The working principle of the battery-free NFC smart lock mainly involves two aspects: energy harvesting and communication interaction:
A. Energy Harvesting:
1. NFC Field Energy Harvesting: When an NFC-enabled mobile phone or other NFC-enabled read/write device is close to the battery-free NFC smart lock, it will generate an NFC RF field around it. The NFC chip or related components inside the smart lock can sense this RF field and harvest energy from it. This energy harvesting method makes use of the principle of electromagnetic induction, similar to the primary coil (NFC reading and writing device) in a transformer generates a changing magnetic field, which induces an electric potential in the secondary coil (the NFC receiving part of the smart lock), thus providing the smart lock with the power needed for its work.
2. Energy Storage and Conversion: The collected energy will be stored in the capacitors or other energy storage elements inside the smart lock. These energy storage elements can store the instantly collected energy and convert and condition it to meet the working voltage and current requirements of the internal circuits and chips of the smart lock. For example, unstable AC power is converted to stable DC power for use by the control circuits and actuators of the smart lock.
B. Communication interaction:
1. Authentication Information Transmission: After the mobile phone or NFC read/write device establishes an NFC connection with the smart lock, it will transmit data containing user authentication information to the smart lock. This information can be the digital key pre-stored in the mobile phone, encrypted user information and so on. After receiving this information, the smart lock will decrypt and verify it to determine whether the user has the authority to unlock the door2.
2. Transmission and execution of control instructions: If the user's identity is verified, the mobile phone or NFC read/write device will send control instructions to the smart lock to open or close the lock. After receiving these instructions, the control circuit inside the smart lock will drive the actuator (e.g., motor, electromagnetic lock, etc.) to carry out the corresponding operation to achieve the opening or closing of the lock.
In short, the battery-free NFC smart lock realises the unlocking operation without external power supply by cleverly using the energy collection and communication function of NFC technology, which is convenient for users and avoids the maintenance and replacement problems brought by batteries.
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