阅读说明：本技术 无刷直流电机转速测量装置及其使用方法 (Brushless direct current motor rotating speed measuring device and using method thereof ) 是由 王浩陈 刘圣亚 魏海峰 张懿 李垣江 刘维亭 于 2019-10-16 设计创作，主要内容包括：本发明公开了一种无刷直流电机转速测量装置,包括：接口模块、频率电压转换模块、电压显示模块、转换比例控制模块,接口模块与频率电压转换模块相连,接口模块用于接入无刷直流电机的霍尔传感器信号；频率电压转换模块与电压显示模块相连,频率电压转换模块用将无刷直流电机的霍尔传感器信号转化成线性的电压信号；电压显示模块,基于频率电压转换模块输出的电压信号显示电压值；转换比例控制模块和频率电压转换模块,用于根据无刷直流电机的极对数控制频率电压转换比例。本发明直接利用无刷直流电机中的霍尔传感器带有的转速信息,实现对无刷直流电机转速的实时显示,有效判断无刷直流电机的运行状态。(The invention discloses a brushless DC motor rotating speed measuring device, comprising: the device comprises an interface module, a frequency-voltage conversion module, a voltage display module and a conversion proportion control module, wherein the interface module is connected with the frequency-voltage conversion module and is used for accessing Hall sensor signals of the brushless direct current motor; the frequency-voltage conversion module is connected with the voltage display module and is used for converting a Hall sensor signal of the brushless direct current motor into a linear voltage signal; the voltage display module displays a voltage value based on the voltage signal output by the frequency-voltage conversion module; and the conversion ratio control module and the frequency-voltage conversion module are used for controlling the frequency-voltage conversion ratio according to the pole pair number of the brushless direct current motor. The invention directly utilizes the rotating speed information of the Hall sensor in the brushless DC motor to realize the real-time display of the rotating speed of the brushless DC motor and effectively judge the running state of the brushless DC motor.)

1. A brushless DC motor rotation speed measuring device is characterized by comprising: an interface module, a frequency-voltage conversion module, a voltage display module, a conversion ratio control module,

the interface module is connected with the frequency-voltage conversion module and is used for accessing Hall sensor signals of the brushless direct current motor;

the frequency-voltage conversion module is connected with the voltage display module and is used for converting a Hall sensor signal of the brushless direct current motor into a linear voltage signal;

the voltage display module displays a voltage value based on the voltage signal output by the frequency-voltage conversion module;

the conversion ratio control module and the frequency-voltage conversion module are used for controlling the frequency-voltage conversion ratio according to the pole pair number of the brushless direct current motor.

2. The apparatus of claim 1, wherein the interface module comprises a connection terminal J1 and a connection terminal J2; the frequency-voltage conversion module comprises a frequency-voltage conversion chip U1, a direct-current power supply VDC1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, an adjustable resistor Rt, a capacitor C1, a capacitor C2 and a capacitor C3; the voltage display module is a voltmeter, wherein:

the frequency-voltage conversion chip U1 comprises 8 pins, and a pin No. 1 of the frequency-voltage conversion chip U1 is used for outputting current and is respectively connected with one end of the resistor R1 and one end of the capacitor C1; the No. 2 pin of the frequency-voltage conversion chip U1 is used for inputting reference current and is connected with one end of the resistor R2; the other end of the resistor R2 is connected with a No. 1 pin of the access end of the adjustable resistor Rt; a No. 5 pin of the frequency-voltage conversion chip U1 is used for being connected with an RC timing circuit and is respectively connected with one end of the resistor R3 and one end of the capacitor C2; the No. 6 pin of the frequency-voltage conversion chip U1 is used for inputting a voltage threshold and is respectively connected with one end of the resistor R4 and one end of the capacitor C3; the No. 7 pin of the frequency-voltage conversion chip U1 is used for controlling comparison input and is respectively connected with one end of the resistor R5 and one end of the resistor R6; the anode of the direct-current power supply VDC1 is respectively connected with the other end of the resistor R3, the other end of the resistor R4, the other end of the resistor R5 and the pin No. 8 of the frequency-voltage conversion chip U1, and the pin No. 8 of the frequency-voltage conversion chip U1 is used for supplying power; the negative electrode of the direct-current power supply VDC1 is respectively connected with the other end of the resistor R1, the other end of the resistor R6, the pin No. 2 of the access end of the adjustable resistor Rt, the other end of the capacitor C1 and the pins No. 3 and No. 4 of the frequency-voltage conversion chip U1, the pin No. 3 of the frequency-voltage conversion chip U1 is used for frequency output, and the pin No. 4 of the frequency-voltage conversion chip U1 is used for grounding; the connection terminal J1 is connected with the other end of the capacitor C3, and the connection terminal J2 is connected with the negative electrode of the direct-current power supply VDC 1; the voltmeter is connected between the pin 1 of the frequency-voltage conversion chip U1 and the negative electrode of the direct-current power supply VDC1 in a bridge mode; and a No. 3 pin of an adjusting end of the adjustable resistor Rt is connected with the conversion ratio control module.

3. The apparatus for measuring the rotational speed of a brushless dc motor according to claim 2, wherein the selected values of the resistor R1 and the capacitor C1 satisfy the following equation:

wherein R1 is the resistance of the resistor R1, and the unit is: omega; c1 is the capacitance value of the capacitor C1, and the unit is: F.

4. the device for measuring the rotating speed of the brushless direct current motor according to claim 2 or 3, wherein the frequency-voltage conversion chip U1 is of a type LM331, and the adjustable resistor Rt is of a type MAX 5407.

5. A use method of a brushless direct current motor rotating speed measuring device is characterized by comprising the following steps:

the method comprises the following steps: the voltage conversion proportion of the frequency-voltage conversion module is adjusted through the conversion proportion control module;

step two: connecting Hall sensor signals of the brushless direct current motor to be measured into a brushless direct current motor rotating speed measuring device through an interface module;

step three: and acquiring the rotating speed of the brushless direct current motor through the voltage display module.

6. The method for using the device for measuring the rotation speed of the brushless DC motor according to claim 5, wherein the step one specific method is as follows: the conversion ratio control module adjusts the resistance value of an adjustable resistor Rt in the frequency-voltage conversion module according to the set pole pair number of the brushless direct current motor, and adjusts the voltage conversion ratio of the frequency-voltage conversion module by changing the resistance value of the adjustable resistor Rt.

7. The method according to claim 5 or 6, wherein the specific formula for obtaining the rotation speed of the brushless dc motor through the voltage display module in the third step is as follows:

wherein, omega is the rotating speed of the brush direct current motor; r is₁Is the resistance of resistor R1; r is₂Is the resistance of resistor R2; r is₃Is the resistance of resistor R3; r is_tIs the resistance value of the adjustable resistor Rt; c. C₂Is the capacitance value of the capacitor C2; p is the pole pair number of the brushless DC motor; v_outIs the value of the voltmeter.

8. Use of a device for measuring the speed of a brushless dc motor according to claim 7, characterized in that the resistance r of the adjustable resistor Rt is such that it is equal to the value of r_tPole pair number p of brushless DC motor and resistance R of resistor R2₂The following formula is satisfied:

r_t＝7×10³×p-r₂

wherein r is_tIs the resistance value of the adjustable resistor Rt; p is the pole pair number of the brushless DC motor; r is₂Is the resistance of resistor R2; "7X 10And 3' is the ratio of the pole pair number of the brushless direct current motor and the resistance value conversion of the adjustable resistor Rt.

Technical Field

The invention relates to a rotating speed measuring device of a brushless direct current motor. And more particularly, to a brushless dc motor rotation speed measuring apparatus that linearly converts rotation speed information of a brushless dc motor into a voltage signal.

Background

The brushless direct current motor is a permanent magnet synchronous motor and has the advantages of high efficiency, fast response, low noise and the like. Therefore, brushless dc motors have been widely used in more and more industries.

Most of drivers of brushless direct current motors on the market do not have rotating speed indicating devices, so that the real-time rotating speed cannot be directly measured after the brushless direct current motors are installed, and the working state of the brushless direct current motors cannot be judged. In order to solve the problem, the conventional method is to add a sensor on a rotating shaft of a brushless direct current motor to realize speed measurement or paste reflective paper on the rotating shaft and then use a photoelectric speed meter to measure, but the former increases unnecessary hardware cost and construction difficulty, and the latter can bring larger rotating speed measurement errors. And the Hall sensor in the brushless DC motor has rotating speed information, and based on the rotating speed information, a rotating speed measuring device of the brushless DC motor, which has a simple structure and is convenient to use, can be designed by utilizing a frequency-voltage conversion chip.

Disclosure of Invention

The invention provides a rotating speed measuring device of a brushless direct current motor and a using method thereof, which aim to solve the problem that the speed measurement is difficult after the brushless direct current motor is installed in the existing production.

The invention provides a brushless direct current motor rotating speed measuring device, which comprises an interface module, a frequency-voltage conversion module, a voltage display module and a conversion proportion control module, wherein:

the interface module is connected with the frequency-voltage conversion module and is used for accessing Hall sensor signals of the brushless direct current motor;

the frequency-voltage conversion module is connected with the voltage display module and is used for converting a Hall sensor signal of the brushless direct current motor into a linear voltage signal;

the voltage display module displays a voltage value based on the voltage signal output by the frequency-voltage conversion module;

and the conversion ratio control module and the frequency-voltage conversion module are used for controlling the frequency-voltage conversion ratio according to the pole pair number of the brushless direct current motor.

Optionally, the interface module comprises a wire terminal J1 and a wire terminal J2; the frequency-voltage conversion module comprises a frequency-voltage conversion chip U1, a direct-current power supply VDC1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, an adjustable resistor Rt, a capacitor C1, a capacitor C2 and a capacitor C3; the voltage display module is a voltmeter, wherein:

the frequency-voltage conversion chip U1 comprises 8 pins, and a pin No. 1 of the frequency-voltage conversion chip U1 is used for outputting current and is respectively connected with one end of the resistor R1 and one end of the capacitor C1; the No. 2 pin of the frequency-voltage conversion chip U1 is used for inputting reference current and is connected with one end of the resistor R2; the other end of the resistor R2 is connected with a No. 1 pin of the access end of the adjustable resistor Rt; a No. 5 pin of the frequency-voltage conversion chip U1 is used for being connected with an RC timing circuit and is respectively connected with one end of the resistor R3 and one end of the capacitor C2; the No. 6 pin of the frequency-voltage conversion chip U1 is used for inputting a voltage threshold and is respectively connected with one end of the resistor R4 and one end of the capacitor C3; the No. 7 pin of the frequency-voltage conversion chip U1 is used for controlling comparison input and is respectively connected with one end of the resistor R5 and one end of the resistor R6; the anode of the direct-current power supply VDC1 is respectively connected with the other end of the resistor R3, the other end of the resistor R4, the other end of the resistor R5 and the pin No. 8 of the frequency-voltage conversion chip U1, and the pin No. 8 of the frequency-voltage conversion chip U1 is used for supplying power; the negative electrode of the direct-current power supply VDC1 is respectively connected with the other end of the resistor R1, the other end of the resistor R6, the pin No. 2 of the access end of the adjustable resistor Rt, the other end of the capacitor C1 and the pins No. 3 and No. 4 of the frequency-voltage conversion chip U1, the pin No. 3 of the frequency-voltage conversion chip U1 is used for frequency output, and the pin No. 4 of the frequency-voltage conversion chip U1 is used for grounding; the connection terminal J1 is connected with the other end of the capacitor C3, and the connection terminal J2 is connected with the negative electrode of the direct-current power supply VDC 1; the voltmeter is connected between the pin 1 of the frequency-voltage conversion chip U1 and the negative electrode of the direct-current power supply VDC1 in a bridge mode; and a No. 3 pin of an adjusting end of the adjustable resistor Rt is connected with the conversion ratio control module.

Optionally, the selected values of the resistor R1 and the capacitor C1 satisfy the following equation:

wherein R1 is the resistance of the resistor R1, and the unit is: omega; c1 is the capacitance value of the capacitor C1, and the unit is: and F.

Optionally, the model of the frequency-voltage conversion chip U1 is LM331, and the model of the adjustable resistor Rt is MAX 5407.

The invention provides a use method of a brushless direct current motor rotating speed measuring device, which comprises the following steps:

the method comprises the following steps: the voltage conversion proportion of the frequency-voltage conversion module is adjusted through the conversion proportion control module;

step two: connecting Hall sensor signals of the brushless direct current motor to be measured into a brushless direct current motor rotating speed measuring device through an interface module;

step three: and acquiring the rotating speed of the brushless direct current motor through the voltage display module.

Optionally, the first specific method of the step is: the conversion ratio control module adjusts the resistance value of an adjustable resistor Rt in the frequency-voltage conversion module according to the set pole pair number of the brushless direct current motor, and adjusts the voltage conversion ratio of the frequency-voltage conversion module by changing the resistance value of the adjustable resistor Rt.

Optionally, in the third step, a specific formula for obtaining the rotation speed of the brushless dc motor through the voltage display module is as follows:

wherein, omega is the rotating speed of the brush direct current motor; r is₁Is the resistance of resistor R1; r is₂Is the resistance of resistor R2; r is₃Is the resistance of resistor R3; r is_tIs the resistance value of the adjustable resistor Rt; c. C₂Is the capacitance value of the capacitor C2; p is the pole pair number of the brushless DC motor; v_outIs the value of the voltmeter.

Optionally, the resistance r of the adjustable resistor Rt_tPole pair number p of brushless DC motor and resistance R of resistor R2₂The following formula is satisfied:

r_t＝7×10³×p-r₂

wherein r is_tIs the resistance value of the adjustable resistor Rt; p is the pole pair number of the brushless DC motor; r is₂Is the resistance of resistor R2; "7 × 103" is a ratio of the number of pole pairs of the brushless dc motor to the resistance value conversion of the adjustable resistor Rt.

The invention at least comprises the following beneficial effects:

1. according to the invention, under the condition that no additional rotating speed sensor is used, the rotating speed information is obtained by collecting the signals of the Hall sensor in the brushless direct current motor, so that the stability and the accuracy of the measured data of the rotating speed testing device are greatly improved.

2. The brushless direct current motor speed measuring device adopted by the invention has the characteristics of low cost, convenience in installation and debugging and the like, and is particularly suitable for the conditions of limited measuring space or inconvenience in installation of a sensor and the like.

3. The invention realizes the adjustment of the voltage conversion ratio through the conversion ratio control module and the adjustable resistor, realizes the test of the brushless DC motor with different pole pair numbers, has no influence of the pole pair number on the corresponding relation of the voltage and the rotating speed, can visually find the rotating speed conditions of the brushless DC motor with different pole pair numbers through the voltage value, and has strong adaptability and simple and convenient operation.

Drawings

The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:

FIG. 1 is a schematic circuit diagram of a brushless DC motor rotation speed measuring device according to an embodiment of the present invention;

FIG. 2 is a waveform diagram illustrating the output of the capacitor charging and discharging of a brushless DC motor rotation speed measuring device according to an embodiment of the present invention;

fig. 3 is a schematic diagram illustrating voltage and rotation speed indication of a brushless dc motor rotation speed measuring device according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a brushless direct current motor rotating speed measuring device, which comprises an interface module, a frequency-voltage conversion module, a voltage display module and a conversion proportion control module, wherein:

the interface module is connected with the frequency-voltage conversion module and is used for accessing Hall sensor signals of the brushless direct current motor;

the frequency-voltage conversion module is connected with the voltage display module, converts a Hall sensor signal of the brushless direct current motor into a linear voltage signal and indicates the rotating speed on the voltage display module;

and the conversion ratio control module and the frequency-voltage conversion module are used for controlling the frequency-voltage conversion ratio according to the pole pair number of the brushless direct current motor.

As shown in fig. 1, the interface module includes a connection terminal J1 and a connection terminal J2; the frequency-voltage conversion module comprises a frequency-voltage conversion chip U1, a direct-current power supply VDC1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, an adjustable resistor Rt, a capacitor C1, a capacitor C2 and a capacitor C3; the voltage display module is a voltmeter; the conversion ratio control module comprises a controller and a key, wherein:

the frequency-voltage conversion chip U1 is preferably LM331, and comprises 8 pins; the optimal type of the adjustable resistor Rt is MAX5407, the adjustable resistor Rt comprises 3 pins, wherein pins 1 and 2 of the adjustable resistor Rt are pins of an access end, and pin 3 is a pin of a resistance value adjusting end; the No. 1 pin of the frequency-voltage conversion chip U1 is used for current output and is respectively connected with one end of a resistor R1 and one end of a capacitor C1; the No. 2 pin of the frequency-voltage conversion chip U1 is used for inputting reference current and is connected with one end of a resistor R2; the other end of the resistor R2 is connected with a No. 1 pin of the adjustable resistor Rt; a No. 5 pin of the frequency-voltage conversion chip U1 is used for being connected with an RC timing circuit and is respectively connected with one end of a resistor R3 and one end of a capacitor C2; a pin 6 of the frequency-voltage conversion chip U1, which is used for inputting a voltage threshold, and is respectively connected to one end of a resistor R4 and one end of a capacitor C3; a No. 7 pin of the frequency-voltage conversion chip U1, which is used for controlling comparison input and is respectively connected with one end of a resistor R5 and one end of a resistor R6; the anode of the direct-current power supply VDC1 is respectively connected with the other end of the resistor R3, the other end of the resistor R4, the other end of the resistor R5 and the No. 8 pin of the frequency-voltage conversion chip U1, and the No. 8 pin of the frequency-voltage conversion chip U1 is used for supplying power; the negative electrode of the direct-current power supply VDC1 is respectively connected with the other end of the resistor R1, the other end of the resistor R6, the pin No. 2 of the adjustable resistor Rt, the other end of the capacitor C1 and the pins No. 3 and No. 4 of the frequency-voltage conversion chip U1, the pin No. 3 of the frequency-voltage conversion chip U1 is used for frequency output, and the pin No. 4 of the frequency-voltage conversion chip U1 is used for grounding; the connection terminal J1 is connected with the other end of the capacitor C3, and the connection terminal J2 is connected with the negative electrode of the direct-current power supply VDC 1; the voltmeter is connected between the pin 1 of the frequency-voltage conversion chip U1 and the negative electrode of the direct-current power supply VDC1 in a bridge mode; and a No. 3 pin of the adjustable resistor Rt is connected with the conversion ratio control module.

The use method of the brushless dc motor rotation speed measuring device shown in fig. 1 further includes the following steps:

step A1: inputting the pole pair number of the brushless direct current motor into a controller through a key, adjusting the resistance value of the adjustable resistor Rt by the controller based on the input pole pair number, and adjusting the voltage conversion proportion of the frequency-voltage conversion module by changing the resistance value of the adjustable resistor Rt;

step A2: connecting a connecting terminal J1 with a signal output line of a certain phase Hall sensor of the brushless direct current motor to be tested, and connecting a connecting terminal J2 with the negative pole of a power supply line of the Hall sensor of the brushless direct current motor to be tested;

step A3: and reading the numerical value of the voltmeter, and acquiring the rotating speed through the numerical value of the voltmeter.

In the step a2, the connection terminal J2 is connected to the negative electrode of the power supply line of the hall sensor of the brushless dc motor to be measured, so that the ground signal of the rotating speed measuring device of the brushless dc motor is the same as the ground signal of the hall sensor of the brushless dc motor, and the measuring device can obtain the square wave signal with accurate level amplitude in the hall sensor. Connecting a connecting terminal J1 with a signal output line of a certain phase Hall sensor of the brushless DC motor to be tested, wherein the signal frequency f of the Hall sensor received by the connecting terminal J1_hallA differential circuit consisting of a resistor R4 and a capacitor C3 is added to a No. 6 pin of a frequency-voltage conversion chip U1, wherein the capacitor C3 is a filter capacitor, and the anti-interference capability of the conversion capacitor is improved.

FIG. 2 is a waveform diagram of the output of capacitor charging and discharging of a brushless DC motor speed measuring device according to the present invention, V_C1The curve is the voltage change curve, V, on the capacitor C1_C2The curve is the voltage variation curve on the capacitor C2. When the signal frequency f of the Hall sensor_hallWill generate a negative spike on pin 6 of the frequency-to-voltage conversion chip U1 via the differentiating circuit when the falling edge of (a) arrives. The voltage of the direct current power supply VDC1 is V_DC1When the negative spike is greater than V_DC1The internal flip-flop of the/3 time frequency voltage conversion chip U1 is set, the internal current source charges the capacitor C1, and the direct current power supply VDC1 charges the capacitor C2 through R3. When the voltage on the capacitor C1 is more than 2V_DC1And 3, resetting a trigger in the frequency-voltage conversion chip U1, discharging the capacitor C1 through the resistor R1, and rapidly discharging the timing capacitor C2 to finish one charging and discharging process. Thereafter, the circuit repeats the above operation process every time a charge and discharge process is performed, therebyFrequency/voltage conversion is achieved. t is t₁The segment represents the charging process of the capacitor C1 and the capacitor C2, t₂The segment represents the discharge process of the capacitor C1 and the capacitor C2.

To ensure the frequency f of the input signal_hallAfter the differential signal is differentiated to have enough amplitude to trigger the internal trigger of the frequency-voltage conversion chip U1, the capacitor C3 is not suitable to be too small, but the capacitor C3 is smaller, which is beneficial to improving the anti-interference capability of the conversion circuit. The resistor R1 and the capacitor C1 form a low-pass filter, and the capacitor C1 is selected to be larger, so that the output voltage V can be reduced_outThe capacitor C1 is selected to be small, so that the response speed of the output response can be improved when the input pulse frequency is changed.

The selection of the resistor R1 and the capacitor C1 satisfies the following conditions:

to ensure a smaller ripple and a higher effect speed of the output voltage Vout. Wherein R1 is the resistance of the resistor R1, and the unit is: omega; c1 is the capacitance value of the capacitor C1, and the unit is: F.

the resistance R of the resistor R1 used in this embodiment₁140k Ω, resistance R of resistor R2₂Resistance R of the resistor R3, 10k Ω₃12k Ω, resistance R of resistor R4₄1k Ω, resistance R of resistor R5₅1k Ω, resistance R of resistor R6₆1k Ω, capacitance C of the capacitor C1₁0.01uF, capacitance value C of capacitance C2₂0.01uF, capacitance value C of capacitance C3₃0.01 uF; the frequency-voltage chip U1 selects the frequency-voltage conversion chip LM331 or the frequency-voltage converter MURC 415; the motor parameters used were as follows: rated voltage is 24V, rated current is 7A, and rated power is 120W; a voltmeter with the measuring range of 0-5V is selected.

Example 1: the pole pair number p of the brushless direct current motor is 3, and the actual rotating speed of the brushless direct current motor is 3000 r/m. When the rotating speed of the brushless DC motor needs to be detected, the output frequency f of the switch type Hall sensor_hall150 Hz; the resistance value of the adjustable resistor Rt is adjusted by changing the pole pair number p to 3, and the formula is as follows:

r_t＝7×10³×p-r₂＝7×10³×3-10×10³＝11×10³(Ω)

the signal frequency f of the Hall sensor can be passed_hallValue V of voltmeter_outRelation-knowing voltmeter value V_outThe concrete formula is as follows:

then passes through the value V of the voltmeter_outThe relation between the actual rotating speed and the rotating speed omega of the brushless direct current motor reversely deduces the actual rotating speed of the brushless direct current motor, and the specific formula is as follows:

example 2: the pole pair number p of the brushless direct current motor is 4, and the actual rotating speed of the brushless direct current motor is 3000 r/m. When the rotating speed of the brushless DC motor needs to be detected, the output frequency f of the switch type Hall sensor_hall200 Hz; the resistance value of the adjustable resistor Rt is adjusted by changing the pole pair number p to 4, and the formula is as follows:

r_t＝7×10³×p-r₂＝7×10³×4-10×10³＝18×10³(Ω)

the signal frequency f of the Hall sensor can be passed_hallValue V of voltmeter_outRelation-knowing voltmeter value V_outThe concrete formula is as follows:

then passes through the value V of the voltmeter_outThe relation between the actual rotating speed and the rotating speed omega of the brushless direct current motor reversely deduces the actual rotating speed of the brushless direct current motor, and the specific formula is as follows:

FIG. 3 is a schematic diagram of the indication of the voltmeter in the two examples, and r in the calculation formula of the two examples₁Is the resistance of the resistor R1, and has the unit: omega; r is₂Is the resistance of the resistor R2, and has the unit: omega; r is₃Is the resistance of the resistor R3, and has the unit: omega; r is_tIs the resistance value of the variable resistor Rt, and the unit is: omega; c. C₂Is the capacitance value of the capacitor C2, and the unit is: f; "2.09" is the coefficient of frequency-to-voltage conversion.

In examples 1 and 2, after the frequency signals output by the hall sensors are processed by the device, the displayed voltage values are the same, namely when the pole pair number of the brushless direct current motor changes, the device can adjust the resistance value of the variable resistor Rt to enable the value V of the voltmeter to be the same_out(V) Signal frequency f of one-phase Hall sensor of brushless DC Motor connected to connection terminal J1_hallThe relation between the numbers (Hz) is changed correspondingly, namely, the conversion coefficient is changed through the number of pole pairs and the resistance value of the variable resistor Rt adjusted according to the number of pole pairs when the voltage value is calculated through the signal frequency through a formula, so that the numerical value of the voltmeter and the rotating speed of the brushless direct current motor are kept in a fixed relation all the time and are not influenced by the number of pole pairs of the brushless direct current motor.

It is obvious that those skilled in the art can obtain various effects not directly mentioned according to the respective embodiments without trouble from various structures according to the embodiments of the present invention. While the invention/embodiments of the invention have been disclosed above, it is not limited to the applications listed in the description and the embodiments. It can be applied to all kinds of fields suitable for the present invention. Additional modifications will readily occur to those skilled in the art. It is therefore intended that the invention not be limited to the exact details and illustrations described and illustrated herein, but fall within the scope of the appended claims and equivalents thereof.