DIY iPhone Charger

Finally, after a few weeks of waiting, I’ve managed to proof that my iPhone charger concept works! Special thanks to Jia Ying who helped me buy components from Pudu. Here’s how to build your own iPhone charger:



All you need are the 4 resistors stated above. I have modified some values of the resistors because of some miscalculation. Connect them as shown and provide the circuit with a regulated 5v supply. Get a female USB plug and connect it as shown to the circuit. Make sure the positive and negative terminals are connected correctly. The D+ and D- pins have low currents so connecting them wrongly may not blow up your iPhone.

Once you are done, triple-check your circuit. Use a voltmeter to make sure everything is correct. Then plug in your iPhone and you should be greeted with the charging chime, indicating that your iPhone is now charging properly.

Practical application: In-car iPhone charger.

A normal cheap car USB charger.

I have tons of USB car chargers lying around because it seems like every device that I buy comes with one free. These chargers are very simple in construction. They take in 12V and they output a regulated 5V to the USB ports. These cheap chargers will not work with the iPhone because the D+ and D- pins are not connected. I can remember at least one incident when I need to charge my iPhone but couldn’t because I didn’t have the proper car charger.

This charger is a bit special because it uses switching (pulse width modulation) to get 5V from 12V.

So with the circuit diagram above, I constructed the voltage divider circuit and put it into the charger. It’s wrapped in tape to prevent it from shorting.

It works!

Now I can charge my iPhone when I’m traveling long distances.

Other practical applications: External battery.

Get a high capacity battery (8.4v @ 3000mah for example) and use a 7805 to regulate it to 5v. Then feed it to the circuit above and you’ll be able to charge your iPhone when you’re not in a car or near a wall socket. If you use 6 AA batteries (9v), you can charge your iPhone anyplace where you can find batteries. That’s almost anywhere in the world! The days of running out of juice is over!

Disclaimer: I will not be responsible if you destroy you iPhone with the information posted here. I have tested the circuit and it works perfectly with my iPhone. If you plan to build this circuit, please triple-check everything before plugging your iPhone in. Happy charging!

Update: DIY iPhone 3G charger. Also explained: why the iPhone charges when reference voltages are applied. Continue reading