voltage - Reducing 12V to 5V

DISCLAIMER: I know nothing of electrical engineering I just seen this as the best fit category for my question.

I have a solar panel that is being run to a controller switch (for lack of a better name) the controller switch then has a hookup for a battery and a hookup for output. I have the battery connected and its supplying 12V - 12.8V to the output.

I want to hook up a female USB end to the the output. But I know that a USB port should only provide around 5V.

Before I had the controller and battery I had the solar panel hooked directly up to the guts of an old cigarette lighter phone charger. It worked great. But when I tried to hook up that same little circuit board to the output of the controller it just arced and so I removed it.

Have no idea what I'm doing wrong here. I hooked a voltage meter to the output and sure enough, 12V. Hooked a LED light up to it and it lit up real bright. But whenever I hook up that little circuit it arcs and if I hook up the circuit board from the inside of a USB wall charger... Nothing, no power coming from the USB port (measured with voltage meter).

Answer

The simplest circuit will be using a voltage regulator like LM7805. These regulators are very common.

However, it can only supply a maximum current of 1A and you will also need a heatsink.

It is simple to build: connect the 12V wire at the left most terminal of the IC, while looking at the inscription and with the pins down. Connect the 5V output for USB port at the right most pin. Connect the ground of your 12V supply and of your USB to the middle pin or to the heatsink. You may also add two capacitors like:

From Fairchild datasheet.