Complete design of electronic password lock based on single chip microcomputer

The circuit schematic is as follows:
 

The simulation schematic is as follows
 

Summary

In daily life and work, the security of residences and departments, the file archives of units, financial statements and the preservation of some personal information are mostly solved by locking. If traditional mechanical keys are used to unlock, people often need to carry multiple keys, which is extremely inconvenient to use, and the security is greatly reduced after the key is lost. It is an inevitable trend for electronic password locks with anti-theft alarm and other functions to replace mechanical password locks with small passwords and poor security. With the continuous development of science and technology, people have higher and higher requirements for safety and insurance devices in daily life. In order to meet people's requirements for the use of locks and increase their security, password locks that use passwords instead of keys came into being. Password locks have the advantages of high security, low cost, low power consumption, easy operation, and can be unlocked by remembering the password.

Most of the electronic password locks currently in use are based on single-chip microcomputer technology, with the single-chip microcomputer as the main component, and their encoders and decoders are generated by software.

This system consists of STC89C51 single-chip microcomputer system (mainly STC89C51 single-chip microcomputer minimum system), 4×4 matrix keyboard, LCD1602 display and alarm system, etc. It has the functions of setting and modifying six-digit user passwords, over-time alarm, over-time lock, and password error alarm (this design controls the LCD display by P0 port, and the correct password displays OPEN! The wrong password displays error! It will automatically lock after more than three wrong inputs. The matrix keyboard controlled by P1 port contains 0-9 numeric keys and AD function keys.). In addition to the above basic password lock function, remote control function can also be added according to actual situation. This system is low-cost and practical.

1.1. Background and significance of the subject

With the rapid development of electronic technology and computer technology, the performance of single-chip microcomputers has been continuously improved, the performance-price ratio has been significantly improved, and the technology has become more and more perfect. Because single-chip microcomputers have the characteristics of small size, light weight, low price, low power consumption, strong control function and fast computing speed, they have been widely used in various fields such as national economic construction, military and household appliances. This design uses a single-chip microcomputer and additional electronic components to realize data acquisition and control algorithms to complete a certain practical function, test and improve students' ability to design and grasp the overall circuit, understand the single-chip microcomputer system design process, and the actual production and debugging of circuit boards. At the same time, it also strengthens the practical application ability of digital circuits, single-chip microcomputers and microcomputer principles, and lays a theoretical and practical foundation for the further development of similar products.
With the improvement of people's living standards and the strengthening of safety awareness, the requirements for safety are getting higher and higher. Locks have been the iron generals guarding the door since ancient times. People have high requirements for them. They must be safe and reliable for anti-theft and easy to use. This is also the theme of lock makers for a long time. With the development of electronic technology, various electronic products have emerged, and electronic password locks are one of them. According to relevant information, the research on electronic password locks began in the 1930s and has been used in some special places for a long time. This lock completes the unlocking process by entering a set of passwords on the keyboard. The original intention of studying this lock is to improve the security of the lock. Because the key volume (password volume) of the electronic lock is very large, it can be used in conjunction with the mechanical lock, and it can avoid safety hazards caused by the key being copied. Electronic locks only require you to remember a set of passwords, and you don't need to carry metal keys, which saves people from the trouble of carrying metal keys, and is appreciated by more and more people. There are many types of electronic locks, such as digital locks, fingerprint locks, magnetic card locks, IC card locks, biometric locks, etc. But the most practical is the push-button electronic password lock.

After the 1980s, with the emergence of dedicated integrated circuits for electronic locks, the size of electronic locks has been reduced, the reliability has been improved, and the cost has been higher. They are suitable for use in occasions with higher security requirements and require a power supply. Their use is still limited to a certain range and is difficult to popularize, so there has been no significant progress in research on them.

At present, in developed Western countries, electronic password lock technology is relatively advanced and complete in variety. Electronic password locks have been widely used in intelligent access control systems, and door management is achieved through a variety of safer and more reliable technologies. The overall level of electronic locks in China is still around the 1970s internationally, and the cost of electronic password locks is still very high. The market is still dominated by key electronic locks. Key-type and card key-type electronic locks have introduced international advanced levels, and there are several factories in China that produce and supply the market. However, the market structure of electronic locks independently developed in China has not yet been formed, and their application is not yet widespread. Many domestic companies have also introduced advanced technologies in the world, and their development prospects are very impressive. It is hoped that through continuous efforts, electronic password locks can also be widely used in China.

1.2. Development trend of electronic password locks  

Electronic combination locks are used in the financial industry, and their fundamental role is "authorization", that is, only those who are "authorized" can deposit and withdraw money and goods. Broadly speaking, the "authorization" of the financial industry mainly includes the following three levels of content: 1. Granting custody rights, such as using safe deposit boxes, safes and safes; 2. Granting access rights, such as entering and exiting vaults, cash transport vehicles and storage rooms; 3. Granting circulation rights, such as automatic deposit and withdrawal. At present, the application of electronic combination locks in the financial industry is mainly concentrated on the first two levels. The following will introduce several electronic combination locks that are widely used in the financial industry and their technical development directions. Of course, no matter how advanced the authorization technology mentioned above is, it must be carried out by sophisticated "locks" as bearing structural components to realize the functions of opening and locking, and to bear the role of physical protection, resist or delay the destruction as much as possible, so that the electronic combination locks are "soft and hard". In general, the key to the anti-theft of locks is the strength of the lock body shell, the locked components, the locking type, the matching gap and the layout. The inevitable way to improve the protection ability of electronic password locks is to alarm. In many places in the financial industry, people are on duty, there are TV monitoring, and the alarm function can combine the two functions of physical prevention and human prevention. The premise of the alarm is to have a detection function. According to the use place and protection requirements of the electronic password lock, a variety of detection methods can be selected. In China's urban financial industry, the realization of networked alarm has become a basic requirement for various financial outlets. According to domestic and foreign practical experience, it is necessary for the financial industry to implement security risk levels, that is, based on the performance of the anti-theft alarm equipment used, the installation layout and the on-duty status of personnel, the protection ability of the protected object or area can be evaluated and the risk level can be obtained. Among them, the performance of the electronic password lock is crucial.

Since numbers, characters, graphics, images, human biometrics and time can all be electronic information of keys, the combined use of this information can make electronic combination locks highly confidential. For example, a heavily guarded vault requires an electronic combination lock with a composite information password, which is a "one foot taller than the thief". The combined use of information can also make electronic combination locks infinitely expandable and diversify products, which is "a thousand choices for the user, and they are satisfied with what they have".

Chapter 2 Determination of the overall design plan 2.1 Specific requirements for the design of electronic password locks

(1) To prevent password theft, this design requires that an asterisk be displayed on the LCD screen when the password is entered.

(2) Design an electronic combination lock with a six-digit unlocking password.

(3) The LCD display can show OPEN when the password is correct, ERROR when the password is incorrect, and INPUT PASSWORD when the password is entered.

(4) Implement electronic password lock if the wrong password is entered more than three times.

(5) 4×4 matrix keyboard including numeric keys 0-9, *, # and AD function keys