Infrared, laser, millimeter wave... Which is the future of smart lock sensors?

Release time:

2024-08-03

Reprinted from wechat platform public number - Research group - Intelligent door lock research.If the hardware device wants to become intelligent, it cannot be separated from the help of sensors, and the smart lock is also the same.

Infrared, laser, millimeter wave... Which is the future of smart lock sensors?

If the hardware device wants to become intelligent, it cannot be separated from the help of sensors, and the smart lock is also the same. Through sensors, the smart lock can "sense" the surrounding situation and make various behaviors based on the feedback. For example, the face recognition function wakes up in advance, the opening and closing of the welcome light, and the wandering alarm detection, etc., so that users can experience the real intelligent security.
The process of smart lock, hardware and software has been constantly developing, at present, there are many types of sensors on the market are applied to the door lock, their characteristics are different, the specific performance is not the same. Some lock friends said that there are many types of smart lock sensing, and it is unclear where the difference is.
To this end, Smart Door Lock Research Pro has invited relevant practitioners in the industry to bring you the relevant knowledge about smart lock sensors.

Smart lock sensor type

At present, there are mainly three kinds of sensors on the smart lock market: infrared, LiDAR (TOF, structured light) and millimeter-wave radar. Although the same sensor, but the principle and application between the obvious difference.

❶ Infrared

The principle of infrared sensors is to use infrared transmitters to emit infrared rays at a certain Angle. The receiver receives the signal at a certain Angle, and the sensing distance is determined according to the transmission and reception angles. Infrared sensors are widely used in medicine, military, environmental and other fields have a large number of applications, is a very common sensor, such as common temperature gun, infrared thermal imager and so on.

Compared with other sensors, infrared sensors have low cost, simple structure, sensitive response and other advantages. But at the same time, the infrared measurement distance and accuracy performance is relatively poor, and the color of the object to be measured has requirements, sensitive to white, black is not sensitive (that is, light is easily absorbed by black, not easily captured by the receiver).

❷ Laser radar

There are two main types of liDAR sensors, single point TOF and structured light. The principle of TOF is that the laser emitter tube emits infrared laser, the receiver calculates the time difference between transmission and acceptance, and the distance can be calculated according to the speed of light. The distance is determined by calculating the size of the spot emitted by the laser emitter.

Laser radar has a high measurement accuracy, at the same time, can obtain the depth information of the measured object, high precision. But at the same time, lidar is more expensive and susceptible to environmental factors, such as sunlight, rain, fog and so on.

❸ Millimeter wave radar

Millimeter wave refers to the working wavelength of 1 ~ 10mm band, the principle is that the transmitter emits millimeter wave, the receiver calculates the distance through the Doppler effect.

The Doppler effect means that the wavelength of an object's radiation changes because of the relative motion of the source and the observer. In front of the moving wave source, the wave is compressed, the wavelength becomes shorter, and the frequency becomes higher. When behind a moving wave source, the wavelength becomes longer and the frequency becomes lower; The higher the velocity of the wave source, the greater the effect. From the degree of the wave red (or blue) shift, the speed at which the wave source is moving in the observed direction can be calculated.

Millimeter wave radar can penetrate smoke, fog, dust, anti-interference ability is strong, and is not affected by the appearance of the measured object. However, millimeter wave radar has high power consumption and higher measurement accuracy than infrared, but it is not as good as Lidar. In terms of cost, millimeter-wave radar is somewhere between infrared and lidar.

Sensor application

The above describes the advantages and disadvantages of the three sensors commonly used in smart locks. So at present, which kind of mainstream smart lock is mainly used? From the perspective of power consumption, cost, accuracy and anti-interference, the above sensor characteristics can be seen in the following table:

As can be seen from the above table, infrared is not as good as the other two in terms of accuracy or anti-interference, only power consumption and cost advantages are obvious. Lidar and millimeter-wave radar both cost more and consume more power than infrared. However, the product accuracy and anti-interference ability are stronger than infrared.

According to the observation of the mainstream smart lock manufacturers' products on the market, most products are mainly millimeter wave radar, a small number of liDAR, and infrared is almost not used. This is because the millimeter wave radar has a strong anti-interference ability, can adapt to the changing use environment, the measurement accuracy is moderate, and it is a product with a relatively balanced cost performance and function. Lidar is also used by manufacturers because of its low power consumption. But the high cost makes the application scope less than the other two. Although the accuracy and anti-interference ability of the infrared sensor are relatively poor, because the cost is relatively low, it can be seen on some smart locks with very low prices.

To sum up, with the development of smart lock products, Lidar and millimeter-wave radar are undoubtedly the big trend. From the application situation of manufacturers, cost-effective millimeter wave radar or will be the future trend. Although the millimeter-wave radar power consumption is high, most of the current locks use large-capacity lithium batteries, and the power reserve is large, so power consumption is not a big problem. With the large number of applications of millimeter wave radar, it will further promote product progress, reduce costs, and achieve full popularity.

Special thanks
Thank Mr. He of Zhongshan Hanxin Technology Co., Ltd. for providing technical support to this article

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