Melzi 5V supply drain current?

Hi all,

I, like many before me, am trying to connect my Raspberry Pi to my RepRap (pro Huxley).
I'm using the melzi V2 electronics supplied there with and was wondering whether there was any point on that board where I could draw 5V at 500mA without intefering with the RepRap operation?

Any information would be appreciated.

Thanks,

RomeoPapacy