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“This system mainly realizes the measurement of (auditory) nerve-motor response. The method is to detect the sound of the starting gun through the sound sensor, use the acceleration sensor to detect the moment when the athlete starts running, record the time it takes the athlete to hear the starting gun and start running, and then transmit the data to the base station through the wireless data transmission module for recording and processing. The system consists of three parts: the reaction time measurement module, the communication module, and the data recording processing module. The structure is shown in Figure 1.
Authors: Song Peng, Qian Yuefeng, Dou Zhen
Response time refers to the time required after a stimulus is applied to an organism to the onset of an apparent response, that is, the time interval between the stimulus and the response. At present, most of the determination of athletes’ reaction ability in our country is realized by simple acousto-optic reaction time measuring instrument or computer simulation. However, these test methods are greatly affected by the external environment and people’s subjective psychological factors, and cannot accurately and objectively reflect the athlete’s neural response ability in sports. This paper implements a system for measuring athlete’s (auditory) neuro-motor response time to improve the start speed of the athlete after hearing the starting gun. The system detects the time required by the athlete to hear the starting gun and starts running through the sound sensor and the acceleration sensor, that is, when the athlete’s nerve-motor response, and then transmits the data to the PC through the wireless data transmission module for Display, and can be based on the response time. The records are processed and drawn into reaction time curves, which can intuitively understand the changes and trends of athletes’ reaction times.
System structure and its principle
This system mainly realizes the measurement of (auditory) nerve-motor response. The method is to detect the sound of the starting gun through the sound sensor, use the acceleration sensor to detect the moment when the athlete starts running, record the time it takes the athlete to hear the starting gun and start running, and then transmit the data to the base station through the wireless data transmission module for recording and processing. The system consists of three parts: the reaction time measurement module, the communication module, and the data recording processing module. The structure is shown in Figure 1.
Figure 1 System structure block diagram
The reaction time measurement module uses a single-chip microcomputer as the core component, plus a sound sensor and an acceleration sensor detection circuit, records the athletes’ starting reaction time through the internal counter of the single-chip microcomputer, encodes the recorded data according to a certain format, and sends it to the wireless sending module through the serial port , to realize wireless communication with PC.
The communication module mainly uses PTR2000 wireless data transmission module to realize wireless data transmission.
The data recording processing module receives the data transmitted by the wireless data transmission module through serial communication, and sends it to the base station formed by the PC machine for recording, processing and display.
System Design Fundamentals
Measurement preparation and system self-test
The system sets a button on the measurement module at the time of reaction. Before each measurement, press this button to start the system self-check, and check the status of various components connected to it through the single-chip microcomputer, such as memory, acceleration sensor, sound sensor, etc., and wireless Whether the communication system works normally. Through the wireless transmission module, the detected state of each component is sent to the receiving end. If the receiving end receives a normal signal, the recording end can notify the start of measurement; if it cannot be received, it must be checked, debugged, or replaced. , the measurement can be started until the receiver receives a normal signal.
After the system self-test is completed, if the various components are working properly, the reaction time can be measured. After the sound sensor detects the sound signal of the starting gun, the counter starts counting, and queries the signal of the acceleration sensor, stops counting after detecting the signal of the acceleration sensor, and saves the count value in the sending buffer, and the data acquisition process ends.
Wireless transmission and reception of data
After the data acquisition of the microcontroller is completed, the wireless transmission of the data is started. Before sending, the collected data is encoded according to the requirements of the wireless data transmission module, and then the data is sent through the wireless data transmission module in the order from high to low. At the wireless receiving end, the received data is sent to the PC for processing and display through level conversion and RS-232 serial interface.
Processing and Display of Data
After receiving the data from the RS-232 serial interface, the base station formed by the PC will process, store, display and analyze the data through the athlete’s starting reaction processing software.
System Hardware Design
From the hardware point of view, the system can be divided into a single chip module, a sound detection module, a motion detection module and a wireless data transmission module.
In this system, considering that the measurement device is installed on the calf of the athlete, there is not much demand for the number of input and output ports. Therefore, when choosing a single-chip microcomputer, small size and low power consumption should be selected as the core of the front-end data measurement of the system. Parts, this system adopts the 8-bit microcontroller AT89C2051 produced by Atmel Company.
sound detection module
Sound detection is a key part of the system design, which requires good sensitivity and anti-interference ability.
Electret microphone is a kind of miniature acoustoelectric converter, which has the advantages of high sensitivity, wide frequency response range and small size. In this system, the electret microphone is selected as the sound sensor of the sound detection part, and it is used to convert the sound signal into an electrical signal.
The difficulty and focus of the sound detection module design is to filter out the noise signal. In the design process of this module, after many experiments, the circuit and related parameters of this module are finally determined. The system adopts the amplitude comparison method to realize the function of sound detection. Because the sound signal of the starting gun is generally larger in amplitude, it can be directly amplified, and compared with the threshold voltage through the comparator, when the sound signal is greater than a certain amplitude, a flip signal is generated. The main consideration is how to amplify the weak signal detected by the electret microphone. In this system, the triode 9013 is used to form a single-stage amplifying circuit to amplify the signal. After many experiments, it is found that when the output voltage is greater than 4V, the vibration amplitude of the sound signal is large. Coupled with the comparison circuit, the sound detection circuit of the system is formed, as shown in Figure 2. In this circuit, a voltage divider with R5 and R6 is used to generate a threshold voltage, which is set to 4V in the actual design. The OUT2 of the voltage comparator LM339 generates a self-checking voltage of the sound signal. If there is no fault in the sound detection, it should output a high level; OUT1 is connected to the P1.2 port of the single-chip microcomputer as the sound detection signal output pin, and a pulse signal is output when the starting gun sounds.
Figure 2 Sound detection circuit
motion detection module
The motion detection module selects the single-chip acceleration sensor ADXL105 produced by ADI Company in the United States as the motion detection sensor, which includes an acceleration sensor and a signal conditioner. This is a differential force-balanced acceleration sensor, which uses the method of changing the gap to convert the measured acceleration into the capacitance change of the capacitor. The internal capacitive voltage divider circuit provides an analog output voltage proportional to the magnitude of the acceleration, and its phase depends on the direction of the acceleration, which can be connected to the input end of the ADC without any additional active devices. It can be used to measure static acceleration (such as gravitational acceleration or inclination, etc.), and can be used to measure dynamic acceleration (such as vibration, etc.).
Since ADXL105 can directly output analog signal, it only needs to compare the output voltage of ADXL105 with the threshold voltage through the comparator, and output high level when the acceleration is greater than a certain threshold. Its principle circuit is shown in Figure 3. The OUT3 pin of LM339 outputs the motion detection signal, which is connected to the P1.4 port of the microcontroller; the OUT4 pin outputs the motion self-test signal, which is connected to the P1.5 port of the microcontroller.
Figure 3 Schematic diagram of the motion detection module circuit
Wireless data transmission module
System software design
According to the design requirements of the system, the system software is divided into two parts, the transmitter software and the receiver software, which are designed respectively.
The software of the MCU part can be divided into the following modules: self-checking module, transmitting module and timing module. The flow chart of the main program of the single-chip microcomputer is shown in Figure 4.
Figure 4 The flow chart of the main program of the single-chip microcomputer
In this system, the receiving end is a PC, which is programmed in VB language. In terms of standard RS-232 serial communication, VB provides a communication control Mscomm with powerful functions. This control can set the data sending and receiving of serial communication, and set the serial port status and the information format and protocol of serial communication. This is a standard 10-bit serial communication, including 8-bit data, 1-bit start bit and 1-bit stop bit. In the process of sending or receiving data, the OnComm event is triggered, and the properties of the CommEvent are accessed programmatically to understand the type of the communication event and perform their own processing. Each communication control corresponds to a serial port, and multiple communication controls can be designed to access multiple communication ports. The control provides full-featured serial port data sending and receiving functions. The Mscomm control has two processing methods: the event-driven method, which captures and handles communication errors and events by the OnComm event of the Mscomm control; the query method, which is obtained by checking the value of the CommEvent property. Judge events and errors. The event-driven approach is adopted in this system.
Through the powerful graphic programming method of VB programming tool, the drawing of the athlete’s response curve can be realized. And the graph can be enlarged, reduced and moved to easily show the changing trend of the athlete’s reaction. Based on the design of the above program modules, this software realizes the real-time data acquisition and transmission/reception and stable display, which makes the whole system have high practical value.
Through the test, the minimum resolution of the system is 2ms, the measurement range is 0 “18.2s, the transmission distance ≥ 10 meters, the data transmission rate ≥ 1200 bps, the operating temperature range is -25℃”40℃, the working voltage is DC 5V±10 %, the measurement module is powered by dry or rechargeable batteries.
The method used in this measurement system is at the leading level in China. Compared with the previous simulation measuring instrument for starting reaction time, it can not only directly and accurately measure the starting reaction time of athletes on the sports field, but also analyze and synthesize the reaction time. Promote the research on athletes’ reaction time and improve the training level of athletes, and provide scientific reference for the selection and training of athletes.