Design And Development Of Fingerprint Lock

With the development of science and technology,people concern more and more with security since their living standards are continuously improved.As an important security tool,door lock has been paid more and more attention.The old mechanical lock is out of date because the key is bulky,easy to copy and lose,it can’t meet people’s demand for safety and convenience.A fingerprint combination lock is designed and developed which is easy to operate,safe and reliable with different classification of user rights which is expounded systematically in this thesis from the aspects of structure,hardware circuit,control software and so on.Through testing,the experimental lock can achieve the designed goal.First,the structure system of the fingerprint combination lock is studied.The security control scheme of fingerprint combination lock is designed through the verification program to validate whether the fingerprint or password the user input is valid or not so as to realize the purpose of the unlocking.The core of the fingerprint combination lock is fingerprint sensor for which this thesis puts forward two plans.One plan is choosing capacitive semiconductor sensor.Although it is small in size,good in image quality,and self-adaptive to various fingerprints,it is expensive,easy to be damaged by wear and complex in structure design.The other one is using optical fingerprint sensor,which is cheap and can offset some other disadvantages of capacitor semiconductor sensor.So our final choice is optical fingerprint sensor model ZFM708SA50H,and the core touch chip is model MPR121.In addition,the power supply module,the display module,the voice module,the motor drive module,the clock module,the storage module,the control unit module and the touch display-lamp module are also analyzed in this article before the design scheme is determined.Second,the hardware circuit and software system of the fingerprint combination lock are developed.The hardware circuit design mainly includes:the power supply circuit,single-chip microcomputer minimum system circuit,fingerprints,touch circuit,power supply voltage detection circuit,clock circuit,voice circuit,data storage circuit,LED display circuit,touch indicator light circuit,motor drive circuit and so on.The development of software system realizes the following functions:system initialization function,low power consumption wake-up processing function,set up key wake-up processing function,voice wake-up function,fingerprint wake-up processing function,touch wake-up processing function,system menu management function and so on.Finally,the physical testing of fingerprint combination lock we developed and designed is completed.Test results show that the fingerprint combination lock has completely reached the design target.The hardware performance of the fingerprint combination lock is good,stable and reliable when running,and the software system is stable with nice fingerprint recognition.Since the combination lock has successfully met the indicators requirements,it can be formally put into production.