CN112749775B - Paper counting assembly based on measure electric capacity - Google Patents
Paper counting assembly based on measure electric capacity Download PDFInfo
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- CN112749775B CN112749775B CN202011510298.2A CN202011510298A CN112749775B CN 112749775 B CN112749775 B CN 112749775B CN 202011510298 A CN202011510298 A CN 202011510298A CN 112749775 B CN112749775 B CN 112749775B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06M—COUNTING MECHANISMS; COUNTING OF OBJECTS NOT OTHERWISE PROVIDED FOR
- G06M7/00—Counting of objects carried by a conveyor
- G06M7/02—Counting of objects carried by a conveyor wherein objects ahead of the sensing element are separated to produce a distinct gap between successive objects
- G06M7/06—Counting of flat articles, e.g. of sheets of paper
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
Abstract
The invention discloses a paper counting device based on a measuring capacitor, which comprises an STM32 control module, a paper capacitor plate module, an effective value amplification module, a power supply module, a liquid crystal display module and a key. The liquid crystal display module and the keys are connected with the STM32 control module, the STM32 control module is connected with the effective value amplification module through an AD interface, and the effective value amplification module is connected with the paper capacitor plate module; and the power supply module is connected with the STM32 control module and the effective value amplification module and supplies power to the STM32 control module and the effective value amplification module. The invention can freely switch two working modes of self calibration and formal measurement by setting the key; the invention has the advantages of low design cost, low power loss, high sensitivity, high resolution, strong reliability, strong anti-electromagnetic interference capability, wide application range and good practical value.
Description
Technical Field
The invention relates to the technical field of paper counting, in particular to a paper counting device based on a measuring capacitor.
Technical Field
The paper counting is widely applied in life and industrial production, and the working efficiency can be greatly improved by using a machine to replace manpower. The paper counting device has a plurality of difficulties, firstly, the requirement on a measuring circuit is high because the thickness of the paper is extremely small; secondly, the paper counting device is easily interfered by external environment, such as the interference of human body approaching to the capacitance signal; again, the freshness of the paper may cause its thickness to vary and thus cause errors in the measurement results.
Disclosure of Invention
The invention provides a paper counting device based on a measuring capacitor. The method can accurately and quickly measure and display the number of the paper sheets.
The technical scheme of the invention is realized as follows:
the utility model provides a paper counting assembly based on measure electric capacity, includes STM32 control module, paper electric capacity polar plate module, effective value amplification module, power module, liquid crystal display module and button.
The liquid crystal display module and the keys are connected with the STM32 control module, the STM32 control module is connected with the effective value amplification module through an AD interface, and the effective value amplification module is connected with the paper capacitor plate module; and the power supply module is connected with the STM32 control module and the effective value amplification module and supplies power to the STM32 control module and the effective value amplification module.
The paper capacitor plate module comprises a first metal plate, a second metal plate, a divider resistor R and a sine input excitation signal. The sine input excitation signal is generated by an STM32 control module; a sine input excitation signal and a divider resistor R, a first metal polar plate and a second metal polar plate form a series circuit. Simultaneously, first metal polar plate and second metal polar plate are connected with the virtual value respectively and enlarge the module, are used for placing the volume of awaiting measuring paper between first metal polar plate and the second metal polar plate, and first metal polar plate and second metal polar plate use adjustable device to fix.
The adjustable device comprises four steel shafts, an upper pressing plate and a lower pressing plate, wherein the lower pressing plate and the upper pressing plate are arranged in parallel, the steel shafts are arranged at four corners of the upper pressing plate and the lower pressing plate, the lower pressing plate is fixedly connected with the steel shafts, an oil-containing bearing is arranged at the joint of the upper pressing plate and the steel shafts to keep smooth degree, the lower pressing plate and the upper pressing plate are constantly in a horizontal position through the steel shafts, the first metal polar plate and the second metal polar plate are respectively fixed on the upper surface of the lower pressing plate and the lower surface of the upper pressing plate, and the distance between the steel shafts is larger than the length of paper to be tested.
The effective value amplification module comprises a voltage follower Q1A, a voltage division resistor R1, an RC filter resistor R2, a voltage division resistor R3, an amplification resistor R4, an amplification resistor R5, an amplification resistor R6, a current limiting resistor R7, a current limiting resistor R8, an AD736 effective value conversion module, a decoupling capacitor C1, a DC blocking capacitor C2, a DC blocking capacitor C3, a decoupling capacitor C4, a filter capacitor C5, a filter capacitor C6, a filter capacitor C7, an RC filter capacitor C8, a filter capacitor C9, a filter capacitor C10, a filter capacitor C11, a filter capacitor C12 and a voltage amplifier Q2B.
A pin 1 of the voltage follower Q1A is connected with a pin 2 of the voltage follower Q1 and one end of a voltage dividing resistor R1, a pin 3 of the voltage follower Q1A is connected with one end of a DC blocking capacitor C2, the other end of a DC blocking capacitor C2 is connected with CIN, the other end of the voltage dividing resistor R1 is connected with one end of a voltage dividing resistor R3 and one end of a DC blocking capacitor C3, and the other end of the DC blocking capacitor C3 is connected with a pin 2 of an AD736 effective value conversion module. A pin 1 of the AD736 effective value conversion module is connected with one end of a decoupling capacitor C1, and a pin 8 of the AD736 effective value conversion module is connected with the other end of the decoupling capacitor C1 and AGND; the 4 pins of the AD736 effective value conversion module are connected with one ends of a filter capacitor C6, a filter capacitor C7 and a filter capacitor C8, and the other ends of the filter capacitor C6, the filter capacitor C7 and the filter capacitor C8 are connected with the 5 pins of the AD736 effective value conversion module; a pin 5 of the voltage amplifier Q2B is connected with a pin 6 of the AD736 effective value conversion module and one end of a decoupling capacitor C4, the other end of the decoupling capacitor C4 is connected with a pin 3 of the AD736 effective value conversion module, the pin 6 of the voltage amplifier Q2B is connected with one end of an amplification resistor R4 and one end of an amplification resistor R5, the other end of the amplification resistor R4 is connected with AGND, the other end of the amplification resistor R5 is connected with one end of the amplification resistor R6, a pin 7 of the voltage amplifier Q2B is connected with the other end of the amplification resistor R6 and one end of an RC filter resistor R2, and the other end of the RC filter resistor R2 and one end of an RC filter capacitor C8 are connected with ADCIN. The other end of the RC filter capacitor C8 is connected with AGND;
-5V and 5V are directly provided by external equipment, -5V is connected with one end of a current limiting resistor R7, the other end of the current limiting resistor R7 is connected with one end of a filter capacitor C9 and one end of a filter capacitor C10, and the other end of the filter capacitor C9 and the other end of the filter capacitor C10 are connected with AGND, so as to obtain-VS 3; the voltage of 5V is connected with one end of a current-limiting resistor R8, the other end of the current-limiting resistor R8 is connected with one end of a filter capacitor C11 and one end of a filter capacitor C12, and the other end of the filter capacitor C11 and the other end of the filter capacitor C12 are connected with AGND, so that + VS3 is obtained.
The liquid crystal display module adopts an LCD (liquid crystal display) screen for man-machine interaction and displaying the number of the measured paper.
The keys are used for man-machine interaction and sending instructions to the controller.
The capacitance C between the first metal polar plate and the second metal polar plate is as follows:
wherein epsilon is dielectric permittivity (relative permittivity), delta is absolute permittivity in vacuum, delta is 8.86 XF/m, k is electrostatic force constant, k is 8.9880X 10, unit is Nm/C (Newton-meter 2/Coulomb 2), S is opposite area of the two polar plates, and d is vertical distance between the two polar plates.
Since epsilon, delta, and S are known parameters, the capacitance C between the first metal plate and the second metal plate is only related to the vertical distance d between the plates. The larger d is, the smaller the capacitance C between the first metal plate and the second metal plate is; the smaller d, the larger the capacitance C between the first metal plate and the second metal plate.
Capacitive reactance between two metal polar plates
And the voltage dividing resistor R is connected in series, sine input excitation signals Asinwt are supplied to two ends of the voltage dividing resistor R, and the vertical distance d between two polar plates is converted into an alternating current signal with a corresponding relation according to ohm's theorem.
The capacitance C represents the capacitance between the first metal plate and the second metal plate, and its capacitive reactance is
It is connected in series with a resistor R and a sinusoidal input excitation signal V, V ═ Asinwt is switched in. Cin represents a voltage across the capacitor C, and this signal is input to the effective value amplification circuit. From circuit knowledge, Cin ═ Z (V/(R + Z)) ×. Since V and R are definite, the capacitive reactance Z is related to the capacitance C, and the capacitance C is related to the distance d between the first metal plate and the second metal plate, so the larger the distance d between the first metal plate and the second metal plate is, the larger Cin is; the smaller the distance d between the first metal plate and the second metal plate is, the smaller Cin is.
The STM32 control module adopts STM32F103RCT6 singlechip.
A method for using a paper counting device based on capacitance measurement comprises the following steps:
step (1), establishing a candidate data table, and inputting the candidate data table to an STM32 control module;
measuring and recording AD values (a0-aN) corresponding to N sheets from 0 through a sheet counting device under different environments to obtain M candidate data tables under different environments; and inputting the obtained M candidate data tables under different environments into an STM32 control module for storage.
And (2) after the acquisition of the M candidate data tables is completed, performing a self-correction algorithm according to the M candidate data tables, and selecting the candidate data table with the minimum error as a paper counting data table.
The paper counting device is used for collecting AD values of K times of different numbers of paper to be tested, then calculating errors of the M candidate data tables respectively through an error formula, and finding the candidate data table with the smallest error with the AD value obtained through measurement; and taking the candidate data table with the minimum error as a paper counting data table for subsequent measurement of the paper.
The error E is calculated by the following formula, i represents the ith candidate data table, j represents j sheets of paper, b [ j ] represents the AD value of the actually measured j sheets of paper, and ai [ j ] represents the jth numerical value of the ith candidate data table.
Step (3), putting paper to be measured into a measurement space of a paper capacitor plate module, detecting the capacitance value between the first metal plate and the second metal plate in real time through an effective value amplification module, and converting the capacitance value into an AD effective value;
step (4), the STM32 control module reads AD effective value data of the effective value amplification module through an ADC (analog-to-digital converter) of the STM32 control module, and compares the AD effective value data with a preset value interval in a candidate data table to determine the number of paper sheets;
and (5) pressing a key of the paper counting device, sending a paper measuring result to the liquid crystal display module by the STM32 control module, and displaying the number of the paper to be measured by the liquid crystal display module.
The invention has the beneficial effects that:
the invention can freely switch two working modes of self calibration and formal measurement by setting the key; the invention has the advantages of low design cost, low power loss, high sensitivity, high resolution, strong reliability, strong anti-electromagnetic interference capability, wide application range and good practical value.
Drawings
FIG. 1 is a block diagram of a sheet counting apparatus;
FIG. 2 is a circuit diagram of a paper capacitor plate module according to an embodiment of the present invention;
FIG. 3 is a circuit diagram of a valid value amplification module according to an embodiment of the present invention;
FIG. 4 is a general flow diagram of an embodiment of the present invention;
FIG. 5 is a flowchart of a DAC subroutine according to an embodiment of the present invention;
FIG. 6 is a flowchart of an ADC subroutine according to an embodiment of the present invention.
Detailed Description
The objects and effects of the present invention will become more apparent from the following detailed description of the present invention with reference to the accompanying drawings.
As shown in FIG. 1, the device comprises an STM32 control module, a paper capacitor plate module, an effective value amplification module, a power supply module, a liquid crystal display module and keys. The liquid crystal display module and the keys are connected with the STM32 control module, the STM32 control module is connected with the effective value amplification module through an AD interface, and the effective value amplification module is connected with the paper capacitor plate module; and the STM32 control module and the effective value amplification module are connected with the power supply module. The output of the power supply module is 5V voltage. The STM32 control module adopts STM32F103RCT6 of STM company, the singlechip dominant frequency is up to 72Mhz, 64 pins are provided, and abundant functional modules such as an AD module and a DA module are integrated, so that the requirements of the invention are met. The effective value amplifying circuit adopts an AD736 effective value conversion chip, and the AD736 is a single-chip precise true effective value AC/DC converter subjected to laser correction. The method is mainly characterized by high accuracy, good sensitivity, fast measurement speed, good frequency characteristic (the working frequency range can reach 0-460 kHz), high input impedance, low output impedance, wide power supply range, low power consumption and the maximum power supply working current of 200 muA, and the comprehensive error of measuring sine wave voltage by using the method is not more than +/-3 percent. The effective value circuit is simple to implement, the pressure of a follow-up program is relieved, and the maximum efficiency is realized on STM32F103 limited hardware resources.
The utility model provides a paper counting assembly based on measure electric capacity, includes STM32 control module, paper electric capacity polar plate module, effective value amplification module, power module, liquid crystal display module and button.
The liquid crystal display module and the keys are connected with the STM32 control module, the STM32 control module is connected with the effective value amplification module through an AD interface, and the effective value amplification module is connected with the paper capacitor plate module; and the power supply module is connected with the STM32 control module and the effective value amplification module and supplies power to the STM32 control module and the effective value amplification module.
The paper capacitor plate module comprises a first metal plate, a second metal plate, a divider resistor R and a sine input excitation signal. The sine input excitation signal is generated by an STM32 control module; a sine input excitation signal and a divider resistor R, a first metal polar plate and a second metal polar plate form a series circuit. Meanwhile, the first metal pole plate and the second metal pole plate are respectively connected with an effective value amplification module, paper to be measured is placed between the first metal pole plate and the second metal pole plate, and the first metal pole plate and the second metal pole plate are fixed through an adjustable device.
The adjustable device comprises four steel shafts, an upper pressing plate and a lower pressing plate, wherein the lower pressing plate and the upper pressing plate are arranged in parallel, the steel shafts are arranged at four corners of the upper pressing plate and the lower pressing plate, the lower pressing plate is fixedly connected with the steel shafts, an oil-containing bearing is arranged at the joint of the upper pressing plate and the steel shafts to keep smooth degree, the lower pressing plate and the upper pressing plate are constantly in a horizontal position through the steel shafts, the first metal polar plate and the second metal polar plate are respectively fixed on the upper surface of the lower pressing plate and the lower surface of the upper pressing plate, and the distance between the steel shafts is larger than the length of paper to be tested.
As shown in fig. 3, the effective value amplifying module includes a voltage follower Q1A, a voltage dividing resistor R1, an RC filter resistor R2, a voltage dividing resistor R3, an amplification factor resistor R4, an amplification factor resistor R5, an amplification factor resistor R6, a current limiting resistor R7, a current limiting resistor R8, an AD736 effective value converting module, a decoupling capacitor C1, a dc blocking capacitor C2, a dc blocking capacitor C3, a decoupling capacitor C4, a filter capacitor C5, a filter capacitor C6, a filter capacitor C7, an RC filter capacitor C8, a filter capacitor C9, a filter capacitor C10, a filter capacitor C11, a filter capacitor C12, and a voltage amplifier Q2B.
A pin 1 of the voltage follower Q1A is connected with a pin 2 of the voltage follower Q1 and one end of a voltage dividing resistor R1, a pin 3 of the voltage follower Q1A is connected with one end of a DC blocking capacitor C2, the other end of a DC blocking capacitor C2 is connected with CIN, the other end of the voltage dividing resistor R1 is connected with one end of a voltage dividing resistor R3 and one end of a DC blocking capacitor C3, and the other end of the DC blocking capacitor C3 is connected with a pin 2 of an AD736 effective value conversion module. A pin 1 of the AD736 effective value conversion module is connected with one end of a decoupling capacitor C1, and a pin 8 of the AD736 effective value conversion module is connected with the other end of the decoupling capacitor C1 and AGND; the 4 pins of the AD736 effective value conversion module are connected with one ends of a filter capacitor C6, a filter capacitor C7 and a filter capacitor C8, and the other ends of the filter capacitor C6, the filter capacitor C7 and the filter capacitor C8 are connected with the 5 pins of the AD736 effective value conversion module; a pin 5 of the voltage amplifier Q2B is connected with a pin 6 of the AD736 effective value conversion module and one end of a decoupling capacitor C4, the other end of the decoupling capacitor C4 is connected with a pin 3 of the AD736 effective value conversion module, the pin 6 of the voltage amplifier Q2B is connected with one end of an amplification resistor R4 and one end of an amplification resistor R5, the other end of the amplification resistor R4 is connected with AGND, the other end of the amplification resistor R5 is connected with one end of the amplification resistor R6, a pin 7 of the voltage amplifier Q2B is connected with the other end of the amplification resistor R6 and one end of an RC filter resistor R2, and the other end of the RC filter resistor R2 and one end of an RC filter capacitor C8 are connected with ADCIN. The other end of the RC filter capacitor C8 is connected with AGND;
-5V and 5V are directly provided by external equipment, -5V is connected with one end of a current limiting resistor R7, the other end of the current limiting resistor R7 is connected with one end of a filter capacitor C9 and one end of a filter capacitor C10, and the other end of the filter capacitor C9 and the other end of the filter capacitor C10 are connected with AGND, so as to obtain-VS 3; the voltage of 5V is connected with one end of a current-limiting resistor R8, the other end of the current-limiting resistor R8 is connected with one end of a filter capacitor C11 and one end of a filter capacitor C12, and the other end of the filter capacitor C11 and the other end of the filter capacitor C12 are connected with AGND, so that + VS3 is obtained.
The liquid crystal display module adopts an LCD (liquid crystal display) screen for man-machine interaction and displaying the number of the measured paper.
The keys are used for man-machine interaction and sending instructions to the controller.
The capacitance C between the first metal polar plate and the second metal polar plate is as follows:
wherein epsilon is dielectric permittivity (relative permittivity), delta is absolute permittivity in vacuum, delta is 8.86 XF/m, k is electrostatic force constant, k is 8.9880X 10, unit is Nm/C (Newton-meter 2/Coulomb 2), S is opposite area of the two polar plates, and d is vertical distance between the two polar plates.
Since epsilon, delta, and S are known parameters, the capacitance C between the first metal plate and the second metal plate is only related to the vertical distance d between the plates. The larger d is, the smaller the capacitance C between the first metal plate and the second metal plate is; the smaller d, the larger the capacitance C between the first metal plate and the second metal plate.
Capacitive reactance between two metal polar plates
And the voltage dividing resistor R is connected in series, sine input excitation signals Asinwt are supplied to two ends of the voltage dividing resistor R, and the vertical distance d between two polar plates is converted into an alternating current signal with a corresponding relation according to ohm's theorem.
As shown in FIG. 2, the capacitance C represents the capacitance between the first metal plate and the second metal plate, and its capacitive reactance is
It is connected in series with a resistor R and a sinusoidal input excitation signal V, V ═ Asinwt is switched in. Cin represents a voltage across the capacitor C, and this signal is input to the effective value amplification circuit. From circuit knowledge, Cin ═ (V/(R + Z)) × Z. Since V and R are definite, the capacitive reactance Z is related to the capacitance C, and the capacitance C is related to the distance d between the first metal plate and the second metal plate, so that the first metal plate and the second metal plate are connectedThe larger the distance d between the plates, the larger Cin; the smaller the distance d between the first metal plate and the second metal plate is, the smaller Cin is.
The STM32 control module adopts STM32F103RCT6 singlechip of STM company. The module has 3 ADCs with 12 bits of precision, and each ADC has a maximum of 16 external channels. The ADC1 and the ADC2 both have 16 external channels, and the ADC3 generally has 8 external channels according to the number of different channels of the CPU pins.
A method for using a paper counting device based on capacitance measurement comprises the following steps:
step (1), establishing a candidate data table, and inputting the candidate data table to an STM32 control module;
measuring and recording AD values (a0-aN) corresponding to N sheets from 0 through a sheet counting device under different environments to obtain M candidate data tables under different environments; and inputting the obtained M candidate data tables under different environments into an STM32 control module for storage.
And (2) after the collection of the M candidate data tables is completed, performing a self-correction algorithm according to the M candidate data tables, and selecting the candidate data table with the minimum error as a paper counting data table.
The paper counting device is used for collecting AD values of K times of different numbers of paper to be tested, then calculating errors of the M candidate data tables respectively through an error formula, and finding the candidate data table with the smallest error with the AD value obtained through measurement; and taking the candidate data table with the minimum error as a paper counting data table for subsequent measurement of the paper.
The error E is calculated by the following formula, i represents the ith candidate data table, j represents j paper, bj represents the AD value of the j paper actually measured, and ai [ j ] represents the jth value of the ith candidate data table.
Step (3), placing paper to be measured into a measurement space of a paper capacitor plate module, detecting the capacitance value between the first metal plate and the second metal plate in real time through an effective value amplification module, and converting the capacitance value into an AD effective value;
step (4), the STM32 control module reads AD effective value data of the effective value amplification module through an ADC (analog-to-digital converter) of the STM32 control module, and compares the AD effective value data with a preset value interval in a candidate data table to determine the number of paper sheets;
and (5) pressing a key of the paper counting device, sending the paper measuring result to the liquid crystal display module by the STM32 control module, and displaying the number of the paper to be measured by the liquid crystal display module.
As shown in fig. 3, the present invention designs an acquisition system circuit based on an AD736 effective value conversion chip. Firstly, an input signal passes through a voltage follower after coming in, so that the anti-interference capability of the circuit is improved; secondly, because the input of the AD736 has a certain range, the voltage is divided by the resistors R3 and R6 and then is input into a Vin pin of the AD736 chip; then, after the chip outputs an AD effective value signal, the signal is subjected to signal amplification through OPA 4171; and finally, acquiring the signal by an STM32 control module AD to obtain a corresponding AD value. The working voltage of the AD736 chip and the OPA4171 is + -5V.
The invention designs an STM32 control module circuit which consists of an STM32F103RCT6 circuit, a reset circuit, a key circuit, a download circuit, a 5V to 3.3V circuit, an LCD liquid crystal display circuit, a filter circuit, an LED indicator light circuit and a buzzer circuit. The single chip microcomputer is powered by 3.3V, and the downloading circuit downloads programs in an SWD downloading mode through the downloading circuit; the AMS1117 voltage reduction chip is used for the circuit from 5V to 3.3V; the filter circuit performs filtering by using two capacitors 104 connected in parallel; the buzzer circuit drives the buzzer by using the on-off characteristic of the triode; the LED indicating lamp circuit is connected with a 1K resistor in series to protect the LED lamp.
FIG. 4 is a flow chart of the whole system of the device, which comprises the following steps:
step 1: the controller is powered on, and the charger can be used for supplying power;
and 2, step: the key 1 selects a self-correction mode or a measurement mode, and firstly enters the self-correction mode, wherein the correction method comprises the steps of measuring and recording a plurality of groups of candidate data tables in advance, collecting different paper sheets for 10 times, and selecting one candidate data table with the minimum error as a paper sheet counting data table;
and step 3: after the correction is finished, pressing the key 2 to start the paper counting function, and then prompting the start of counting by the buzzer;
and 4, step 4: as shown in fig. 5, the STM32 single chip microcomputer outputs a 5Khz sine wave excitation signal to the effective value measuring circuit through the DAC and DMA module of the STM 32;
and 5: as shown in fig. 6, after passing through the effective value measurement circuit, the signal is collected by using an ADC and a DMA module of STM 32;
step 6: converting the value acquired by the ADC through data operation, and searching the position in a table obtained by correspondingly correcting the value to obtain the number of paper;
and 7: the result is displayed in the LCD liquid crystal.
Claims (6)
1. A paper counting device based on a measuring capacitor is characterized by comprising an STM32 control module, a paper capacitor plate module, an effective value amplification module, a power supply module, a liquid crystal display module and a key;
the liquid crystal display module and the keys are connected with the STM32 control module, the STM32 control module is connected with the effective value amplification module through an AD interface, and the effective value amplification module is connected with the paper capacitor plate module; the power supply module is connected with the STM32 control module and the effective value amplification module and supplies power to the STM32 control module and the effective value amplification module;
the paper capacitor plate module comprises a first metal plate, a second metal plate, a divider resistor R and a sine input excitation signal; the sine input excitation signal is generated by an STM32 control module; a sinusoidal input excitation signal and a divider resistor R, a first metal polar plate and a second metal polar plate form a series circuit; meanwhile, the first metal pole plate and the second metal pole plate are respectively connected with an effective value amplification module, paper to be measured is placed between the first metal pole plate and the second metal pole plate, and the first metal pole plate and the second metal pole plate are fixed by using an adjustable device;
the effective value amplification module comprises a voltage follower Q1A, a voltage division resistor R1, an RC filter resistor R2, a voltage division resistor R3, an amplification resistor R4, an amplification resistor R5, an amplification resistor R6, a current limiting resistor R7, a current limiting resistor R8, an AD736 effective value conversion module, a decoupling capacitor C1, a DC blocking capacitor C2, a DC blocking capacitor C3, a decoupling capacitor C4, a filter capacitor C5, a filter capacitor C6, a filter capacitor C7, an RC filter capacitor C8, a filter capacitor C9, a filter capacitor C10, a filter capacitor C11, a filter capacitor C12 and a voltage amplifier Q2B;
a pin 1 of the voltage follower Q1A is connected with a pin 2 of the voltage follower Q1 and one end of a divider resistor R1, a pin 3 of the voltage follower Q1A is connected with one end of a dc blocking capacitor C2, the other end of a dc blocking capacitor C2 is connected with CIN, the other end of the divider resistor R1 is connected with one end of a divider resistor R3 and one end of a dc blocking capacitor C3, and the other end of the dc blocking capacitor C3 is connected with a pin 2 of the AD736 effective value conversion module; a pin 1 of the AD736 effective value conversion module is connected with one end of a decoupling capacitor C1, and a pin 8 of the AD736 effective value conversion module is connected with the other end of the decoupling capacitor C1 and AGND; the 4 pins of the AD736 effective value conversion module are connected with one ends of a filter capacitor C6, a filter capacitor C7 and a filter capacitor C8, and the other ends of the filter capacitor C6, the filter capacitor C7 and the filter capacitor C8 are connected with the 5 pins of the AD736 effective value conversion module; a pin 5 of a voltage amplifier Q2B is connected with a pin 6 of an AD736 effective value conversion module and one end of a decoupling capacitor C4, the other end of the decoupling capacitor C4 is connected with a pin 3 of the AD736 effective value conversion module, the pin 6 of the voltage amplifier Q2B is connected with one end of an amplification factor resistor R4 and one end of an amplification factor resistor R5, the other end of the amplification factor resistor R4 is connected with AGND, the other end of the amplification factor resistor R5 is connected with one end of the amplification factor resistor R6, a pin 7 of the voltage amplifier Q2B is connected with the other end of the amplification factor resistor 6 and one end of an RC filter resistor R2, and the other end of the RC filter resistor R2 and one end of an RC filter capacitor C8 are connected with ADCIN; the other end of the RC filter capacitor C8 is connected with AGND;
-5V and 5V are directly provided by external equipment, -5V is connected with one end of a current limiting resistor R7, the other end of the current limiting resistor R7 is connected with one end of a filter capacitor C9 and one end of a filter capacitor C10, and the other end of the filter capacitor C9 and the other end of the filter capacitor C10 are connected with AGND, so as to obtain-VS 3; the voltage of 5V is connected with one end of a current-limiting resistor R8, the other end of the current-limiting resistor R8 is connected with one end of a filter capacitor C11 and one end of a filter capacitor C12, and the other end of the filter capacitor C11 and the other end of the filter capacitor C12 are connected with AGND, so that + VS3 is obtained.
2. The paper counting device based on the measured capacitance as claimed in claim 1, wherein the adjustable device comprises four steel shafts, an upper pressing plate and a lower pressing plate, the lower pressing plate and the upper pressing plate are arranged in parallel, the steel shafts are arranged at four corners of the upper pressing plate and the lower pressing plate, the lower pressing plate is fixedly connected with the steel shafts, oil-containing bearings are arranged at the joints of the upper pressing plate and the steel shafts to keep smooth, the lower pressing plate and the upper pressing plate are constantly in a horizontal position through the steel shafts, the first metal polar plate and the second metal polar plate are respectively fixed on the upper surface of the lower pressing plate and the lower surface of the upper pressing plate, and the distance between the steel shafts is greater than the length of paper to be measured.
3. The paper counting device based on the measured capacitor as claimed in claim 1, wherein the LCD module adopts an LCD for human-computer interaction to display the number of the measured paper.
4. The paper counting device based on the measured capacitance as claimed in claim 2, wherein the capacitance C between the first metal plate and the second metal plate is:
wherein epsilon is dielectric permittivity (relative permittivity), delta is absolute permittivity in vacuum, delta is 8.86 xF/m, k is electrostatic force constant, k is 8.9880 x 10, unit is Nm/C (Newton-meter 2/Coulomb 2), S is opposite area of two polar plates, and d is vertical distance between the two polar plates;
because ε, δ, and S are all known parameters, the capacitance C between the first metal plate and the second metal plate is only related to the vertical distance d between the plates; the larger d is, the smaller the capacitance C between the first metal plate and the second metal plate is; the smaller d is, the larger capacitance C between the first metal plate and the second metal plate is;
capacitive reactance between two metal electrode plates
The voltage divider resistor R is connected in series, sine input excitation signals Asinwt are supplied to two ends of the voltage divider resistor R, and the vertical distance d between two polar plates is converted into an alternating current signal with a corresponding relation according to ohm's theorem;
the capacitance C represents the capacitance between the first metal plate and the second metal plate, and its capacitive reactance is
The sine input excitation signal is connected with a resistor R in series, and a sine input excitation signal V is connected; cin represents a voltage across the capacitor C, which signal is to be input into the effective value amplification circuit; as can be seen from circuit knowledge, Cin ═ (V/(R + Z)) × Z; since V and R are definite, the capacitive reactance Z is related to the capacitance C, and the capacitance C is related to the distance d between the first metal plate and the second metal plate, so the larger the distance d between the first metal plate and the second metal plate is, the larger Cin is; the smaller the distance d between the first metal plate and the second metal plate is, the smaller Cin is.
5. The paper counting device based on the measured capacitor as claimed in claim 1, wherein the STM32 control module adopts STM32F103RCT6 singlechip.
6. A sheet counting device based on capacitance measurement according to any one of claims 1 to 5, characterized in that the use method of the sheet counting device based on capacitance measurement comprises the following steps:
step (1), establishing a candidate data table, and inputting the candidate data table to an STM32 control module;
measuring and recording AD values (a0-aN) corresponding to N sheets from 0 through a sheet counting device under different environments to obtain M candidate data tables under different environments; inputting the obtained M candidate data tables under different environments into an STM32 control module for storage;
step (2), after M candidate data tables are collected, performing a self-correcting algorithm according to the M candidate data tables, and selecting the candidate data table with the minimum error as a paper counting data table;
the paper counting device is used for collecting AD values of K times of different numbers of paper to be tested, then calculating errors of the M candidate data tables respectively through an error formula, and finding the candidate data table with the smallest error with the AD value obtained through measurement; taking the candidate data table with the minimum error as a paper counting data table for subsequent measurement of paper;
calculating an error E by the following formula, wherein i represents the ith candidate data table, j represents j sheets of paper, b [ j ] represents the AD value of the actually measured j sheets of paper, and ai [ j ] represents the jth numerical value of the ith candidate data table;
step (3), putting paper to be measured into a measurement space of a paper capacitor plate module, detecting the capacitance value between the first metal plate and the second metal plate in real time through an effective value amplification module, and converting the capacitance value into an AD effective value;
step (4), the STM32 control module reads AD effective value data of the effective value amplification module through an ADC (analog-to-digital converter) of the STM32 control module, and compares the AD effective value data with a preset value interval in a candidate data table to determine the number of paper sheets;
and (5) pressing a key of the paper counting device, sending the paper measuring result to the liquid crystal display module by the STM32 control module, and displaying the number of the paper to be measured by the liquid crystal display module.
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| US4608704A (en) * | 1982-11-10 | 1986-08-26 | Brandt, Incorporated | Method and apparatus for counting sheets which may be fed in skewed and/or overlapping fashion |
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| CN110991599A (en) * | 2019-12-28 | 2020-04-10 | 中原工学院 | Paper counting display device |
| CN210466456U (en) * | 2019-10-16 | 2020-05-05 | 杭州师范大学钱江学院 | Paper quantity detection device based on capacitive sensor |
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| US4608704A (en) * | 1982-11-10 | 1986-08-26 | Brandt, Incorporated | Method and apparatus for counting sheets which may be fed in skewed and/or overlapping fashion |
| CN2078024U (en) * | 1990-10-25 | 1991-05-29 | 广东省中山市古镇无线电厂 | Monitor device of counting and quality of papers |
| CN203882379U (en) * | 2014-04-10 | 2014-10-15 | 尤新革 | Currency counting and detecting machine with automatic brightness calibration function |
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