I've seen several USB charger projects online and these work well for most devices that charge off of USB, but never quite worked for my fifth generation Ipod. Most of these chargers are
based off of the LM7805 voltage regulator, in order to step a voltage down to the 5V required for USB. What these designs lack is the data in-out signal that tells the 5G Ipod that it is a high power USB outlet. I recently found a suggestion online to use 4 equal resistors to make a voltage divider to supply a 2.5V signal to each data line on the usb connector. Check out the thread where I found it
here for more details. Anywho, I used the bread board on my Parallax BOE-Bot to prototype the circuit for testing. You may notice that there is no LM7805 on this circuit. That's because the BOE-Bot has one integrated into it, which sped up my testing. After verifying that I did
indeed get 2.5V on the data lines I plugged in the Ipod. Previously the Ipod needed to be reset in order to charge on such a circuit, but now it charges as if it were plugged into a real USB outlet. Now I just need to figure out if the LM7805 will hold up to the rigors of being wired into my truck's 12V power so that I can make a charger to integrate into the Ipod car dock that I'm slowly designing.
based off of the LM7805 voltage regulator, in order to step a voltage down to the 5V required for USB. What these designs lack is the data in-out signal that tells the 5G Ipod that it is a high power USB outlet. I recently found a suggestion online to use 4 equal resistors to make a voltage divider to supply a 2.5V signal to each data line on the usb connector. Check out the thread where I found it here for more details. Anywho, I used the bread board on my Parallax BOE-Bot to prototype the circuit for testing. You may notice that there is no LM7805 on this circuit. That's because the BOE-Bot has one integrated into it, which sped up my testing. After verifying that I did
indeed get 2.5V on the data lines I plugged in the Ipod. Previously the Ipod needed to be reset in order to charge on such a circuit, but now it charges as if it were plugged into a real USB outlet. Now I just need to figure out if the LM7805 will hold up to the rigors of being wired into my truck's 12V power so that I can make a charger to integrate into the Ipod car dock that I'm slowly designing.
