Is there a sensor ON the board or what???

I am new to Arduino, but not electronics. I have a very strange thing happening though that I can not explain. I have a sketch that should just toggle an LED on/off when I press a momentary button. If I wire it through a breadboard, it works as expected. However, if I connect the LED directly from any pin that I set the output to to ground, if I move my hand near the board at any angle close to the ICSP headers, within like 4 inches, the LED will light up (and pulsing, not just a solid signal). Why is this happening?

I also have a servo that will not work with any sketch, and only slightly jerks when I first apply power. I was thinking it was just my servo but is there any way that these two things could be related?

Sorry if this is something noobish.

Post your code, using code tags.

Any Arduino input that is left “floating” (not connected to ground or Vcc through a wire or a resistor) can pick up stray electrostatic fields. If you happen to be reading such an input while waving your hand nearby, you will probably see changes in the readings.

jremington:
Post your code, using code tags.

Any Arduino input that is left "floating" (not connected to ground or Vcc through a wire or a resistor) can pick up stray electrostatic fields. If you happen to be reading such an input while waving your hand nearby, you will probably see changes in the readings.

Ah, that has to be it. I had the input wire not connected and was near where I was waving my hand. Good to know though, that thing really is sensitive! Seems like one could almost use an exposed open wire as a short range proximity sensor! :astonished:

Well, there is a capacitive sensor library. That makes use of the fact that an Arduino input is very high impedance.
http://playground.arduino.cc/Main/CapacitiveSensor

The servo motor could require 500mA when it starts rotating. Use a seperate power supply for that.
If you would use the USB to power the Arduino, and the Arduino 5V to power the servo motor, you end up with what you describe. Do you also use a cheap bad USB cable ?

I am using 4 AA batteries to power the servo. Shouldn't that be enough?

4 AA batteries to the Arduino power jack ?
And the 5V pin of the Arduino to the servo motor ?
No, that is not enough.

I write down 5 possible problems (but I can write down many more): The batteries might be too weak, the start current of a servo could be larger than 500mA; The wires from the battery could be too thin; Perhaps you use a breadboard with bad contacts; The Arduino doesn't get enough voltage; The Arduino output pin can't supply enough current for the servo motor.

I know some examples on the Arduino site use the 5V pin to power a servo motor. But both in theory and for real, it will fail in most cases.

I have the batteries going straight to power and ground on the servo, and the PWM of the servo in pin 9 on the arduino. They are brand new batteries, a brand new breadboard and battery holder. Unfortunately I don't own a multimeter at the moment so I can't check the current I'm getting from them, nor does the Parallax site say the required current.

If you want help, post your code, using code tags and post a wiring diagram of the entire setup.

The AA batteries might be too weak. A RC battery pack would be better.
And the Arduino GND is connected to the Servo ground ?

Yes the grounds are both connected together. I don't really think pictures at necessary, it is just a simple circuit and I am literally using the basic servo example sketch that comes with the IDE.
I am thinking you're right about the current. Just thought it would be more simple than this to get a single servo working, like you said, all the guides don't even mention using a separate power source.
What kind of rechargeable battery would you recommend?

For example an RC battery pack.
A photo can be helpful, we all make mistakes.
I think you need a multimeter, check everything and you should find the problem quick.