This simple project shows you how to make a USB powered Nokia cell phone charger. The advantage is that it weighs much less than the bulky AC adaptor, and can be used wherever you have a computer or a laptop. I use this thing all the time now!
What do I mean by “safe charger”? Honestly I’m not sure. I’m just going on what I was able to infer from what I read off my multimeter. What I found was that the voltage across the nokia charge pins was rapidly fluctuating from Vdd to about 4 volts above Vdd. It would not do to have ~9 volts injected into a 5 volt bus! Thankfully, all you need to do is stick a diode in there and that’s that. So the diode might not be needed, but it’s safe! Thus, “Safe Charger”.
So far, it charges my phone just fine, but slightly slower than the wall wart that came with it. I think so, anyway.
Step one: strip off the shielding and insulation on an inch or so of the usb cable. Clip the white and green cables to uneven lengths so they can’t conduct into each other or either of the power lines. Hopefully you should be left with a black wire and a red wire.
Step two: Clip off a length of the nokia chargers phone-side plug. You won’t be needing the wall wart part anymore. Strip off the insulation from the nokia plug wire. Hopefully you should have a red wire and a black one. the red wire should be connected to the inner barrel of the plug, and the black one should be connected to the outer barrel.
Step three: Attach a normal silicon diode (not a zener diode) with the line part towards the nokia plug. It should go between the red wires from both cables . Attach the black wires from each cable together.
I suggest staggering the lengths of the wires so that the solder joints have less chance of coming into contact.
Check all the wires with a multimeter to make sure they are really the right ones! The colors might not be standard...
Step four: cover that baby in hot glue! Yeah!
Step five: Cover that nogoodnick cable in electrical tape!
That’s it!