hi im trying to so some mods to a gameboy pocket. Im trying to backlight the screen (im using the backlight panel from a treo 700p screen) and im trying to make the system rumble whenever sound plays. i have the motor and when you wire it directly to the battery source it runs fine im just trying to find a way to make it only rumble when a sound plays. Ive tried every possible audio connection and either its not powerful enough or it just rumbles all the time. Is there a way to make a circuit that has the motor hooked up to the vcc but only give power to the motor when the sound is coming from the left or right audio out like on the pro sound mod? im still someone new to this stuff so any help would be appreciated

Just a guess... Maybe you could hook up a transistor with its gate connected to the audio source so that the motor would turn full on when the gate voltage gets high enough to turn on transistor?

I tried that but it seems like the faint power being given off by the left or right channel isnt enough to open the gate.

I do have another question though. I managed to get a ds lite battery inside of the gameboy pocket and it powers it fine. I have it connected to the power jack on the bottom of it. When i go to charge the battery ive been plugging in the regular gameboy pocket charger. Is this safe or is there a chance of the battery overcharging? ( i dont know if the ds lite battery has overcharge protection). Sorry if im asking noob questions im new to trying to mod things.

Not sure about your batteries question but as for gameboy rumble...

taken directly from acidmods

I'm not sure if this is too long ago to bump, but I was recently doing the same thing. There's a huge danger, since it will just continue to charge, and probably do bad stuff, like everything that overcharges does. The solution, http://www.dealextreme.com/details.dx/sku.26114

I'm not quite handy enough to make one of my own, and that thing is pretty small. It should fit with no troubles, I got it inside a DMG.