running motor with external power

hallo - we're having trouble running external power through the arduino...

we've switched the jumper to the right position, but we don't see the power light come on on the board, and the voltage in the 9V pin is only around 1.5V...



what kind of DC power are you giving it through the DC in Jack?


Hi going to jump in on this too and add a newbie question that I can't find an answer to.

I want to run of a 9v external power supply but before I go blowing the damn thing up can someone tell me which way round the ploarity should be - positive center ?

Sorry this is a really dumb question but hey gotta start somewhere!