabn provide.

Perhaps if you use a seperate power source for the servo all will be OK.

Yes, the arduino works fine over usb.

It seems that providing a seperate power source for the servos would solve the problem

It must have taken too much power before

I think the Vex may use non standard pulse timing. A google search should turn up the specs.

Good idea, I found a very useful infos for my motor here and an interesting hack to my servo ES-030 here to have endless rotation (sorry, it's in German).

How can test if my servo died?

Problem solved: after 1000 tests, I decide to open the servo and the wire contacts are completely fired (photo), then I try to fix and rewire everything (photo).
Luckily everything works fine, now I have my knob-controlled servo-spinning, directly from SouthPark :sunglasses:


Thanks to everybody, this post helped me to think more about my project.