With the continuous development of human society and the continuous improvement of people's living standards, people's requirements for the quality of life are also higher and higher. However, people are also under great pressure in high paid jobs. They are often in a state of high mental tension after work. They may lose their work and often forget things, such as forgetting the key when they go out. They may also be other valuables. In order to avoid this phenomenon and give people a more comfortable, convenient and healthy life, The key chain manufacturer has designed a kind of anti-theft key chain, which can solve this kind of problem well and provide a safe and comfortable environment for people.

STC89C52 is used as the main controller, and two wireless modules nrf24loi are used as the transmitting module and the receiving module. When working, it can judge whether the anti-theft key chain is in the safe range by detecting whether the wireless transceiver module nrf24loi can transmit and receive signals normally. When the distance between the two modules is within the safe range, the receiving module can normally receive the signal from the transmitting module, and the data transmission is normal, then the system works normally, and the alarm circuit will not alarm: when the distance between the two modules exceeds the safe range, the receiving module cannot normally receive the signal from the transmitting module, The system can not carry out the normal data transmission, at this time the receiver will send an alarm signal, so as to play the role of anti-theft.

With the development of science and technology, the progress of society, people's pace of life is faster and faster, the living standard is also better and better, people have more spare money to buy, people buy high value things, in order to avoid the loss of these important things, reduce unnecessary losses, the emergence of anti-theft key chain factory will bring you more convenience.

Introduction of anti theft key chain

Lost key chain is a kind of anti-theft electric device in close range. It can avoid unnecessary loss of your valuable key due to negligence and theft, and give you a comfortable life. It adopts the principle of radio wave emission suppression. When it works, the panel sends out stable radio wave, and the main panel does not alarm after receiving the radio signal, When the distance between the main board and the pre board exceeds the predetermined distance, the main board can not receive the radio signal of the sub board, and immediately sends out an alarm sound to remind the user's attention.

working principle

STC89C52 is used as the main controller of the anti-theft keychain, and two wireless modules nrf24loj are used as the transmitting module and the receiving module respectively (the safety range is less than or equal to IO meters in the open space). Whether the anti-theft Keychain is in the safety range can be judged by detecting whether the wireless transceiver module nrf24loi can transmit and receive signals normally. When the distance between the two modules is within the "safe range" (less than or equal to 10 m), the system works normally and the data transmission is normal. If it is beyond the safe range, the system cannot transmit the normal data. At this time, the receiver will send out an alarm signal to remind the owner. The working process of the circuit is as follows: first, power on the receiving circuit to make the receiving module in the receiving state, Wait for the arrival of the data, and then run the program on the single chip microcomputer to transmit the data stored in the single chip register. If the distance between the transmitting module and the receiving module is within the "safe range", the receiving module will receive the signal within 1 ms and will not alarm. If it is beyond the "safe range", the receiving module will give an alarm by buzzer.

Features of anti theft key chain

1、 Easy to use

The anti-theft key is composed of two parts: the receiving module and the transmitting module. It is small in size, easy to carry, not to bring too much burden to people, and easy to use.

2、 Stable performance

Its anti-theft function is easy to use, and its alarm mode adopts the buzzer alarm. As long as the buzzer alarms, people can find it in the first time. In the design, the low power consumption design is used, and the light emitting diode is used as the voltage reminder. When the voltage is insufficient, the LED will light up to remind.

3、 Novel appearance

The appearance design of the machine is very small and beautiful, and it is green and environment-friendly, without radiation. It is powered by lithium battery and can be recharged for continuous use. The appearance of the anti-theft key chain is like a portable ornament, small and exquisite.