I plan to drive a 3-4.5V rated brush DC motor with a Pololu DRV3388; generate sounds on a small 16 ohm speaker, and motion control with a Pololu 3001HB servo. I’ve elected to run on 2 packs of 3 cell 1.5V rechargeable batteries, both providing about 3.6v each. My Seeeduino Duemilanove board will be driven from the battery packs in series through the onboard power jack, while taping off one 3.6V pack for the DC motor. I’m isolating the speaker with a 2N2222 (or equivalent) so I can drive the 500 mW rated speaker to about 400 mw.
The Seeeduino board has a forward bias diode driving a 78M05 5 volt regulator (making the 7.2V input marginal). What is not shown in this diagram are 3 noise suppression caps on the DC motor. I will also have an I2C 3 axis accelerometer and several other analog and digital I/O devices running off the 5V onboard regulator. I’ll be doing wireless development using an Adafruit XBee Adapter kit so that is not shown either. Eventually I’ll probably use a DPST power switch so I can switch both battery packs.
I’m very new to Fritzing so the drawing is not to my satisfaction (I had to retouch connections for clarity). If I create a PCB I might change GPIO pin assignments.