Just a minor warning about Wall-Warts:
Some are AC (no rectification)
Some are half-wave rectified DC (with, or without an internal filter capacitor)
Some are full-wave rectified DC (with, or without an internal filter capacitor)
Most are unregulated, and in fact they purposely have a high output impedance so that they will not burn up if shorted (part of UL Certification)
Some are regulated, but have fairly modest output current ratings.
Most are not suitable for running low-voltage, high-current motors...