Hi , this is my first instructable so go easy on me :)

So i am going to show you how to power nearly anything off a USB port

This is for the USB competition

USB runs at 5v. The max current you can draw is 500ma. Therefore the max load is 5v x 0.5A=2.5. Watts. (W=VxI) If you try and draw more than 500mA, you may overload the port which will cause it to break

UPDATED PICTURES :)

Just a WARNING to look what your circuit needs if it needs a higher Voltage/current this can break your ports make sure you have got the correct details of the circuit WARNING

Step 1: How Many Volts ?

So to power something off a USB port it has to be under 5 volts as thats how much a USB port gives out so you can check this by ;
Looking at what battery is being used
4 x aaa = OK
4 x aa = OK

USB runs at 5v. The max current you can draw is 500ma. Therefore the max load is 5v x 0.5A=2.5. Watts. (W=VxI) If you try and draw more than 500mA, you may overload the port which will cause it to break

Just a warning to look what your circuit needs if it needs higher this can break your ports

Or looking at a the transformer and see how many votls go in to the circuit ( if your 5 or under your ok )

and you can power of the Port :)

Most electronics nowadays are under 10 V and most of them Under 5V which is good for USB

Step 2: Get Your Cable

Okay so your going to need to get any USB cable this can be a printer cable or a MP3 player cable , your going to be cutting it up so don't pick a cable that you need :P

I chose this :

Step 3: Cutting

So you have your wire , now you will want to cut it to the length you want it , you only need the Male end so the other bit can be discarded

Step 4: Stripping the Wire

Okay you will want to strip the wire to reveal the wire underneath once you have done this there should be 4 wires , you only need the red and black ones as they are the power the green and white are data so they can go :)

Step 5: Soldering and Finish

So you will now want to solder the red wire ( positive ) and the Black Wire ( negative ) to the power in to your circuit or appliance as shown below you can also put heat shrink on the wires to make it neater :

So The Red is Positive ; +V

And the Black Negative ; 0V or -V

Step 6: Testing

Now you've done that you should be able to test it , just plug the cable into a USB port on a computer or laptop of choice , and see :)

Thanks for viewing my instructable