I have a recently moved to the US, but my cellphone charger has a British plug. Therefore I have use an adapter, which makes the whole thing very cumbersome to carry around. As I always have some USB outlet like my laptop around anyways, I got the idea to make a USB version for charging the phone.
Step 1: Check the Power Adapter Voltage
Check what voltage the power adapter generates. For my Samsung model it is 5V DC, which is just what we want.
Step 4: Soldering
The little black insulating pieces are heat shrinkable tubing, which is very convenient. Just don't forget to put it on there.
Step 5: Charge Phone
Hooray, it works!