Abstract: An automatic lock is disclosed. The lock can use a constant power spring to automatically lock itself when unlocked. The door lock can comprise a motor configured to charge a capacitor when a battery is depleted. The door lock can comprise a spindle extending from an exterior portion of the door lock to an interior portion of the door lock, mechanically linked to a key arm and a latch. When engaged, the key arm can allow the spindle to be turned by the exterior knob without actuating the latch, when disengaged, the key arm can allow the spindle to be turned by the exterior knob and actuate the latch.