Does the nikon d3100 have a built in intervalomiter?

Does it have one or do i buy one if so is it the micro USB connection

Nope! You'll find them only in the high-end Nikons. I think the D5000 may have one.e-bay has some at great prices.

No, but it does have a wired remote, so you should be able to find a 3rd party intervalometer for it.
I use this one for my D90:
http://www.amazon.com/...001QSG4R8/
It doesn't specifically state D3100, but I'm sure the D3100 uses the same connector, so it should work. If you don't want to risk it, there are other 3rd party intervalometers that do state they work with the D3100 wired remote port.
At any rate, the wired remote would connect to the Accessory Terminal on your camera, not the micro USB port (the accessory terminal is above the USB port).
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