If you forget the lock screen password, you can restore the tablet to factory settings through double clearing. The specific steps are as follows:
The first step is to turn off the tablet first. When the tablet is turned off, press and hold the power button and the volume down button at the same time, and release them at the same time after 8 seconds. At this time, the tablet will enter the recovery English menu interface. Then select item 3: wipe data/factory reset:
Second step, then select the fourth option in the pop-up English dialog box: Yes, delete all user data:
The third step, then select the first item in the pop-up dialog box: Reboot system now, no power-on password is required after startup:
Extended information:
Password locked Basic Principle
Dial type
This is a fully mechanical combination lock with a large key capacity and high reliability without electronic components. Its operation method is unique, similar to the dialing of an old telephone - start from the starting point of the dial, turn the dial clockwise to a certain digit, and then return to the starting point to enter a password. Repeat this until the last digit of the code is entered, and then turn the dial counterclockwise from the starting point to unlock.
When the lock is unlocked, the interior has been reset. Therefore, after the dial returns to the starting point and the lock is closed, the password must be re-entered to unlock the lock. There is no need to consider the internal reset issue. If you enter the wrong password, you can also reset it internally by turning the dial counterclockwise (virtually unlocking the lock), and then re-enter the password.
In this kind of combination lock, the six-digit password can have more than 2.98 million sets of passwords for the owner to change at will, and the confidentiality is extremely high. The optional password groups are arranged in a row, making it easy to choose passwords that are easy to remember. The basic product that has been developed, the number of password digits and the amount of passwords can be redesigned according to user needs. Alarm interfaces can also be added for users.
Advantages of this combination lock:
1. No keys, no power supply, no batteries, and no waste pollutants.
2. It has a fully mechanical structure, can withstand quite harsh external environments, and has a wide range of uses.
3. The operation is simple and the unlocking time is relatively short. The average unlocking time is about 15 seconds.
4. The actual password volume is large and the confidentiality performance is high, and the probability of trial unlocking is almost zero.
5. Simple structure, strong and reliable.
Judging from the laws of technological development in history, when functions are similar, simple and reliable things always replace complicated things, and it is precisely the simplicity that replaces the complicated. Therefore, it is a popular and practical new product that should replace the traditional disc-type mechanical combination locks and some electronic combination locks.
Dial-type fully mechanical combination locks are suitable for safes, safes, file cabinets, antimagnetic fireproof cabinets, anti-theft doors, bank doors, warehouse doors, car doors, civil doors and mechanical blocking mechanisms. Widely used. It can replace the existing traditional disc-type mechanical combination locks and some electronic combination locks. Provides opportunities for updates of certain products.
Due to the popularity of electronic technology, many products are proud to use electronic structures. However, in some places, electronic products do not have absolute advantages. Instead, mechanical products or electromechanical hybrid products are more practical. Let’s take two examples: First, the ignition device for gas stoves. In the early days, transistor igniters were all the rage, but they were not resistant to moisture, were easily damaged, and were inseparable from batteries.
Over time, the mechanical (piezoelectric) ignition device that stores energy by twisting a knob by hand has shown its superiority - simple and practical, and has become the mainstream of gas stove igniters.
Second, car rearview mirrors and bus (single-cabin) rear door peepers were in danger of being replaced by electronic monitors, but people found that: traditional rearview mirrors and The observation effect of the ordinary rearview mirror above the driver of the bus is no worse than that of the electronic monitor, and it is simpler and more practical.
In fact, in traditional industries, you can also find investment directions that are safer than the so-called "new economy" but are no less profitable. The combination lock is not a product that is frequently used. It can be said to be a semi-static product, and the mechanical method is more practical.
However, the amount of passwords in electronic methods is large, and people subjectively feel safer.
The number of codes of this patented product is close to that of electronic code locks, and its operation is much faster than traditional mechanical code locks. It is simple and practical. It can be used like the two previous examples and is expected to become the mainstream of high-end code locks.
The dial-type fully mechanical combination lock is also a box-type mechanical combination lock, which is similar to the "Shajin" and "Logada" type box-type mechanical combination locks produced in the United States: they are both It is a disc-type mechanical combination lock with a control bolt and coaxial operation to input the password and open the bolt.
But the operation method is very different: the "Shajin" type box-type mechanical password lock is connected to the driving disk by the operating shaft, and then the driving disk drives other password disks in turn, so the knob needs to be turned when entering the password. Turn forward several times and then reverse several times to enter the password. The dial-type fully mechanical code lock relies on a simple sequence dialer inside to turn each code disc in sequence.
From the external operation point of view, it is similar to the operation of an old dial telephone: start from the starting point of the dial, turn the dial clockwise to a certain digit, and then return to the starting point to enter a number. bit password. Repeat this until the last digit of the password is entered, and then turn the dial counterclockwise from the starting point to open the lock tongue.
In addition, there are other differences between them:
1. The lock tongue unlocking bracket of the "Shajin" box-type mechanical combination lock is always pressed against the combination disc. When the password is entered, there will be a slight reflection when the disc gap rotates to the bracket. People with rich experience and high understanding can detect the password based on this feature.
The lock tongue unlocking bracket of the dial-type fully mechanical combination lock is separated from the combination disc when the password is entered. Only a small angle is pressed against the combination disc when unlocking, and At this time the password disk is stationary. Therefore, the probability of trying the password by touch is close to zero.
2. After closing the lock tongue of the "Shajin" type box-type mechanical combination lock, you need to manually turn the knob a few times to mess up the position of the combination disc, while the dial-type fully mechanical combination lock is in When the lock tongue is opened, the position of the password disc has been automatically moved (reset) internally. Therefore, after closing the lock tongue, the password must be re-entered to re-open the lock. The password will not be retained artificially.
3. The knob of the "Shajin" box-type mechanical combination lock must be engraved with 100 scales in 360 degrees. There is only an angle of 3.6 degrees between each scale. Be very careful when rotating the input.
The dial-type fully mechanical code lock only has 12 integer scales engraved in less than half a circle, and there is an interval of 12.5 degrees between each scale. When entering the password, it is allowed to be on the scale. Stay within the scale range of plus or minus 0.4, which allows the input of the integer value of the scale. Therefore it is a quasi-digital input. Its available passwords are arranged in order from the minimum value to the maximum value, and can be changed by the owner at will, without blind spots.
4. When entering the password for the dial type fully mechanical password lock, turn clockwise from the starting point to the last scale, which only takes 165 degrees, less than half a circle, and then return to the starting point and enter again. One digit password. During operation, you can hold the knob with one hand to input all passwords. Unlike the "Shajin" type box-type mechanical combination locks, which require several forward and reverse turns and frequent turnovers.
5. The number of code digits of the "Shajin" type box-type mechanical combination lock is fixed, while the number of code digits of the dial-type fully mechanical combination lock is variable. A password lock with a maximum password of 6 digits, and the number of password digits can be selected between 0-6 digits. If you choose a 3-digit password, it can only be limited to 3 digits. If you enter 4 digits, you cannot unlock the lock. This provides a wider range of choices for users in different places.
The dial-type fully mechanical combination lock with 12 scales and 6-digit password produced has 3.25 million sets of passwords. If it is changed to 7 digits, there will be 39.08 million passwords, and if it is 8 digits, there will be 430 million passwords. And all are optional passwords. If there are special needs for confidentiality, more scaled combination locks can be produced upon request.
Smart lock type
The smart password lock system consists of an intelligent monitor and an electronic lock, both of which are placed in different places. Line multiplexing technology is used here, so that only one two-core cable can be used for power supply and information transmission, which improves the reliability and safety of the system.
Basic principles and block diagram of intelligent monitor
Block diagram of intelligent monitor, which consists of microcontroller, clock, keyboard, LCD display, memory, demodulator, circuit It is composed of multiplexing and monitoring, A/D conversion, buzzer and other units. It mainly completes functions such as communication with electronic locks, intelligent analysis, and safety monitoring of communication lines.
At the sending end, the electronic lock boosts the modulated data signal through the pulse transformer T and sends it out; at the receiving end, the pulse transformer T steps down the received data signal and sends it to the demodulator. To reduce the loss of carrier signal during transmission. In order to reduce the mutual interference between communication and power supply, the selection of choke coil L and coupling capacitor C should be comprehensively considered.
Suppose the carrier frequency fo=400kHz. In order to ensure that most of the signal energy is transmitted to the receiving end, take L=33.7μH?C1=0.047μF.
Monitoring technology
In order to prevent the artificial destruction of communication lines and the electromagnetic actuator from burning the coil due to excessive current flowing through the electromagnetic coil for some reason, this article discusses the design of smart password locks Current monitoring technology is used. The current monitor uses the current/voltage conversion chip MAX471 produced by MAXIM Company.
This chip can convert the measured current I into the ground output voltage U, and has the characteristics of large measurement range, high accuracy, and the output voltage U is proportional to the measured current I. The output voltage of the current monitor is sent to the A/D converter. By reading the A/D conversion result, the microcontroller learns the changes in the current in the line, detects abnormalities in time through analysis, and issues an alarm signal.
Processing technology
The smart monitor receives the status information from the lock (including the lock's opening, closing, the first wrong password, the second wrong password, the third time Incorrect password, etc.), the current value flowing through the electromagnetic actuator coil, and reading the power supply current value of the communication line at that moment. The three are combined to form a data block, in which the operating status occupies 1 byte and the power supply current occupies 2 Bytes, the coil current occupies 2 bytes.
The smart monitor is always in the receiving state during communication with the electronic lock. In order to improve the reliability of communication, this article adopts the method of repeated transmission in the communication protocol. The electronic lock repeatedly sends each set of data 5 times. After the intelligent monitor receives this set of data, it uses the law of large number decoding to correct errors, ensuring Accuracy of data received.
In addition, in order to save memory, preprocessing technology needs to be used for the received data. That is, after each piece of data is received, the data is first compared with the set threshold value. If it is greater than the threshold value, then Issue an over-limit alarm; if it is less than the threshold value, compare the data with similar data received on the day, and retain the larger one. In this way, the data stored every day is the maximum value among similar data.
Intelligent analysis
Intelligent analysis and prediction technology is based on the data block received each time. Compare the recorded values ??of the data, analyze the size and trend of current changes caused by the operation, promptly discover problems, and report them to managers, thereby improving the reliability of the entire system.
System software
The intelligent password lock software uses 51 series microcontroller assembly language to program the intelligent monitor and electronic locks respectively. The intelligent monitor software includes modules such as keyboard scanning and LCD display program, buzzer driver, clock modification and reading program, data communication and preprocessing program, intelligent analysis program and line monitoring program.
Electronic lock software includes keyboard scanning and decoding programs, LCD display programs, communication programs, electromagnetic actuator driving and detection programs, sensor interface programs and other modules. The modular design method is adopted in the software design process to facilitate the reading, debugging and improvement of the program.
The intelligent password lock makes full use of the 51 system microcontroller software and hardware resources, introduces intelligent analysis functions, and improves the reliability and security of the system. After being installed and used in a certain model of safe, it is welcomed by users.
In addition, with slight changes in software and hardware, smart password locks can form an intelligent distributed monitoring network to achieve centralized monitoring and management within a certain range. It has broad application prospects in other security fields. The smart monitor is always in the receiving state and receives alarm information and status information from the electronic lock in a fixed format.
For alarm information, an audible and visual alarm will be issued immediately through the LCD display and buzzer; for status information, it will be stored in the memory and compared with the historical status of the electronic lock before this moment to obtain Identify changing trends, predict future state changes, and provide corresponding information to personnel on duty through the LCD display for decision-making.
While establishing communication with the electronic lock, the intelligent monitor monitors changes in the power supply current flowing through the communication line in real time through the A/D converter, effectively preventing damage caused by human factors and ensuring communication The line is smooth.
Basic Principle
The block diagram of an electronic lock. It is also based on the 51 series microcontroller (AT89051) as the core and equipped with corresponding hardware circuits to complete the setting, storage, identification and processing of passwords. Display, drive electromagnetic actuator and detect its driving current value, receive alarm signals from sensors, send data and other functions.
The microcontroller receives the typed code and compares it with the password stored in the EEPROM. If the password is correct, it drives the electromagnetic actuator to unlock; if the password is incorrect, the operator is allowed to re-enter the password, up to It can be entered three times; if it is incorrect three times, the microcontroller will alarm the intelligent monitor through the communication line.
The microcontroller sends each unlocking operation and the driving current value of the electromagnetic actuator as status information to the smart monitor. At the same time, the alarm information received from the sensor interface is also sent to the smart monitor as a smart monitor. basis for chemical analysis.
Baidu Encyclopedia-Password Lock