Abstract:
The present invention discloses a stud sensor, which is used for detecting the object hidden behind a surface, including a first capacitor plate, a second capacitor plate, a first detection circuit coupled to the first capacitor plate, a second detection circuit coupled to the second capacitor plate and a micro control unit. The first detection circuit processes the voltage signal corresponding to the first capacitance of the first capacitor plate and outputs a first voltage signal to the micro control unit. The second detection circuit processes the voltage signal corresponding to the second capacitance of the second capacitor plate and outputs a second voltage signal to the micro control unit. The micro control unit compares the first voltage signal and the second voltage signal to determine the position information including the central position of the object. The stud sensor of the invention also includes an output module to show the position information of the object, an input module to input instructions to the micro control unit. The invention has the properties of small size, high integration, fast response speed, high precision and good anti-interference.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a sensor and, particularly, relates to a stud sensor. 
       DESCRIPTION OF THE PRIOR ART 
       [0002]    Generally, the sensor used for detecting objects hidden behind a surface, for example, objects such as wood, metal and other materials inside a wall, is referred to as a stud sensor. In construction and decoration field, the stud sensor is a very useful tool, which can detect hidden objects, so as to assist the user to locate them to proceed with the subsequent operations, for example, uprooting the iron nails left in a wall, drilling holes on a wall, etc. 
         [0003]    Currently, the common stud sensors are mostly capacitance-based electronic devices, that is because most objects hidden behind a surface have a permittivity different from that of the surrounding substances, thus the hidden objects can be detected as long as the changes of the permittivity can be detected. Normally, the stud sensor has a detection face for coming close to the surface to be detected, and the detection face is arranged with one or more capacitor plates thereon. In use, the detection face reaches close to the surface (such as a wall surface) to be detected, and moves over the surface. When the stud sensor detects a change in the capacitance value of the capacitor plates, it can be determined that there is a hidden object behind the surface at this location. An advanced stud sensor can also determine the boundary, center, material and so fourth of the hidden object. 
         [0004]    With the development of science and technology, the development trend of various electronic devices has been toward being small in size, highly integrated and fast in response speed, and producing a stud sensor with small size, high integration and fast response speed is an object for those skilled in the field, and, also, a stud sensor with smaller size, higher integration and faster response speed can better satisfy the requirement of the user. 
         [0005]    Accordingly, people skilled in the field have been endeavoring in developing a stud sensor, which can realize small size, high integration and fast response speed. 
       SUMMARY OF THE INVENTION 
       [0006]    In view of the above defects in the prior art, the technical problem to solved by the invention is to provide a stud sensor, realizing small size, high integration and fast response speed by using integrated circuit chip. 
         [0007]    In order to achieve the above object, the invention provides a stud sensor, used for detecting an object hidden behind a surface, a detection face of the stud sensor moves along the surface, characterized in that,
       the stud sensor comprises a first capacitor plate, a second capacitor plate, a first detection circuit, a second detection circuit and a micro control unit;   the first capacitor plate and the second capacitor plate are distributed on the detection face; the first capacitor plate and the surface forming a first capacitor having a first capacitance; the second capacitor plate and the surface forming a second capacitor having a second capacitance;   the first detection circuit is coupled to the first capacitor plate, the first detection circuit processes the electrical signal corresponding to the first capacitance and outputs a first voltage signal;   the second detection circuit is coupled to the second capacitor plate, the second detection circuit processes the electrical signal corresponding to the second capacitance and outputs a second voltage signal;   an output end of the first detection circuit is connected to a first input end of the micro control unit, an output end of the second detection is connected to a second input end of the micro control unit; the micro control unit compares the first voltage signal and the second voltage signal, and determines the position of the object according to the result of the comparison.       
 
         [0013]    Further, the micro control unit is an AD micro control unit. 
         [0014]    Further, the first capacitor plate and the second capacitor plate have identical structural parameters and permittivity. 
         [0015]    Further, on the detection face, the first capacitor plate and the second capacitor plate are arranged in parallel. 
         [0016]    Further, each element and connections between each element in the first detection circuit and the second detection circuit are all identical. 
         [0017]    Further, the micro control unit determines the central position of the object when the first voltage signal and the second voltage signal are equal. 
         [0018]    Further, the first detection circuit comprises a first oscillator, the second detection circuit comprises a second oscillator, an input end of the first oscillator connected to a first PWM channel of the micro control unit, an input end of the second oscillator connected to a second PWM channel. 
         [0019]    Further, the first oscillator and the second oscillator are both RC oscillators. 
         [0020]    Further, an output end of the first oscillator is connected to the first capacitor plate, an output end of the second oscillator is connected to the second capacitor plate. 
         [0021]    Further, the first detection circuit includes a first flip-flop, the output end of the first oscillator connected to a first input end of the first flip-flop; the second detection circuit comprises a second flip-flop, the output end of the second oscillator connected to a first input end of the second flip-flop. 
         [0022]    Further, the first flip-flop and the second flip-flop are both CD4093 flip-flops. 
         [0023]    Further, the stud sensor also comprises a power supply module which is respectively connected to the micro control unit, the first detection circuit and the second detection circuit so as to supply power. 
         [0024]    Further, the power supply module comprises a power supply and a regulated power supply chip, the power supply connected to an input end of the regulated power supply chip, an output end of the regulated power supply chip respectively connected to the micro control unit, the first detection circuit and the second detection circuit. 
         [0025]    Further, the power supply module has an indicator light. 
         [0026]    Further, the power supply is a battery pack. 
         [0027]    Further, the stud sensor further comprises an output module, an input end of the output module connected to an output end of the micro control unit. 
         [0028]    Further, the output module is a display. 
         [0029]    Further, the stud sensor further comprises an input module, an output end of the input module connected to a third input end of the micro control unit. 
         [0030]    Further, the input module is a keyboard. 
         [0031]    In a preferred embodiment of the invention, a stud sensor is provided for detecting an object hidden behind a surface, the detection face of which is arranged in parallel with a first capacitor plate and a second capacitor plate with identical structural parameters and permittivity. The first and second capacitor plates respectively form a first capacitor and a second capacitor in relation to the surface (and the object behind it) to be detected. The first and second capacitors have a first and a second capacitance, respectively. The stud sensor also includes a micro control unit, a first detection circuit, a second detection circuit, a power supply module, an output module and an input module. The first and second detection circuits respectively include a first oscillator and a second oscillator respectively connected to the first capacitor plate and the second capacitor plate. The first and second detection circuits also include a plurality of CD4093 flip-flops. The first and second detection circuits respectively implement processes of denoising and amplification to the electrical signals corresponding to the first and second capacitances then acquire a first voltage signal and a second voltage signal. The micro control unit compares the first and second voltage signals, acquires the position information of the object and displays the position information on the output module, the output module being a liquid crystal display. The input module is a keyboard, used for inputting instructions to the micro control unit by the user. The power supply module supplies power to the micro control unit, the first and second detection circuits respectively. It can thus be seen that the stud sensor of the present invention greatly enhances the integration level and response speed of the device by using the micro control unit, and greatly enhances the precision and anti-interference capability by using the first and second detection circuits with oscillators and CD4093 flip-flops and the acquired first and second voltage signals, so the stud sensor is enabled to have properties of small size, high integration, fast response speed, high precision and good anti-interference. 
         [0032]    Referencing now to the figures, the conception, detailed structure and induced technical effect of the present invention will be further expounded for a full understanding of the purpose, characterizations and effects of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]      FIG. 1  is a structural view of the module of the stud sensor in a preferred embodiment of the invention; 
           [0034]      FIG. 2  shows the arrangement of the two capacitor plates of the stud sensor on the detection face, in a preferred embodiment of the invention; 
           [0035]      FIG. 3  shows the circuit structure of the first detection circuit of the stud sensor in a preferred embodiment of the invention; 
           [0036]      FIG. 4  shows the circuit structure of the second detection circuit of the stud sensor in a preferred embodiment of the invention; and 
           [0037]      FIG. 5  shows the circuit structure of the power supply module of the stud sensor in a preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    The stud sensor of the invention is used for detecting an object hidden behind a surface, which has a detection face  20  ( FIG. 2 ). In use, the detection face  20  is attached to or put close to the surface to be detected and moves along the surface. 
         [0039]    As shown in  FIG. 1 , in a preferred embodiment, the stud sensor of the invention includes a micro control unit  10 , a first capacitor plate  21 , a second capacitor plate  22 , a first detection circuit  31 , a second detection circuit  32  and a power supply module  40 . The first capacitor plate  21  and the second capacitor plate  22  have identical structural parameters and permittivity, as shown in  FIG. 2 , and they are arranged in parallel on the detection face  20 . When the detection face  20  is attached to or put close to the surface to be detected, the first capacitor plate  21  and the second capacitor plate  22  respectively form a first capacitor and a second capacitor in relation to the surface (and the object behind it) to be detected. The first capacitor has a first capacitance. The second capacitor has a second capacitance. The micro control unit  10  is an AD micro control unit. 
         [0040]    As shown in  FIG. 3 , the first detection circuit  31  has an input end IN  1  and an output end OUT  1 , wherein the input end IN  1  is connected to the first capacitor plate  21 . The output end OUT  1  is connected to a first input end of the micro control unit  10 . The first detection circuit  31  includes a first oscillator  51 , the input end of the first oscillator  51  is connected to the first PWM channel PWM  1  of the micro control unit  10 , and the output end of the first oscillator  51  is connected to the first capacitor plate  21 . The first detection circuit  31  also includes a first flip-flop U 21 , the first flip-flop U 21  is a CD4093 flip-flop, and the output of the first oscillator  51  is connected to a first input end of the first flip-flop U 21 . 
         [0041]    In this embodiment, the first oscillator  51  consists of resistors R 50 , R 51 , R 52  and capacitors C 21 , C 22 , in which, the resistors R 50 , R 51  and R 52  are connected in series. One end of the capacitor C 21  is connected between the resistor R 50  and the resistor R 51 , and the other end is grounded. One end of the capacitor C 22  is connected between the resistor R 51  and the resistor R 52 , and the other end is grounded. Preferably, the selected resistance value of the resistance R 50 , R 51  and R 52  are respectively 1 KΩ, 1 KΩ and 820 KΩ. The capacitances of the selected capacitors C 21  and C 22  are both 104 μF. The first oscillator  51  outputs a voltage signal having a first oscillation frequency. 
         [0042]    In this embodiment, the first detection circuit  31  also includes the following elements: flip-flop U 22 , flip-flop U 23 , flip-flop U 24 , amplifier U 43 , transistor Q 5 , resistors R 26 , R 53 , R 54 , R 27 , R 30 , R 55 , R 56 , R 31 , R 58 , R 57  and R 34 , capacitors C 24 , C 23 , C 25 , C 26 , C 27 , C 28  and C 29 , and diode D 3 . The connection relationship of these elements is shown in  FIG. 3 , which is not repeated herein. Preferably, the parameters of each of the selected elements are as follows:
       Flip-flop U 22 , flip-flop U 23  and flip-flop U 24  are all CD4093 flip-flops;   The model of amplifier U 43  is LM324;   The model of diode D 3  is IN4148;   Transistor Q 5  is a transistor 9014;   The resistance values of resistors R 26 , R 53 , R 54 , R 27 , R 30 , R 55 , R 56 , R 31 , R 58 , R 57  and R 34  are respectively 120 KΩ, 33 KΩ, 10 KΩ, 47 KΩ, 10 KΩ, 10 KΩ, 470 KΩ, 100 KΩ, 470 KΩ, 150 KΩ and 1 KΩ;   The capacitance values of capacitors C 24 , C 23 , C 25 , C 26 , C 27 , C 28  and C 29  are respectively 471 μF, 104 μF, 471 μF, 471 μF, 105 μF, 103 μF and 104 μF.       
 
         [0049]    As shown in  FIG. 4 , the second detection circuit  32  has an input end IN  2  and the output end OUT  2 , in which the input end IN  2  is connected to the second capacitor plate  22 , the output end OUT  2  is connected to a second input end of the micro control unit  10 . The second detection circuit  32  includes a second oscillator  52 , and the input end of the second oscillator  52  is connected to the second PWM channel PWM  2  of the micro control unit  10 , the output end of the second oscillator  52  is connected to the second capacitor plate  22 . The second detection circuit  32  also includes a second flip-flop U 212 , and the second flip-flop U 212  is a CD4093 flip-flop. The output end of the second oscillator  52  is connected to the first input end of the second flip-flop U 212 . 
         [0050]    In the present embodiment, the second oscillator  52  consists of resistors R 502 , R 512 , R 522  and capacitors C 212 , C 222 , in which, the resistors R 502 , R 512  and R 522  are in series. One end of the capacitor C 212  is connected between the resistor R 502  and the resistor R 512 , and the other end is grounded. One end of the capacitor C 222  is connected between the resistor R 512  and the resistor R 522 , and the other end is grounded. Preferably, the resistance values of the selected resistances R 502 , R 512  and R 522  are respectively 1 KΩ, 1 KΩ and 820 KΩ. The capacitance values of the selected capacitors C 212  and C 222  are both 104 μF. The second oscillator  52  outputs a voltage signal having a second oscillation frequency, and in this embodiment the second oscillation frequency is equal to the first oscillation frequency. 
         [0051]    In this embodiment, the second detection circuit  32  also includes the following elements: flip-flop U 222 , flip-flop U 232 , flip-flop U 242 , amplifier U 432 , transistor Q 52 , resistors R 262 , R 532 , R 542 , R 272 , R 302 , R 552 , R 562 , R 312 , R 582 , R 572  and R 342 , capacitors C 242 , C 232 , C 252 , C 262 , C 272 , C 282  and C 292 , and a diode D 32 . The connection relationship of these elements is shown in  FIG. 4 , and is not repeated herein. Preferably, the parameters of each of the selected elements are as follows:
       Flip-flop U 222 , flip-flop U 232  and flip-flop U 242  are all CD4093 flip-flops;   The model of amplifier U 432  is LM324;   The model of diode D 32  is IN4148;   The transistor Q 52  is a transistor 9014;   The resistance values of resistors R 262 , R 532 , R 542 , R 272 , R 302 , R 552 , R 562 , R 312 , R 582 , R 572  and R 342  are respectively 120 KΩ, 33 KΩ, 10 KΩ, 47 KΩ, 10 KΩ, 10 KΩ, 470 KΩ, 100 KΩ, 470 KΩ, 150 KΩ and 1 KΩ;   The capacitance values of capacitors C 242 , C 232 , C 252 , C 262 , C 272 , C 282  and C 292  are respectively 471 μF, 104 μF, 471 μF, 471 μF, 105 μF, 103 μF and 104 μF.       
 
         [0058]    The power supply module  40  is connected to the micro control unit  10 , the first detection circuit  31  and the second detection circuit  32  respectively so as to supply power to them. As shown in  FIG. 5 , in this embodiment, the power supply module includes a power supply  41 , a regulated power supply chip  42 , a capacitor  43 , a resistor  44  and a light emitting diode  45 , in which, the power supply  41  is a battery pack, the positive pole of which is connected to the input end VIN of the regulated power supply chip  42 , and the negative pole of which is grounded. The output end VOUT of the regulated power supply chip  42  is connected to pin VCC of the micro control unit  10  so as to supply power to the micro control unit  10 , and the ground end of the regulated power supply chip  42  is grounded. The resistor  44  and the light-emitting diode  43  are in series and then in parallel with the capacitor  42 , connected between the output end VOUT and ground. Further, by connecting the first detection circuit  31  and the second detection circuit  32  to the micro control unit pin VCC  10 , a simultaneous power supply to the first detection circuit  31  and the second detection circuit  32  from the power supply module  40  can be achieved, the specific connection mode are shown as in  FIGS. 3 and 4 . The parameters and models of the selected resistor  44  and capacitor  43  can be determined according to actual requirement. 
         [0059]    Thus, the changes of the first capacitance will affect the oscillation frequency of the voltage signal from the first oscillator  51  received by the first flip-flop U 21  of the first detection circuit  31 , and the other circuit portion of the first detection circuit  31  outputs a first voltage signal to the micro control unit  10  after implementing processes such as denoising, amplification to the voltage signal. In the same manner, the changes of the second capacitance will affect the oscillation frequency of the voltage signal from the second oscillator  52  received by the second flip-flop U 212  of the second detection circuit  32 , and the other circuit portion of the second detection circuit  32  outputs a second voltage signal to the micro control unit  10  after implementing processes such as denoising, amplification to the voltage signal. The micro control unit  10  compares the first voltage signal and the second voltage signal to obtain the position information of the object (including the central position of the object, for example, when the first voltage signal and the second voltage signal are equal, i.e., when both of which have the same amplitude and oscillation frequency, the location of the central position of the first capacitor plate  21  and the second capacitor plates  22  of the stud sensor at the time is determined to be the central position of object hidden behind the surface to be detected). 
         [0060]    The stud sensor of the invention also includes an output module  60  connected at an output end of the micro control unit  10  used for displaying the position information of the hidden object obtained by the micro control unit  10 . The output module  60  can be a display, such as a liquid crystal display, showing the position information of the object in text or image, and it can also be a loudspeaker sending the position information of the object in the form of sound, and further, it can also include both a display and a loudspeaker. 
         [0061]    The stud sensor of the invention also includes an input module  70  connected at the third input end of the micro control unit  10  used for allowing the user to input instructions to the micro control unit  10 , such as adjusting the oscillation frequency of the electrical signal output by PWM channels PWM  1  and PWM  2  of the micro control unit  10 . The input module  70  in the present embodiment is a keyboard, including an entitative keyboard or a virtual keyboard formed on a liquid crystal display. 
         [0062]    The foregoing described the preferred embodiments of the present invention. It should be understood that an ordinary one skilled in the art can make many modifications and variations according to the concept of the present invention without creative work. Therefore, any person skilled in the art can get any technical solution through logical analyses, deductions and limited experiments, which should fall in the protection scope defined by the claims.