How can I provide more power to a DC motor that is in series behind a receiver circuit hacked out of a cheap RC car without burning up the receiver board? The board runs off two AAs at about 3V. I'm replacing the stock motor with a slightly larger one (12V, taken from a printer) and remounting it on a chassis for a homebrew robotics project... just messing around to learn more. I imagine I could go safely to 4.5V or even 6V with the receiver but I don't want to go much higher since half the stuff is epoxied and I can't really tell what's in there.
What I'd like to be able to do is add an additional two AA batteries behind the receiver to run the receiver system at 6V but add another two 3V 123A batteries to have the motor at 12V with the ability to run with the higher current draw due to the heavier load the motor will handle on its fancy new chassis... but without pulling that current through the receiver circuit.
My first thought is to simply connect my 123As negative to the motor and positive to a common ground... but I'm really not sure and I want to be careful to not damage the circuit or batteries. My next thought is to simply build a single power supply out of my 123As and use a current divider but I've only read about them and never actually tried so.
I've been doing some of those kiddie "electronic playgrounds," a few books and probably cost Google an extra few bucks in energy costs and I'm still kinda at a loss.