Intelligent monitor and electronic lock are placed in different places. If the communication line and the power supply line are separated, it is bound to increase the number of cable cores and increase security risks. The line multiplexing technology mentioned in this paper only uses a double-core cable to realize power supply and information transmission.

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 reduces the voltage of the received data signal and sends it to the demodulator to reduce the loss of the carrier signal in the transmission process. In order to reduce the interference between communication and power supply, the choice of choke L and coupling capacitor C should be considered comprehensively.

Let the carrier frequency fo=400kHz and L=33.7μH to ensure that most of the signal energy is transmitted to the receiving end. C 1=0.047 microfarad.

Second, the current monitoring technology

In order to prevent the excessive current flowing through the electromagnetic coil for some reason, which leads to the artificial destruction of communication lines and the burning of the electromagnetic coil by the electromagnetic actuator, the current monitoring technology is adopted in the design of the intelligent password lock.

Thirdly, data communication and preprocessing technology.

The intelligent monitor receives the status information sent by the lock (including lock opening and closing, first password error, second password error, third password error, etc.). ) and the current value flowing through the electromagnetic actuator coil, and read the power supply current value of the communication line at this time, which are combined to form a data block, in which the running state accounts for 1 byte, the power supply current accounts for 2 bytes, and the coil current accounts for 2 bytes.

The intelligent monitor is always in the receiving state during the communication with the electronic lock. In order to improve the communication reliability, the communication protocol adopts the way of repeated transmission, and each group of data of the electronic lock is repeatedly sent five times. After receiving this set of data, the intelligent monitor adopts large number decoding method to correct errors, which ensures the accuracy of data reception.

In addition, in order to save memory, the received data should be preprocessed, that is, after each data is received, it should be compared with the set threshold, and if it is greater than the threshold, it will send out an overrun alarm; If it is less than the threshold, compare the data with similar data received on the same day and keep the larger one. In this way, the data stored every day is the largest of its kind.

Extended data

Fingerprint is the uneven lines on the skin at the front end of the finger. Although fingerprints are only a small part of human skin, they contain a lot of information. Fingerprint features can be divided into two categories: overall features and local features.

General features refer to those features that can be directly observed by human eyes, including basic texture patterns, pattern areas, core points, triangular points, pattern lines and texture lines. The basic texture patterns are ring, bow and spiral.

Local features are the features of nodes on fingerprints, and these nodes with certain features are called feature points. Two fingerprints often have the same general features, but their local features-feature points-cannot be exactly the same. The feature points on the fingerprint are the endpoints, bifurcation points and turning points on the fingerprint line.

Fingerprint identification technology usually uses the general features of fingerprints, such as stripes and triangular points, to classify, and then uses local features, such as location and direction, to identify users.

Usually, "minutiae" are first found from the obtained fingerprint image, and then the digital representation of the user's living fingerprint-fingerprint feature data (one-way conversion, which can be converted from fingerprint image to feature data, but not from feature data to fingerprint image) is established according to the characteristics of minutiae.

Because two different fingerprints will not produce the same feature data, the similarity between the collected fingerprint image feature data and the fingerprint feature data stored in the database is calculated by pattern matching.

Finally, the matching results of the two fingerprints are obtained, and the user identity is identified according to the matching results. Because everyone's fingerprints are different, even between the ten fingers of the same person, there are obvious differences, so fingerprints can be used for identity identification.

Baidu encyclopedia-intelligent lock