PowerSupply. - Here is Circuit Schematic 9v Battery Eliminator. If you use 9v battery powered devices for long periods of time, you may get tired of constantly changing batteries. The circuit below can be wired into any 9v battery powered device, drawing power from an external AC to DC power adapter. I designed the circuit around a very common LM317 adjustable voltage regulator.
The Original Article : "9v Battery Eliminator"