Application of human proximity sensor in ATM cash machine monitoring

1. Overview

　　Human proximity sensor, also known as contactless proximity sensor, is an ideal electronic switch sensor. When the metal detection body approaches the sensing area of ​​the sensor, the switch can issue electrical instructions quickly without contact, pressure, or sparks, accurately reflecting the position and stroke of the motion mechanism. Even if it is used for general stroke control, its positioning accuracy, operating frequency, service life, convenience of installation and adjustment, and adaptability to harsh environments are incomparable to general mechanical stroke switches. It is widely used in machine tools, metallurgy, chemical industry, textile and printing industries. It can be used as a limit, counting, positioning control and automatic protection link in the automatic control system. The proximity sensor has the characteristics of long service life, reliable operation, high repeated positioning accuracy, no mechanical wear, no sparks, no noise, and strong vibration resistance. Therefore, so far, the application range of proximity sensors has become increasingly wide, and the speed of its own development and innovation is also extremely rapid.

　　As a means of technical defense, human proximity sensors have been gradually recognized and applied by people. In order to better implement the national standard GB/T10488-1997 human proximity sensors and make more people understand the principles and applications of human proximity sensors, this paper introduces the basic knowledge about the principles and applications of human proximity sensors based on the human proximity sensors developed and produced by Nanjing Yuantuo Technology.

　　Application of human proximity sensor in ATM cash machine monitoring:

　　ATM dedicated human proximity sensor YTMW8631 and human activity monitor YT-EWS, a control device for detecting human proximity, can accurately detect the approach of nearby people, and is currently the best choice for alarm and status detection. The sensing part has a high detection sensitivity to the movement of nearby people, and suppresses the sound signals of the surrounding environment, and has a strong interference ability. It can be widely used in anti-theft devices in ATM, insurance and other occasions. It is easy to install and can be installed horizontally or vertically. The sensitivity to human induction is continuously adjustable, which makes the human proximity sensor adaptable to many different occasions.

　　It is widely used in finance, industry, self-service banking, ATM monitoring human proximity alarm, etc. It uses microcircuit chips for program control processing, with high detection sensitivity and trigger reliability. The detection and control parts are combined into one, with low standby power consumption, switch signal output, direct triggering of alarm recording, and easy to use.

　　Performance characteristics:

　　(1) It has the function of penetrating walls and non-metallic doors and windows, and is suitable for concealed built-in installation of bank ATM monitoring systems;

　　(2) The distance of human body approach detection can be adjusted, and the adjustable radius is (approximately) 0-5 meters;

　　(3) The detection area is double-sector shaped, covering a large space range;

　　(4) Double comparison of the amplitude and width of the detection signal is performed to reduce false alarms;

　　(5) It has high adaptability to ambient temperature and does not affect the detection sensitivity at -20 to 50 degrees Celsius.

　　(6) Non-contact detection.

　　(7) Not affected by temperature, humidity, noise, airflow, dust, light, etc., suitable for harsh environments.

　　(8) Strong anti-RF interference capability.

　　2. Classification and structure of Yuantuo Technology's human proximity sensor

　　2.1 Two-wire proximity sensor

　　The two-wire proximity sensor is easy to install and wire; it is widely used, but it has the disadvantages of large residual voltage and leakage current.

　　2.2 DC three-wire

　　There are two types of DC three-wire proximity sensors: NPN and PNP. In the 1970s, most Japanese products were NPN output, while Western European countries had both NPN and PNP output types. PNP output proximity sensors are generally used in PLCs or computers as control instructions, while NPN output proximity sensors are mostly used to control DC relays. In actual applications, the output form should be selected according to the characteristics of the control circuit.

　　3 Selection and detection of proximity sensors

　　3.1

　　Different types of proximity sensors should be selected for different materials and different detection distances to achieve high performance-price ratio in the system. Therefore, the following principles should be followed in the selection:

　　3.1.1 When the detection object is a metal material, a high-frequency oscillation proximity sensor should be selected. This type of proximity sensor is most sensitive to iron-nickel and A3 steel detection objects. Its detection sensitivity is low for aluminum, brass and stainless steel detection objects.

　　3.1.2 When the detection object is a non-metallic material, such as wood, paper, plastic, glass and water, a capacitive proximity sensor should be used.

　　3.1.3 When metal and non-metal objects need to be detected and controlled at a long distance, photoelectric proximity sensors or ultrasonic proximity sensors should be used.

　　Let's analyze the way of video recording triggering. Many manufacturers now use "motion detection" as a typical way to trigger alarm recording. Let's briefly analyze that most ATM teller machines are installed facing the street, where the flow of people and vehicles is unpredictable. In this case, motion detection is almost useless, resulting in a large number of invalid junk video files. The result is a large number of junk videos that are difficult to find, and the hard disk will not stop working for a long time, accelerating its damage.

　　Next, we take an ATM branch with a good transaction volume as an example, and assume that each branch has 200 transactions per day. From the above data, we can see that when motion detection is used as a recording trigger, the proportion of invalid recording files is very large, and it is very inconvenient to review the required recordings. On the contrary, when the recording is triggered by a human activity monitor, the generation of invalid recording files is almost eliminated, which is very convenient for reviewing recordings and collecting evidence in the future.

　　What is the working principle of Yuantuo Technology's human proximity sensor?

　　① There is a high-frequency transmitter in the human proximity sensor, which causes the coil to emit a high-frequency magnetic field.

　　② When the object being tested is close to a high-frequency magnetic field, eddy currents will be generated on the surface of the object being tested, and the eddy currents will induce a magnetic field in the opposite direction.

　　③ The transmitter stops vibrating because the magnetic field caused by the eddy current cancels out the effect.

　　④ The control output is turned on/off by the presence or absence of vibration.

　　Among all kinds of switches, there is a kind of component that has the ability to "sense" objects approaching it - displacement sensor. The purpose of controlling the switch on or off is to use the displacement sensor's sensitive characteristics to approaching objects. This is the proximity switch.

　　Because displacement sensors can be made according to different principles and methods, and different displacement sensors have different ways of "sensing" objects, the common proximity switches are as follows:

　　Eddy current proximity switch, capacitive proximity switch, Hall proximity switch, photoelectric proximity switch, pyroelectric proximity switch, other types of proximity switches

　　The main uses are:

　　Nanjing Yuantuo Technology's human proximity sensors and human activity monitors are widely used in bank ATM triggering surveillance video, aviation, aerospace technology, safes and industrial production. In daily life, they are used in automatic doors and automatic hot air blowers in hotels, restaurants and garages. In terms of security and anti-theft, important places such as data archives, accounting, finance, museums, and vaults are usually equipped with anti-theft devices composed of various proximity switches. In measurement technology, such as length and position measurement; in control technology, such as displacement, speed, and acceleration measurement and control, a large number of proximity switches are also used.