if it is for charging a USB device it should not pull more than 500 ma. I made one of these devices a while ago and just soldered a 9V battery snap to the input side of the LM7805 and a usb connector on the output side and wrapped it all in a blob of electrical tape after bolting the LM7805 to a piece of metal. It worked. Since than more efficient designs have been released on to the internet such as the
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