iPhone 3G DIY USB convertor
Introduction
Further to the Bluetooth Car Kit I reviewed on my previous post I found that the USB port did NOT charge the iPhone 3G. I had read somewhere that the iPhone requires reference voltages on the data + / - pins. So I did some googling and came across a great circuit schematic.
Circuit Diagram
Here is the circuit I used as reference : diagram
Parts
I went to down to my local Jaycar and picked up the following items.
- 47K 1% tolerance resistor
- 33K 1% tolerance resistor
- 33K 1% tolerance resistor
- 22K 1% tolerance resistor
- Small DIY PCBoard
- Small black box housing
- Female USB socket
This set me back about $14AUD but considering there is nothing like this on the market here in Australia I figured I had nothing to lose.
I scounged around for a spare USB cable that had a male plug. I stripped it and prepared the positive +5v and ground wires, red and black (respectively). I then placed the resistors on the board and soldered them into place.
I used the excess wire from the resistors to complete the wiring as per the diagram. I had to bend the outer edges of the female socket flat for fitting in the housing later. I then soldered the female usb socket in place. I soldered the usb cables +5v and ground to the pc board and was ready to go.
I prepared the housing using an art & craft scalpel to make a hole for both the usb male cable and the usb femail socket. I had to cut the PCB board to fit before I could solidly mount it in the housing.
I placed some spare packaging from a memory sodimm to keep the PCB board in place then closed off the housing with the included screws + rubber feet. Being the lame-o I am sometimes, I decided to pretty it up a little and printed off a label to stick on the front which I sticky-taped on.
Of course I tested that it worked before I sealed up the housing. I used my PC to test that the iPhone actually did charge. Essentially the PC's usb hub was providing a +5v and a ground to my converter which then made two reference voltages of 2.8V and 2.0V to the + and - data pins (respectively). Those two reference voltages are what trigger the iPhone to switch from battery to mains and use the converter to start charging.
I mounted it in my car and connected it to my Bluetooth Car Kit. Charged no problems. I hid the wiring a little and now just need a black iPhone USB cable to appear less noticeable than the standard white one I used in the photos.
Further to the Bluetooth Car Kit I reviewed on my previous post I found that the USB port did NOT charge the iPhone 3G. I had read somewhere that the iPhone requires reference voltages on the data + / - pins. So I did some googling and came across a great circuit schematic.
Circuit Diagram
Here is the circuit I used as reference : diagram
Parts
I went to down to my local Jaycar and picked up the following items.
- 47K 1% tolerance resistor
- 33K 1% tolerance resistor
- 33K 1% tolerance resistor
- 22K 1% tolerance resistor
- Small DIY PCBoard
- Small black box housing
- Female USB socket
This set me back about $14AUD but considering there is nothing like this on the market here in Australia I figured I had nothing to lose.
I scounged around for a spare USB cable that had a male plug. I stripped it and prepared the positive +5v and ground wires, red and black (respectively). I then placed the resistors on the board and soldered them into place.
I used the excess wire from the resistors to complete the wiring as per the diagram. I had to bend the outer edges of the female socket flat for fitting in the housing later. I then soldered the female usb socket in place. I soldered the usb cables +5v and ground to the pc board and was ready to go.
I prepared the housing using an art & craft scalpel to make a hole for both the usb male cable and the usb femail socket. I had to cut the PCB board to fit before I could solidly mount it in the housing.
I placed some spare packaging from a memory sodimm to keep the PCB board in place then closed off the housing with the included screws + rubber feet. Being the lame-o I am sometimes, I decided to pretty it up a little and printed off a label to stick on the front which I sticky-taped on.Of course I tested that it worked before I sealed up the housing. I used my PC to test that the iPhone actually did charge. Essentially the PC's usb hub was providing a +5v and a ground to my converter which then made two reference voltages of 2.8V and 2.0V to the + and - data pins (respectively). Those two reference voltages are what trigger the iPhone to switch from battery to mains and use the converter to start charging.
I mounted it in my car and connected it to my Bluetooth Car Kit. Charged no problems. I hid the wiring a little and now just need a black iPhone USB cable to appear less noticeable than the standard white one I used in the photos.
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