A trolley ultra-low speed measuring device

Abstract

The utility model discloses a trolley ultralow speed measuring device belongs to electronic measurement technical field, including the hall sensor of installation on the trolley wheel support and the magnet of installation on the trolley drive wheel, the inductive distance between hall sensor and magnet is 1 3mm, the output of hall sensor is connected with signal conditioning circuit, the output of signal conditioning circuit is connected with microcontroller, the serial communication pin of microcontroller is connected with bluetooth module, the display drive pin of microcontroller is connected with display screen, the utility model adopts the inductive mode of hall sensor and magnet, and there is no mechanical wear, and the reliability is high, and again based on the cooperation of hall sensor, signal conditioning circuit and microcontroller, can still keep very high measuring accuracy and stability in 0.05m / s to 0.88m / s ultralow speed range, realizes the wireless transmission of measurement data through the setting of bluetooth module.

Description

Technical Field

[0001] This utility model relates to the field of electronic measurement technology, specifically to a low-speed measurement device for a small car, which is a high-precision speed measurement device and its control system suitable for low-speed motion scenarios such as ChemECar (a car racing competition). Background Technology

[0002] The Chemical Energy Car Competition requires participating teams to design a car powered and precisely controlled by a chemical reaction. The car must generate power through chemical reactions (such as acid-base neutralization, metal corrosion, and gas generation) and simultaneously use another chemical reaction (such as the iodine clock reaction or enzyme catalysis) to achieve a timed stop. The closer the car's front end is to the finish line, the higher the score, given a given load (0-500ml of water) and distance (15-30 meters). Therefore, the car's speed stability and accurate measurement are of extremely high importance, and the speed range is usually very low, between 0.05m / s and 0.8m / s.

[0003] In ultra-low speed ranges of micro-low speed motion scenarios such as chemical energy vehicle races, existing measurement methods include photoelectric encoders and GPS modules. However, photoelectric encoders require precise optical path alignment, are easily affected by environmental dust and oil, and their performance may degrade under strong outdoor light. GPS modules, on the other hand, have limitations such as high power consumption and inability to work indoors or in shaded environments, which affect measurement accuracy and cannot meet the high standards required for competitions. Utility Model Content

[0004] The purpose of this invention is to provide a vehicle ultra-low speed measurement device. By measuring speed based on a Hall sensor, it achieves non-contact high-precision measurement and wireless data transmission in the ultra-low speed range of 0.05m / s to 0.8m / s, thereby improving measurement accuracy, meeting the high standards required for competitions, and solving the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a vehicle ultra-low speed measuring device, comprising a Hall sensor mounted on the vehicle wheel bracket and a magnet mounted on the vehicle drive wheel, wherein the sensing distance between the Hall sensor and the magnet is 1-3mm, the output terminal of the Hall sensor is connected to a signal conditioning circuit, the output terminal of the signal conditioning circuit is connected to a microcontroller, a Bluetooth module is connected to the serial communication pin of the microcontroller, and a display screen is connected to the display driver pin of the microcontroller.

[0006] Preferably, the signal conditioning circuit includes a comparator U1, the positive terminal of which is connected to a Hall sensor, the negative terminal of which is connected to a resistor R1 for connecting to a 3.3V voltage and an adjustable resistor RP1 for grounding, and the output terminal of the comparator U1 is connected to a microcontroller.

[0007] Preferably, the microcontroller has a built-in timer for accurately measuring pulse time intervals, and the timer operates in an input capture mode.

[0008] Preferably, the Hall sensor includes a Hall chip U2, the VDD terminal of the Hall chip U2 is connected to a 3.3V power supply, the VDD terminal of the Hall chip U2 and the connection terminal of the 3.3V power supply are respectively connected to a ground capacitor C1 and a resistor R4, one end of the resistor R4 is connected to the output terminal of the Hall chip U2, and the connection terminal of the output terminal resistor R4 of the Hall chip U2 is connected to a signal conditioning circuit, and the connection terminal of the output terminal resistor R4 of the Hall chip U2 is also connected to a ground capacitor C2.

[0009] Preferably, the microcontroller is an STM32 microcontroller, and the microcontroller is provided with a USART interface for connecting to a Bluetooth module.

[0010] Preferably, the Bluetooth module includes an HC-05 chip, which has a connection interface for connecting to a 3.3V power supply and ground.

[0011] Preferably, the display screen is an OLED display screen, and the display screen uses I... 2 The C interface connects to the microcontroller.

[0012] Compared with the prior art, the beneficial effects of this utility model are:

[0013] 1. This utility model adopts the sensing method of Hall sensor and magnet, which has no mechanical wear and high reliability. Based on the cooperation of Hall sensor, signal conditioning circuit and microcontroller, it can still maintain extremely high measurement accuracy and stability in the ultra-low speed range of 0.05m / s to 0.88m / s.

[0014] 2. This utility model enables wireless transmission of measurement data through the Bluetooth module, facilitating connection with terminals such as mobile phones and computers, enabling data recording and analysis, and is suitable for battery power supply.

[0015] 3. This utility model, through the cooperation of the display screen and the microcontroller, can provide real-time feedback of speed information and combine it with wireless transmission for subsequent analysis, thus meeting the dual needs of competition debugging and performance analysis. Attached Figure Description

[0016] Figure 1 This is a block diagram of the modules of this utility model;

[0017] Figure 2 This is a schematic diagram of the signal conditioning circuit of this utility model;

[0018] Figure 3 This is the circuit diagram of the Hall sensor of this utility model;

[0019] Figure 4 This is a schematic diagram of the display screen circuit of this utility model;

[0020] Figure 5 This is a schematic diagram of the installation of the device of this utility model on a chemical trolley wheel. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0022] Please see Figure 1-4 This utility model provides a technical solution: a low-speed measurement device for a small vehicle, comprising a Hall sensor mounted on the wheel bracket of the small vehicle and a magnet mounted on the drive wheel of the small vehicle, wherein the sensing distance between the Hall sensor and the magnet is 1-3mm. Figure 5 As shown, the Hall sensor U1 is fixed to the suspension of the car chassis by a bracket. The magnet is firmly embedded inside the drive wheel of the car, maintaining a constant distance of approximately 2mm from the Hall sensor, and rotates with the wheel. The output terminal of the Hall sensor is connected to a signal conditioning circuit, and the output terminal of the signal conditioning circuit is connected to a microcontroller. A Bluetooth module is connected to the serial communication pin of the microcontroller, and a display screen is connected to the display driver pin of the microcontroller. The Hall sensor senses the change in the magnetic field of the magnet fixed on the wheel of the chemical energy vehicle. The field change generates a voltage signal, and its 1-3mm sensing distance ensures a balance between signal strength and anti-interference capability. The voltage signal generated by the magnetic field change is shaped into a 0 or 3.3V digital pulse by the signal conditioning circuit, eliminating noise interference, improving signal clarity, and providing a stable input for the microcontroller. The microcontroller calculates the speed value based on the time interval and the preset wheel circumference parameter. The calculated speed data is displayed in real time on the OLED display via the I2C protocol, and sent to the HC-05 chip via the USART serial port. The HC-05 chip then wirelessly transmits the data to connected external terminals such as mobile phones or computers.

[0023] like Figure 2As shown, the signal conditioning circuit includes a comparator U1. The positive terminal of the comparator U1 is connected to a Hall sensor, and the negative terminal of the comparator U1 is connected to a resistor R1 for connecting to a 3.3V voltage and an adjustable resistor RP1 for grounding. The output terminal of the comparator U1 is connected to a microcontroller. The analog signal output by the Hall sensor is shaped into a digital pulse signal through the shaping circuit of the comparator U1. The comparator U1 connects to the Hall sensor with its positive terminal and to a 3.3V voltage divider circuit (resistor R1 and adjustable resistor RP1) with its negative terminal to achieve signal shaping with an adjustable threshold. The adjustable resistor RP1 allows the trigger threshold to be adjusted according to the actual magnetic field strength, enhancing environmental adaptability. The output terminal is directly connected to the microcontroller to ensure fast response and low-latency transmission of the digital pulse signal.

[0024] The microcontroller has a built-in timer for accurately measuring pulse time intervals. This timer operates in input capture mode. The STM32 has a built-in high-precision timer that accurately measures pulse time intervals through input capture mode. Input capture mode can automatically record pulse edge timestamps, eliminating software timing errors and improving speed calculation accuracy (especially suitable for ultra-low speed scenarios). The timer's high resolution (e.g., a 72MHz clock) ensures microsecond-level time measurement, meeting the speed resolution requirements under low-speed wheel circumference parameters.

[0025] like Figure 3 As shown, the Hall sensor includes a Hall chip U2. The VDD terminal of the Hall chip U2 is connected to a 3.3V power supply. The connection terminals of the VDD terminal and the 3.3V power supply of the Hall chip U2 are respectively connected to a ground capacitor C1 and a resistor R4. One end of the resistor R4 is connected to the output terminal of the Hall chip U2, and the connection terminal of the resistor R4 at the output terminal of the Hall chip U2 is connected to a signal conditioning circuit. The connection terminal of the resistor R4 at the output terminal of the Hall chip U2 is also connected to a ground capacitor C2. The VDD terminal of the Hall chip U2 is connected to the 3.3V power supply, and an RC filter circuit is formed by the ground capacitor C1 and the resistor R4 to suppress power supply ripple. The output terminal is further filtered by the current limiting resistor R4 and the ground capacitor C2 to eliminate high-frequency noise and ensure the stability of the output signal. The combination of the resistor R4 and the ground capacitor C2 forms a low-pass filter to optimize the filtering effect.

[0026] The microcontroller is an STM32 microcontroller, model STM32F103C8T6, and the microcontroller is equipped with a USART interface for connecting to a Bluetooth module.

[0027] The Bluetooth module includes an HC-05 chip, which has connection interfaces for connecting a 3.3V power supply and ground. The HC-05 chip supports the Bluetooth 2.0 protocol and communicates with the STM32 microcontroller via a USART interface to achieve wireless data transmission. The USART interface provides full-duplex communication, ensuring real-time upload of speed data to terminal devices (such as mobile phones or computers). The Bluetooth module's 3.3V power supply is compatible with the STM32's logic levels, simplifying circuit design and reducing power consumption.

[0028] The display screen is an OLED display screen, such as Figure 4 As shown, the display screen includes an SSD1306 chip U4. A capacitor C4 is connected between pins 2 and 3 of the SSD1306 chip U4. A capacitor C3 is connected between pins 4 and 5 of the SSD1306 chip U4. A resistor R10, a diode D1, and a capacitor C9 connected in parallel are connected to pin 14 of the SSD1306 chip U4. A resistor R12 for connecting to VCC and a resistor R11 for grounding are connected in parallel to pin 15 of the SSD1306 chip U4. A resistor R7 is connected to pin 18 of the SSD1306 chip U4. A resistor R6 is connected to pin 19 of the SSD1306 chip U4, and the other ends of resistors R6 and R7 are connected in parallel. Pins 18 and 19 of the SSD1306 chip U4 are used to connect to a microcontroller. The display screen is connected via I... 2 The C interface connects to the microcontroller, and the OLED display connects via I... 2 The C interface connects to the STM32 microcontroller, requiring only two wires (SCL and SDA) for data transmission, saving microcontroller pin resources; 2 The C protocol supports multiple device mounting, facilitating the future expansion of other sensors (such as temperature and humidity sensors); the self-emissive nature of OLEDs eliminates the need for backlighting, reducing power consumption and making them suitable for battery-powered vehicle devices.

[0029] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for measuring the ultra-low speed of a vehicle, characterized in that: The device includes a Hall sensor mounted on the wheel bracket of the car and a magnet mounted on the drive wheel of the car. The sensing distance between the Hall sensor and the magnet is 1-3mm. The output terminal of the Hall sensor is connected to a signal conditioning circuit. The output terminal of the signal conditioning circuit is connected to a microcontroller. A Bluetooth module is connected to the serial communication pin of the microcontroller. A display screen is connected to the display driver pin of the microcontroller.

2. The ultra-low speed measuring device for a trolley according to claim 1, characterized in that: The signal conditioning circuit includes a comparator U1, the positive terminal of which is connected to a Hall sensor, and the negative terminal of which is connected to a resistor R1 for connecting to a 3.3V voltage and an adjustable resistor RP1 for grounding. The output terminal of the comparator U1 is connected to a microcontroller.

3. The ultra-low speed measuring device for a trolley according to claim 2, characterized in that: The microcontroller has a built-in timer for accurately measuring pulse time intervals, and the timer operates in input capture mode.

4. The ultra-low speed measuring device for a trolley according to claim 3, characterized in that: The Hall sensor includes a Hall chip U2. The VDD terminal of the Hall chip U2 is connected to a 3.3V power supply. The connection terminals of the VDD terminal and the 3.3V power supply of the Hall chip U2 are respectively connected to a ground capacitor C1 and a resistor R4. One end of the resistor R4 is connected to the output terminal of the Hall chip U2, and the connection terminal of the output terminal resistor R4 of the Hall chip U2 is connected to a signal conditioning circuit. The connection terminal of the output terminal resistor R4 of the Hall chip U2 is also connected to a ground capacitor C2.

5. The ultra-low speed measuring device for a trolley according to claim 4, characterized in that: The microcontroller is an STM32 microcontroller, and the microcontroller is provided with a USART interface for connecting to a Bluetooth module.

6. The ultra-low speed measuring device for a trolley according to claim 5, characterized in that: The Bluetooth module includes an HC-05 chip, which has a connection interface for connecting to a 3.3V power supply and ground.

7. The ultra-low speed measuring device for a trolley according to claim 6, characterized in that: The display screen is an OLED display screen, and the display screen is connected via I 2 The C interface connects to the microcontroller.

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