Keeping Cell Phones On And Connected... not as easy as it seems

**trader007** · 04-02-2011, 04:47 PM

having a bit of trouble finding a way to keep my cellphone on and connected to my computer in the car.

the problem is the software im using, i cant let the phone reboot because that would require me to start up the internet sharing software manually everytime i get in the car. not to mention the phone is slow when the battery is near 0%, so its best to keep it charged.

i also have to use usb connection for the data, so i cant just keep the phone plugged into a 12v adapter.

i think what im going to have to actually do is physically switch the phone from the computer to the 12v always-on adapter when the computer shuts off. that way the phone can charge while the car is parked, and when the car turns on the phone switches to the computer usb.

monoprice has this usb switch- http://www.monoprice.com/products/pr...mat=4#feedback

i dont think it would be that hard to use a transistor to activate that pushbutton switch... it would have dummy logic since it wouldnt know whats switched a or b, but i would think it would stay synced with my actions once i get it right....

anyone have better ideas? (btw, i tried splicing usb cables. i had the data wires go to the computer, and the power wires cut off and went to a 12v usb adapter. the phone doesnt charge in high amp mode, the phone somehow knows its not getting power from the computer. and when the computer is off, the data wires are not grounded together so the phone still wont charge the battery).

**PaulF** · 04-02-2011, 05:16 PM

The cable hacking method didn't work because the phone expects a certain resistance across the data pins to enable charging.

Anyway...

If you find a device that has a physical switch rather than a toggle button, you could pretty much trigger it with a relay attached to the computer's 12 volt rail.

**trader007** · 04-02-2011, 08:05 PM

well it actually seems to be working now. i think what was hanging me up is this phone doesnt go into fast charge mode with less then 2% battery life remaining. i thought it should work because when the pc turns off im pretty sure the motherboard shorts out the data pins to allow devices to charge with the computer in standby.

so now i just have to get the 12v power adapter onto a time delay relay, so it turns off after a few hours of the car sitting parked. this will give the phone time to charge even if i just go on short trips everyday.