Intelligent door lock system retrofitted to existing door lock mechanism

An intelligent door lock system for a door retrofitted to an existing door lock system, comprising:

• an existing door lock system means including a lock device means with a lock means, and a drive shaft;
• and
• a intelligent door lock system means retrofitted to the existing door lock system means, the intelligent door lock system means coupled to the existing door lock system means to create a retrofitted intelligent door lock system means for locking and unlocking the door, the intelligent door lock system including:
• a position sensing device means configured to be coupled to the drive shaft means of the lock device means, the position sensing device means sensing position of the drive shaft means to assist in locking and unlocking the lock means of the lock device means;
• an engine means coupled to the positioning sensing device means;
• a circuit means coupled to the engine means,
• an energy source means coupled to the circuit means, and
• a device means that converts energy into mechanical energy coupled to the circuit means, positioning sensing device means and the drive shaft means, the device means that converts energy being coupled to the energy source means to receive energy from the energy source means;
• a wireless communication device means configured to be in communication with a mobile device means, and authorization is provided with the mobile device means to engage in locking or unlocking the door lock system means.