Servo not reacting - nothing happening

Hello folks,

I have just connected a servo and neither of the testing programs are working (I tried sweep and knob)

Sweep: I copy-pasted the code and uploaded it to the board (Arduino v.14, Duemilanove Board), connected the orange wire to Digital Pin 9 as stated in the code, connected the board to USB and the servo power cables to 6V external DC. The servo gives one initial twitch as I plug in the adaptor, but besides that - nada. What am I doing wrong? Is there anything special about the library I have to do?

Thx4help, I´ve been stuck on this for days now.

did you connect the 6 volt ground to the arduino ground?

Amazing. That was the solution. Thank you so much!

(Could you please be so kind and explain to me why I have to connect those? It seems like I am missing some basics...Thx a lot bow)

a pin is high when it has 5 volts in reference to ground. since the grounds of both your circuits were isolated, when your pin went high, the servo saw no potential to its ground, so it did nothing essentially. when you connected the grounds, their potential became the same, and now when your pin went high, the servo now saw 5 volts to its ground, because its the same ground as the arduino. that may make no sense, i really suck at explaining things.

perhaps a read through this wikipedia article might also help. http://en.wikipedia.org/wiki/Voltage

Ah! Now I see why I don´t need that extra cable when not using external power for the motor (or using the power jack to drive both the board and the motor - the Vin pin is starting to make more sense;). I think I was not really aware of the difference of a servo and a relay-driven DC motor circuit.

Thanks a lot!