A coin recognition and detection system based on three-coil multi-band detection

Abstract

This invention is a coin detection system, comprising an eddy current sensor installed on a coin travel channel to emit magnetic field lines into the channel. When a coin passes through the magnetic field lines, a corresponding output signal is generated, and the system simultaneously senses changes in the magnetic field as the coin passes. The system includes an eddy current sensor control unit for controlling the operating frequency of the eddy current sensor according to control signals from a main control unit; a signal conditioning unit for conditioning the output signal of the eddy current sensor according to control signals from the main control unit; a digital signal conversion unit for converting the magnetic field changes sensed by the eddy current sensor into eddy current loss and inductance data; and a main control unit for determining the authenticity and face value of the coin based on the signals from the eddy current sensor and the eddy current loss and inductance data output by the digital signal conversion unit. This invention features self-regulating operation by controlling the eddy current sensor to operate at a range of suitable frequencies through the eddy current sensor control unit and the lift-off effect generated after the inductively coupled impedance sensor is controlled by the digital signal conversion unit. This eliminates the need for manual operation, providing significant convenience to the user.

Description

Technical Field

[0001] This invention belongs to the field of coin processing equipment, specifically a coin recognition and detection system based on three-coil multi-frequency band detection. Background Technology

[0002] Currently, banks and related financial institutions, as well as public transportation companies and shopping malls in my country, use coin detection equipment such as coin exchange machines and coin sorting machines. These devices are required to distinguish genuine coins from counterfeits and identify their face value. Detecting the material characteristics of coins is a common method for identifying genuine coins from counterfeits and identifying their face value. Most manufacturers in the industry currently use the eddy current detection principle. Eddy currents can distinguish coins of different materials, sizes, and thicknesses by emitting electromagnetic waves in three frequency bands (high, medium, and low). However, eddy currents alone have certain limitations. Firstly, they are not very effective at detecting surface coatings. Secondly, the number of sampling points is limited. According to the applicant, existing eddy current detection devices involve independent AD conversion circuits that convert analog data from sampling points into digital data, which is then sent to the main chip for data analysis. The number of sampling points, the number of conversions by the AD chip, and the data transmission method all affect the speed of counterfeit detection. Therefore, the number of sampling points is generally limited to no more than six, which increases the difficulty of distinguishing between coins of different currencies and makes it impossible to define the characteristic range for counterfeit detection. Summary of the Invention

[0003] In view of the above-mentioned shortcomings in the existing technology, the purpose of the present invention is to provide a coin detection system and method for accurately and stably detecting the material characteristics of coins.

[0004] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0005] A coin recognition and detection system based on three-coil multi-band detection includes:

[0006] An eddy current sensor is installed on the coin passageway to emit magnetic field lines into the coin passageway. When a coin passes through the magnetic field lines, a corresponding output signal is generated through the magnetic field lines passing through the coin, and at the same time, the change in the magnetic field when the coin passes through is sensed.

[0007] The eddy current sensor control unit is used to control the operating frequency of the eddy current sensor according to the control signal from the main control unit.

[0008] The signal conditioning unit is used to condition the output signal of the eddy current sensor according to the control signal of the main control unit;

[0009] The digital signal conversion unit is used to convert the magnetic field changes sensed by the eddy current sensor into eddy loss and inductance data;

[0010] The main control unit is used to determine the authenticity and face value of a coin based on the signal from the eddy current sensor and the eddy loss and inductance data output by the digital signal conversion unit.

[0011] The eddy current sensor also includes an inductive impedance sensor unit, which generates a magnetic field of a specific frequency through the coil plate wires and senses the change in magnetic field caused by the lift-off effect when the coin passes through through the magnetic field detection element.

[0012] The impedance sensor unit includes a coil plate with coil plate wires arranged in a spiral pattern from the outside to the inside. A magnetic field detection element is provided at one end of the coil plate. Both the coil plate wires and the magnetic field detection element are electrically connected to the digital signal conversion unit.

[0013] The eddy current sensor control unit consists of an interface circuit and a switching circuit connected in sequence. The interface circuit is connected to the eddy current sensor, and the switching circuit is connected to the main control unit. The switching circuit performs on and off operations according to the control signal of the main control unit to control the operating frequency of the eddy current sensor.

[0014] The signal conditioning unit includes a signal amplification circuit and a parameter adjustment circuit, wherein...

[0015] The parameter adjustment circuit is used to receive control signals from the main control unit to set the amplification factor of the signal amplification circuit;

[0016] The signal amplification circuit is connected to the receiving coil of the eddy current sensor and the AD peripheral of the main control unit, respectively. It is used to filter, amplify and shape the output signal of the eddy current sensor to the set range according to the control signal received by the parameter adjustment circuit.

[0017] The digital signal conversion unit includes an inductive digital sensor U4 and its peripheral circuitry. The clock signal pin SCLK, chip select signal pin CSB, and data input / output pins SDI and SDO of the U4 are all connected to the main control unit via an SPI interface for transmitting impedance data. The interrupt output pin INTB of the U4 is connected to the external I / O port of the main control unit with interrupt functionality via a resistor R10, enabling the main control unit to distinguish the material of different coins based on the time difference between the rising edge at the start of the conversion and the falling edge at the end of the conversion.

[0018] A coin recognition and detection method based on three-coil multi-band detection includes the following steps:

[0019] The eddy current sensor control unit controls the operating frequency of the eddy current sensor through interface circuits and switching circuits based on the control signals from the main control unit.

[0020] The signal conditioning unit filters, amplifies, and shapes the output signal of the eddy current sensor, conditioning its peak value to the range of 2.5V to 3.2V.

[0021] The signal conditioning unit samples the conditioned signal according to the sampling frequency output by the main control unit and transmits the sampled signal to the main control unit.

[0022] The main control unit controls the digital signal conversion unit to start, causing the inductive impedance sensor to generate a magnetic field of a specific frequency, and converts the magnetic field change caused by the passing of the coin into digital quantities of eddy loss and inductance, which are then transmitted to the main control unit.

[0023] The main control unit uses data sampled by the eddy current sensor, as well as eddy loss and inductance data, to determine the face value and authenticity of the coin.

[0024] The process of converting the sensed magnetic field change caused by the passing of the coin into digital quantities of eddy loss and inductance is specifically as follows:

[0025] When a coin approaches the inductive impedance sensor unit, the digital signal conversion unit starts the conversion, and the interrupt output pin INTB changes from low to high. After the CPU pin of the main control unit detects the level change, it starts recording the current time, which is t1. When the conversion is completed, the interrupt output pin INTB changes from high to low, and the CPU pin of the main control unit detects the level change and starts recording the current time, which is t2. This time is used to characterize the different inductive impedance caused by different coins arriving at the magnetic field. The conversion time t = t2 - t1 is calculated, and t is used as the inductive impedance value.

[0026] The main control unit determines the denomination and authenticity of the coin by sampling data from the eddy current sensor and data on eddy current loss and inductance. Specifically:

[0027] The data characteristics of the eddy current sensor sampling data, as well as the eddy current loss and inductance data, are compared with the characteristics in the genuine coin feature database to determine the face value and authenticity of the coin to be detected.

[0028] An eddy current sensor includes a magnetic transmitting module and a magnetic receiving module, with a detection gap formed between the magnetic transmitting module and the magnetic receiving module to allow a coin to pass through; the magnetic receiving module has a secondary detection module near the detection gap, the secondary detection module includes a coil plate, coil plate wires are arranged on the coil plate, and a magnetic field detection element is provided at one end of the coil plate; the coil plate wires and the magnetic field detection element are both electrically connected to a digital signal conversion unit, and the digital signal conversion unit is electrically connected to a main control unit.

[0029] The coil board conductors are arranged in a layered, spiral shape from the outside in on the coil board.

[0030] The coil board has two cable connection ends at one end, and the two cable connection ends are electrically connected to the digital signal conversion unit through corresponding connection cables. One cable connection end is connected to the outer wire end of the coil board conductor, and the other cable connection end is connected to the inner wire end of the coil board conductor.

[0031] The magnetic transmitting module is equipped with a transmitting end temperature measuring element, and the magnetic receiving module is equipped with a receiving end temperature measuring element.

[0032] The magnetic emission module includes a transmitter core and a transmitter base. A first coil is wound on the transmitter core, and the transmitter core and the first coil are disposed together in the transmitter base. A transmitter back cover and a transmitter cable are provided on the rear side of the transmitter base, and the first coil is electrically connected to the eddy current sensor control unit through the transmitter cable.

[0033] The magnetic receiving module includes a receiving magnetic core and a receiving base. A second coil is wound on the receiving magnetic core, and the receiving magnetic core and the second coil are disposed together in the receiving base. A receiving back cover and a receiving cable are provided on the rear side of the receiving base, and the second coil is electrically connected to the signal conditioning unit through the receiving cable.

[0034] Both the eddy current sensor control unit and the signal conditioning unit are electrically connected to the main control unit.

[0035] The magnetic transmitting module is disposed in the first base, and the magnetic receiving module is disposed in the second base. The upper ends of the first base and the upper ends of the second base are fixedly connected. The secondary detection module includes a fixed baffle, and the fixed baffle is disposed on the side of the second base near the detection gap. The coil plate is fixed by the fixed baffle.

[0036] The first mounting body has a first mounting cavity inside, and the magnetic emission module is embedded in the first mounting cavity. The rear side of the first mounting cavity is closed by a first cover plate. One end of the first mounting cavity has a first through hole, and one end of the second mounting body has a second through hole, and the second through hole is connected to the first through hole. A cable guide is provided in the second through hole, and the front end of the cable guide is placed in the first through hole. The transmitting cable on the magnetic emission module passes through the cable guide and is bent out.

[0037] The second mounting body has a second mounting cavity inside, and the magnetic receiving module is embedded in the second mounting cavity. The rear side of the second mounting cavity is closed by a second cover plate. The receiving cable on the magnetic receiving module is led out from the lower opening of the second mounting cavity.

[0038] The present invention has the following beneficial effects and advantages:

[0039] 1. It can control the eddy current sensor to operate at a suitable frequency point based on the stored reference through the eddy current sensor control unit, without manual intervention and with strong temperature adaptability.

[0040] 2. The signal output of the eddy current sensor is adjusted to a suitable range by the signal conditioning unit to make the detection results more accurate.

[0041] 3. By integrating and optimizing the circuit structure, the main control unit CPU peripheral is used for data acquisition and conversion. After eliminating the time for external AD sampling and transmitting the sampled results to the main control unit CPU, the processing time of the main control unit CPU is increased from 6 points in the industry to 30 points, making the sampling more refined and reducing interference and jitter in the sampling process.

[0042] 4. Based on the lift-off effect principle, the eddy loss and inductance values ​​are obtained by controlling the digital signal conversion unit and the quasi-transformed inductive impedance sensor on the metal surface to transform the magnetic field of the coating.

[0043] 5. It has a simple interface with the external CPU control system, making it easy to control and implement. Attached Figure Description

[0044] Figure 1 A schematic diagram of the structure of this invention;

[0045] Figure 2 Schematic diagram of the installation location of the eddy current sensor;

[0046] Figure 3 Circuit diagram of the eddy current sensor control unit;

[0047] Figure 4 Signal conditioning unit circuit diagram;

[0048] Figure 5 Digital signal conversion unit circuit diagram;

[0049] Figure 6 This is a cross-sectional view of the structure of an eddy current sensor.

[0050] Figure 7 for Figure 6 Exploded view of the eddy current sensor;

[0051] Figure 8 for Figure 6 A schematic diagram showing the interaction between the magnetic transmitter module and the magnetic receiver module;

[0052] Figure 9 for Figure 8 A schematic diagram of the magnetic field lines generated between the magnetic transmitting module and the magnetic receiving module;

[0053] Figure 10 for Figure 6 Schematic diagram of the intermediate coil plate;

[0054] Wherein, 1 is the first base, 101 is the first cover plate, 102 is the first through hole, and 103 is the first mounting cavity; 2 is the second base, 201 is the second cover plate, 202 is the cable guide, and 203 is the second through hole; 3 is the magnetic transmitting module, 301 is the transmitting magnetic core, 302 is the transmitting base, 303 is the transmitting rear cover, 304 is the transmitting cable, and 305 is the transmitting temperature measuring element; 4 is the magnetic receiving module, 401 is the receiving magnetic core, 402 is the receiving base, 403 is the receiving rear cover, 404 is the receiving cable, and 405 is the receiving temperature measuring element; 5 is the secondary detection module, 501 is the fixing baffle, 502 is the connecting cable, 503 is the coil board, 5031 is the coil board wire, and 5032 is the cable connection end; 6 is the coin track; 7 is the digital signal conversion unit, 701 is the connection pin, and 702 is the detection pin. Detailed Implementation

[0055] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0056] A coin recognition and detection system based on three-coil multi-band detection includes:

[0057] An eddy current sensor is installed on the coin passageway and emits magnetic lines of force to the coins passing through the passageway, generating a corresponding output signal through the magnetic force of the coins.

[0058] The output of the eddy current sensor control unit is connected to the eddy current sensor, and the input is connected to the signal acquisition unit. After the signal acquisition unit completes the signal filtering and amplification, the final output is connected to the main control unit to control the operating frequency of the eddy current sensor under the control of the main control unit.

[0059] The signal conditioning unit has its input end connected to the eddy current sensor and its output end connected to the main control unit. It is used to filter, amplify, and condition the output signal reference of the eddy current sensor under the control of the main control unit.

[0060] The digital signal conversion unit is installed on the coin passage. After a specific frequency magnetic field is generated by the inductive impedance sensor, the magnetic lines of force are transmitted to the coin passing through the coin passage. The coin's magnetic force generates a lift-off effect, and the change in the magnetic field is sensed again by the inductive impedance sensor and transmitted to the digital signal conversion unit. The magnetic field transformation is converted into specific numbers of eddy loss and inductance and then transmitted to the main control unit.

[0061] The main control unit is used to determine the authenticity and face value of the coin based on the signal output from the sampling unit and the data from the signal conditioning unit.

[0062] The eddy current sensor control unit includes an interface circuit and a switching circuit that are interconnected. The interface circuit is used to connect to the eddy current sensor, and the switching circuit is connected to the main control unit and is used to perform on / off operations under the control of the main control unit, thereby controlling the operating frequency of the eddy current sensor.

[0063] The sampling frequency, A / D conversion accuracy, and reference waveform of the signal conditioning unit are controlled by the main control unit.

[0064] The activation and conversion rate of the digital signal conversion unit are controlled by the main control unit.

[0065] The main control unit uses a three-dimensional feature pattern recognition method to determine the face value and authenticity of coins.

[0066] A coin detection method includes the following steps:

[0067] Based on different operating conditions such as temperature and humidity of the equipment environment, the main control unit controls the eddy current sensor control unit to perform reference adjustment on the eddy current sensor according to the stored basic waveform, so that it works at the corresponding operating frequency.

[0068] The signal conditioning unit conditions the peak values ​​of the three frequency segments of the output signal of the eddy current sensor to 2.5V-3.2V; the signal conditioning unit samples the output signal of the signal conditioning unit according to the sampling frequency provided by the main control unit, and the sampled signal is transmitted to the main control unit for multi-point sampling at the sampling frequency and data conversion at the A / D conversion accuracy.

[0069] The digital signal conversion unit transmits the magnetic field lines generated by the inductive impedance sensor at a specific frequency to the coin passing through the coin passage. The magnetic force of the coin generates a lift-off effect, and the change in the magnetic field after being sensed again by the inductive impedance sensor is transmitted to the digital signal conversion unit. The digital signal conversion unit converts the change in the magnetic field into specific numbers of eddy loss and inductance and then transmits them to the main control unit.

[0070] The main control unit uses a three-dimensional feature pattern recognition method to determine the face value and authenticity of coins. This pattern recognition method establishes a genuine coin feature database, compares the features of the coin to be detected with those features in the database, and then determines the face value and authenticity of the coin.

[0071] Figure 1This is a schematic diagram of an embodiment of the present invention. It includes: an eddy current sensor, a signal conditioning unit, an inductive impedance sensor, a digital signal conversion unit, an eddy current sensor control unit, and a main control unit. An eddy current sensor is installed on the coin transport channel, emitting magnetic lines of force onto the coins passing through the channel. The magnetic lines of force transmitted through the coins generate a corresponding output electrical signal. The output of the eddy current sensor control unit is connected to the eddy current sensor, and its input is connected to the main control unit. This control unit controls the operating frequency of the eddy current sensor. The input of the signal conditioning unit is connected to both the eddy current sensor and the main control unit. This unit, under the control of the main control unit, conditions the output signal of the eddy current sensor using a reference waveform. The input of the signal conditioning unit is connected to the main control unit, and its output is connected to the main control unit. This unit, under the control of the main control unit, sets the number of acquisition frequencies and the AD conversion accuracy of the signal output from the signal conditioning unit, and performs data conversion. The main control unit then performs preliminary comparison of the 30-frequency data of the three-band eddy current transmission signal with the coin feature points in the genuine coin feature database to determine the authenticity and face value of the coin. The main control unit then controls the digital signal conversion unit to turn on the oscillation switch of the inductive impedance sensor coil. The digital signal conversion unit converts the self-inductance transformation of the inductive impedance sensor in the magnetic field into specific digital quantities of eddy loss and inductance, and then transmits them to the main control unit. The converted eddy loss and inductance data are then compared with the coin feature points in the genuine coin feature database to determine whether the coin's coin features match those of a genuine coin. By combining the comparison of the three types of data in the two comparisons, the authenticity and face value of the coin are determined.

[0072] like Figure 2 As shown, eddy current sensors are installed on both sides of the coin sliding channel. The coin passes between the magnetic signal transmitting part and the magnetic signal receiving part of the magnetic core of the eddy current sensor on the coin sliding channel.

[0073] like Figure 3 As shown, the eddy current sensor control unit includes an interface circuit and a switching circuit connected to each other. The interface circuit is used to connect the eddy current sensor, and the switching circuit is connected to the main control unit to perform on / off operations under the control of the main control unit, thereby controlling the operating frequency of the eddy current sensor. The working principle of the eddy current sensor control unit is as follows: the main control unit controls the on / off of MOS transistors Q1 and Q2 through the interface circuits RSMALL and RNIG, so that the eddy current sensor operates at a suitable frequency and performs real-time sampling data processing on the passing coins.

[0074] like Figure 4As shown, the working principle of the signal conditioning unit is as follows: the external CPU controls the parameter adjustment circuit through the interface circuit to make the signal amplification circuit work at a suitable amplification factor. This means that the output signal of the eddy current sensor is filtered, amplified, and shaped by the signal amplification circuit, so that the amplified and shaped output signal is within the range of 2.5V--3.1V. This allows the eddy current sensor signal to obtain error compensation, adjusts the output signal of the eddy current sensor to a suitable range, and makes the detection results more accurate.

[0075] like Figure 5 As shown in the diagram, pins 1 and 2 of socket P3 are connected to the inductive impedance sensor unit; pins 1 (SCK_BOTTOM, NSS_BOTTOM, MOSI_BOTTOM, and MISO_BOTTOM) of chip U4 are connected to the SPI interface of the main control chip; pin 16 (INT_BOTTOM) of chip U4 is connected to the I / O port of the main control chip with interrupt peripheral function (interrupt I / O has the characteristics of high real-time performance, can interrupt the CPU program execution, and is used for time pulse detection with low latency). The digital signal conversion unit will give the inductive impedance sensor unit a fixed high-frequency pulse excitation, and then the inductive impedance sensor unit, which uses its own coil, senses the change in the magnetic field previously emitted, transmits the electrical signal to the digital signal conversion unit, and after conversion by the digital signal conversion unit, sends the current inductive reactance and impedance data to the main control via the SPI signal. The detection resolution of the inductive reactance data in this data is low, and it cannot provide detailed data that can support coin identification. Through a large number of experiments, it was found that when the digital signal conversion unit completes the conversion, the level of the INT_BOTTOM pin will change from high to low. Moreover, the conversion rule bit changes immediately after each data conversion is completed. After analyzing the time from the high level of the conversion to the low level after the conversion is completed, it was found that its value has good distinguishability for different types of metal coins, and the consistency of the same type of coin is good. Ultimately, the duration of the rising and falling edges of the pin's level transition is used to distinguish coins. When the transition is enabled, the INT_BOTTOM pin changes from low to high. After the main chip's CPU pin detects the level change, it starts recording the current time t1. After the transition ends, the pin changes from high to low. After the main chip's CPU pin detects the level change, it starts recording the current time t2. The transition time t = t2 - t1. This value can be interpreted as the inductive reactance value. Since different inductive reactance values ​​will cause the analog chip inside the sensor chip to process different inductive reactances in different times, the falling edge time t2 represents the different inductive reactance values ​​brought about by the detection of different coins arriving at the magnetic field. The transition time t value can represent the result after the inductive reactance is converted.

[0076] When a coin approaches the impedance sensor unit, the CPU receives the impedance value from the digital signal conversion unit. The corresponding time when the INT_BOTTOM pin level changes after the digital signal conversion unit completes the conversion is similar to the peak or trough of a sine wave (the peak and trough will vary depending on the type of coin). The generation of the highest or lowest point is analyzed through continuous acquisition as a basis for judging the characteristics of the coin.

[0077] In this embodiment, the following eddy current sensor can be used:

[0078] like Figures 1-2 and Figures 6-10 As shown, the eddy current sensor includes a first base 1 and a second base 2. The first base 1 is equipped with a magnetic transmitting module 3, and the second base 2 is equipped with a magnetic receiving module 4. A detection gap is formed between the magnetic transmitting module 3 and the magnetic receiving module 4 to allow a coin to pass through. The upper ends of the first base 1 and the second base 2 are fixedly connected. Figures 6-8 As shown, the magnetic receiving module 4 has a secondary detection module 5 located near the detection gap. Additionally, the magnetic transmitting module 3 has a transmitting end temperature measuring element 305 on its outer side, and the magnetic receiving module 4 has a receiving end temperature measuring element 405 on its outer side. Both the first base 1 and the second base 2 are made of plastic to ensure insulation. The transmitting end temperature measuring element 305 and the receiving end temperature measuring element 405 can be thermistors, and the number and position of the thermistors are set according to actual needs.

[0079] like Figures 6-8 and Figure 10 As shown, the secondary detection module 5 includes a coil plate 503, and coil plate wires 5031 are arranged on the coil plate 503. One end of the coil plate 503 is provided with a magnetic field detection element 5033 (a commercially available product); Figure 1 As shown, the detection and control system includes a digital signal conversion unit 7, and the magnetic field detection element 5033 on the coil plate 503 is electrically connected to the digital signal conversion unit 7. At the same time, one end of the coil plate 503 is provided with two cable connection ends 5032. The two cable connection ends 5032 are electrically connected to the digital signal conversion unit 7 through corresponding connection cables 502. In addition, one cable connection end 5032 is connected to the outer wire end of the coil plate wire 5031, and the other cable connection end 5032 is connected to the inner wire end of the coil plate wire 5031.

[0080] like Figure 2As shown, when the eddy current sensor is working, when a coin passes through the detection gap between the magnetic emission module 3 and the magnetic receiving module 4 along the coin track 6, the magnetic receiving module 4 will generate a corresponding output signal to the signal conditioning unit. After the signal conditioning unit completes the signal processing, it will transmit the processed data to the main control unit. The main control unit will compare the received signal data with the corresponding coin feature value in the genuine coin feature database, thereby realizing the preliminary detection of the coin. The above process is the same as the prior art, for example, see patent CN204423492U.

[0081] However, in addition to the preliminary detection mentioned above, the main control unit of the eddy current sensor also controls the digital signal conversion unit 7 to activate the secondary detection module 5, specifically as follows: Figure 10 and Figures 1-2 As shown, the digital signal conversion unit applies current to the coil plate wire 5031 on the coil plate 503 to generate an alternating magnetic field. When this magnetic field acts on the surface of the coin, it induces eddy currents. The reverse magnetic field generated by the eddy currents is superimposed on the magnetic field around the coil plate 503, which changes the magnetic field distribution around the coil plate 503. The magnetic field detection element 5031 integrated on the coil plate 503 detects the changes in the magnetic field around the coil plate 503 in real time (such as the attenuation of the magnetic field amplitude) and outputs the corresponding detection signal to the digital signal conversion unit. The digital signal conversion unit processes the detection signal and sends it to the main control unit. The main control unit compares the feature parameters with the standard feature values ​​of the corresponding coin in the genuine coin feature library to further identify coin characteristics (such as the characteristics of the surface metal plating).

[0082] In the eddy current sensor, the detection distance between the coil plate 503 and the coin is 1 mm. Additionally, as shown... Figure 10 As shown, the coil plate wires 5031 are arranged in a layered, spiraling shape from the outside in on the coil plate 503. The spacing between adjacent layers of the coil plate wires 5031 is 4 mil (i.e., 0.1016 mm), and the thickness of the coil plate 503 is 1.2 mm. The coil plate 503 can also be configured as a multi-layer structure, with each layer having the same structure and each having coil plate wires 5031 arranged in a layered, spiraling shape from the outside in. The detection accuracy of the secondary detection module 5 mainly depends on factors such as the size of the coil plate 503, the density of the coil plate wires 5031, and the distance between the coil plate wires 5031 and the coin. Through the above design, the eddy current sensor enables the alternating magnetic field generated by the coil plate wires 5031 to form eddy currents on the surface of the coin. Furthermore, the reverse magnetic field generated by the eddy currents, when superimposed with the magnetic field around the coil plate 503, can form a sufficient magnetic field change, which can then be detected by the magnetic field detection element 5031.

[0083] like Figure 1 and Figures 6-9As shown, in the eddy current sensor, the magnetic emission module 3 includes an emission core 301 and an emission base 302. The emission core 301 is made of long-ring ferrite, and a first coil is wound on the emission core 301. The emission core 301 and the first coil are disposed together in the emission base 302. The emission base 302 has an emission rear cover 303 and an emission cable 304 on its rear side, and the emission cable 304 realizes the electrical connection between the first coil and the eddy current sensor control unit. In the eddy current sensor, the emission base 302 is made of plastic.

[0084] like Figures 6-9 As shown, in the eddy current sensor, the magnetic receiving module 4 includes a receiving magnetic core 401 and a receiving base 402. The receiving magnetic core 401 is made of long-ring ferrite, and a second coil is wound around the receiving magnetic core 401. The receiving magnetic core 401 and the second coil are together housed in the receiving base 402. A receiving rear cover 403 and a receiving cable 404 are provided on the rear side of the receiving base 402, and the receiving cable 404 provides electrical connection between the second coil and the signal conditioning unit. In the eddy current sensor, the receiving base 402 is made of plastic.

[0085] The magnetic field lines between the magnetic transmitting module 3 and the magnetic receiving module 4 are as follows: Figure 9 As shown, the magnetic emission module 3 generates magnetic field lines perpendicular to the upper surface, and the magnetic receiving module 4 receives unblocked magnetic field lines and magnetic field lines transmitted through the coin. The outer ring of the magnetic receiving module 4 forms returning magnetic field lines. When a current is applied to the first coil of the magnetic emission module 3, an alternating magnetic field is generated. When the coin passes through the detection gap between the magnetic emission module 3 and the magnetic receiving module 4, eddy currents are generated, which in turn cause a change in the magnetic field. The second coil of the magnetic receiving module 4 generates an induced signal due to the change in the magnetic field. The signal is amplified and shaped by the signal conditioning unit and then transmitted to the main control unit. The above are all technologies known in the art, for example, see patent CN204423492U.

[0086] like Figures 6-7 As shown, in the eddy current sensor, the first base 1 has a first mounting cavity 103 inside, and the magnetic emission module 3 is embedded in the first mounting cavity 103. The rear side of the first mounting cavity 103 is closed by a first cover plate 101.

[0087] like Figures 6-7As shown, in the eddy current sensor, the bottom end of the first mounting cavity 103 is provided with a first through hole 102, and the second base 2 is provided with a second through hole 203 at one end, and the second through hole 203 is correspondingly connected to the first through hole 102; a cable guide 202 is provided in the second through hole 203, and the front end of the cable guide 202 is placed in the first through hole 102; the transmitting cable 304 passes through the cable guide 202, thereby achieving a 90-degree bend and lead-out.

[0088] like Figures 6-7 As shown, in the eddy current sensor, the second base 2 has a second mounting cavity inside, and the magnetic receiving module 4 is embedded in the second mounting cavity. The rear side of the second mounting cavity is closed by the second cover plate 201, and the lower end of the second mounting cavity forms an opening for the receiving cable 404 to be led out.

[0089] like Figures 6-8 As shown, in the eddy current sensor, the secondary detection module 5 includes a fixed baffle 501, which is located on the side of the second base 2 near the detection gap. The coil plate 503 is fixed by the fixed baffle 501. In the eddy current sensor, the fixed baffle 501 is made of plastic.

[0090] The working principle of the eddy current sensor is as follows:

[0091] When the eddy current sensor is working, the detection process is as follows when a coin passes through the detection gap between the magnetic emission module 3 and the magnetic receiving module 4 along the coin track 6:

[0092] 1. The main control unit controls the first coil on the magnetic emission module 3 to apply current to generate a magnetic field. When a coin passes through the detection gap between the magnetic emission module 3 and the magnetic receiving module 4, eddy currents are generated, which in turn cause a change in the magnetic field. The second coil on the magnetic receiving module 4 is thus induced to generate a corresponding signal. The signal is amplified and shaped by the signal conditioning unit and then transmitted to the main control unit.

[0093] Second: The main control unit compares the received signal data with the corresponding coin feature value points in the genuine coin feature database, thereby realizing the overall detection of the coin to determine its authenticity and size.

[0094] Third: At this time, the coin is still in the detection gap. The main control unit controls the digital signal conversion unit 7 to start the working state of the secondary detection module 5. That is, the digital signal conversion unit 7 controls the digital signal conversion unit 7 to apply current to the coil board wire 5031 on the coil board 503 to generate an alternating magnetic field. When the magnetic field acts on the surface of the coin, eddy currents are induced. The reverse magnetic field generated by the eddy currents is superimposed on the magnetic field around the coil board 503, which will change the magnetic field distribution around the coil board 503. The magnetic field detection element 5031 integrated on the coil board 503 detects the changes in the magnetic field around the coil board 503 in real time (such as magnetic field amplitude attenuation) and outputs the corresponding detection signal to the digital signal conversion unit for processing.

[0095] Fourth, the digital signal conversion unit processes the detection signal and sends it to the main control unit. The main control unit compares the feature parameters with the standard feature values ​​of the corresponding currency in the genuine coin feature library for a second time to further identify coin characteristics (such as surface metal plating characteristics).

[0096] In addition, when the equipment is working continuously or under special circumstances such as complex changes in ambient temperature, the temperature measuring element 305 at the transmitting end will detect the temperature of the magnetic transmitting module 3 in real time, and the temperature measuring element 405 at the receiving end will detect the temperature of the magnetic receiving module 4 in real time. Once the detected temperature change exceeds the set range value, the equipment system can alarm to prompt the staff to perform timely calibration.

Claims

1. A coin recognition and detection system based on three-coil multi-band detection, characterized in that, include: An eddy current sensor is installed on the coin passageway to emit magnetic field lines into the coin passageway. When a coin passes through the magnetic field lines, a corresponding output signal is generated through the magnetic field lines passing through the coin, and at the same time, the change in the magnetic field when the coin passes through is sensed. The eddy current sensor control unit is used to control the operating frequency of the eddy current sensor according to the control signal from the main control unit. The signal conditioning unit is used to condition the output signal of the eddy current sensor according to the control signal of the main control unit; The digital signal conversion unit is used to convert the magnetic field changes sensed by the eddy current sensor into eddy loss and inductance data; The main control unit is used to determine the authenticity and face value of a coin based on the signal from the eddy current sensor and the eddy loss and inductance data output by the digital signal conversion unit.

2. The coin recognition and detection system based on three-coil multi-band detection according to claim 1, characterized in that, The eddy current sensor also includes an inductive impedance sensor unit, which generates a magnetic field of a specific frequency through the coil plate wires and senses the change in magnetic field caused by the lift-off effect when the coin passes through through the magnetic field detection element.

3. The coin recognition and detection system based on three-coil multi-band detection according to claim 2, characterized in that, The impedance sensor unit includes a coil plate with coil plate wires arranged in a spiral pattern from the outside to the inside. A magnetic field detection element is provided at one end of the coil plate. Both the coil plate wires and the magnetic field detection element are electrically connected to the digital signal conversion unit.

4. The coin recognition and detection system based on three-coil multi-band detection according to claim 1, characterized in that, The eddy current sensor control unit consists of an interface circuit and a switching circuit connected in sequence. The interface circuit is connected to the eddy current sensor, and the switching circuit is connected to the main control unit. The switching circuit performs on and off operations according to the control signal of the main control unit to control the operating frequency of the eddy current sensor.

5. A coin recognition and detection system based on three-coil multi-band detection according to claim 1, characterized in that, The signal conditioning unit includes a signal amplification circuit and a parameter adjustment circuit, wherein... The parameter adjustment circuit is used to receive control signals from the main control unit to set the amplification factor of the signal amplification circuit; The signal amplification circuit is connected to the receiving coil of the eddy current sensor and the AD peripheral of the main control unit, respectively. It is used to filter, amplify and shape the output signal of the eddy current sensor to the set range according to the control signal received by the parameter adjustment circuit.

6. The coin recognition and detection system based on three-coil multi-band detection according to claim 1, characterized in that, The digital signal conversion unit includes an inductive digital sensor U4 and its peripheral circuitry. The clock signal pin SCLK, chip select signal pin CSB, and data input / output pins SDI and SDO of the U4 are all connected to the main control unit via an SPI interface for transmitting impedance data. The interrupt output pin INTB of the U4 is connected to the external I / O port of the main control unit with interrupt functionality via a resistor R10, enabling the main control unit to distinguish the material of different coins based on the time difference between the rising edge at the start of the conversion and the falling edge at the end of the conversion.

7. A coin recognition and detection method based on three-coil multi-band detection, characterized in that, Includes the following steps: The eddy current sensor control unit controls the operating frequency of the eddy current sensor through interface circuits and switching circuits based on the control signals from the main control unit. The signal conditioning unit filters, amplifies, and shapes the output signal of the eddy current sensor, conditioning its peak value to the range of 2.5V to 3.2V. The signal conditioning unit samples the conditioned signal according to the sampling frequency output by the main control unit and transmits the sampled signal to the main control unit. The main control unit controls the digital signal conversion unit to start, causing the inductive impedance sensor to generate a magnetic field of a specific frequency, and converts the magnetic field change caused by the passing of the coin into digital quantities of eddy loss and inductance, which are then transmitted to the main control unit. The main control unit uses data sampled by the eddy current sensor, as well as eddy loss and inductance data, to determine the face value and authenticity of the coin.

8. The coin recognition and detection method based on three-coil multi-band detection according to claim 7, characterized in that, The process of converting the sensed magnetic field change caused by the passing of the coin into digital quantities of eddy loss and inductance is specifically as follows: When a coin approaches the inductive impedance sensor unit, the digital signal conversion unit starts the conversion, and the interrupt output pin INTB changes from low to high. After the CPU pin of the main control unit detects the level change, it starts recording the current time, which is t1. When the conversion is completed, the interrupt output pin INTB changes from high to low, and the CPU pin of the main control unit detects the level change and starts recording the current time, which is t2. This time is used to characterize the different inductive impedance caused by different coins arriving at the magnetic field. The conversion time t = t2 - t1 is calculated, and t is used as the inductive impedance value.

9. A coin recognition and detection method based on three-coil multi-band detection according to claim 7, characterized in that, The main control unit determines the denomination and authenticity of the coin by sampling data from the eddy current sensor and data on eddy current loss and inductance. Specifically: The data characteristics of the eddy current sensor sampling data, as well as the eddy current loss and inductance data, are compared with the characteristics in the genuine coin feature database to determine the face value and authenticity of the coin to be detected.

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