At present, an electronic therapy device that uses two electrode sheets symmetrically covering a human body part is produced by the pulsating voltage on the electrode sheet and the resistance of the body part, and generates a pulsating current that the human body can perceive at the treatment site, stimulating the nerve muscles, causing them to contract and Relaxation produces a motor effect for therapeutic purposes. However, there are only a few pulsating voltages generated by this type of therapeutic apparatus on the market. Since the frequency of the pulsating current is fixed, if a certain treatment site receives its pulsation for a long time, it will produce an anti-therapeutic effect, causing spontaneous tension, thereby reducing the therapeutic effect. In order to solve this problem, the random music signal sent by the MP3 is introduced into the therapy device, and the audio signal is modulated with the 2.4 kHz intermediate frequency treatment frequency to generate a plurality of pulsating voltages and pulsating currents whose frequency cycles are constantly changing. They interact with the fluctuations in the music signal, allowing the patient to receive treatment while enjoying the music they like, distracting and relieving tension, which helps to improve the treatment.
An electronic therapy device design based on embedded device AT89C51SNDIC is proposed, and D/A, mass memory, keyboard and display are expanded to realize basic MP3 function; AT89C5lSNDlC is controlled to generate audio and 2.4 kHz IF signal, using digital The circuit completes the frequency modulation of the two signals, and after amplification, the output ripple therapy voltage is isolated by the transformer.
2 Working principleThe hardware structure of the electronic therapy device system based on the embedded device 89C51SNDIC is shown in Figure 1. It is divided into three parts: signal generation and control module, FM output module and power module.
The signal generation and control module is composed of 89C51SNDIC microcontroller, mass memory, keyboard, USB port, liquid crystal display, D/A converter, audio amplification and other parts. When the USB port of the therapy device is inserted into the USB interface of the computer, the U disk function is executed after being detected by the MCU, and the selected MP3 song can be copied to the U disk (therapeutic device). When the USB port of the therapy device is not plugged into the USB port of the computer, the therapy device can be used as an MP3 broadcaster. Use the function keys to set the song, treatment time, volume, and control the therapy device with the start/stop button. During treatment, the MCU generates two inverted 2.4 kHz IF signals F IF, F IF and an audio signal F audio, and decodes the stored MP3 format songs into audio digital signals, which are then amplified by a D/A converter amplifier. After that, send it to the headphones or speakers.
The FM output module is composed of frequency modulation, amplification, output dose adjustment, output transformer, and electrode pads. The two-way inverted intermediate frequency signal and one audio signal are frequency-modulated, and after the frequency-modulated signal is amplified, the output pulse voltage is isolated by the output transformer, and the electrode is symmetrically covered to the treatment part of the human body, and the human body perceives the fluctuation with the music. Current stimulation. Through the output dose adjustment, it can meet the requirements of the sensing current when it meets different treatment parts of the human body and the dryness of the skin.
The power module provides 15 V, 5 V, 3.3 V system operating voltage. When the USB port of the therapy device is plugged into the USB interface of the computer, the MCU performs the U disk function, and the USB port of the computer provides +5 V power. During treatment, the power supply of the therapeutic device is generated by voltage conversion, rectification, voltage regulation and filtering of a 220 V AC power supply.
3 hardware system design 3.1 MCU introductionThe embedded device AT89C51SNDIC integrates CPU, MP3 decoder, USB controller and other devices into one. AT89C51SNDIC not only has the control function of 51 series MCU, but also can be extended to MP3 and U disk, using PLCC package, its internal structure block diagram is shown in Figure 2.
The P0, P1, and P3 ports of the AT89C51SNDIC are compatible with the 5l series MCUs, and the 8-bit P4 port and the 4-bit P5 port are added. Clock circuit and reset circuit connection method and 51 series single chip microcomputer.
The first time you use the device, you need to download the USB driver and user program separately. In the 64 KB ROM of the AT89C51SNDIC, the address FOOOH-FFFFH has assimilated the 4K byte Boot Loader code. When shipped from the factory, the BLJB position is set to 1, so that the Boot Loader code is automatically executed after power-on, waiting for the U disk driver or user program object code to be downloaded from the USB interface. After the download is completed, the BIJJB position should be set to 0 in the download software, and the user program should be automatically executed again. If you still need to modify the user program, you can set the ISP pin low. After the power-on reset, the boot loader code is automatically booted and waits for the user program to be updated. Restart the user program and set the ISP pin high.
3.2 Signal Generation and Control ModuleThe circuit block diagram of the signal generation and control module is shown in Figure 3. In order to realize MP3 and U disk functions, AT89C51SNDIC MCU needs to connect a NAND-Flash mass memory. Here, 16 MB K9F2808U0C is selected, its data line I/00~I/07 is connected to P0 port, and the control line is connected to P5 port. The MP3 audio decodes the output signal, and the DOUT, DLCK, DSEL, and SCLK pins of the MCU are connected to the D/A converter CS4330, and are amplified, and output to the earphone to listen to the song played by the MP3. The LCD screen is connected to the P2 port of the MCU, and cooperates with the keyboard to display the working state of the current therapeutic device. There are 4 buttons on the keyboard, and the “Volume/Song/Timer†function button is connected to the P1.0 pin, which is connected to the “next†button of the P1.1 pin and the “previ-OHS†connected to the P1.2 pin. The “key†is used to realize the function of volume adjustment, song selection, treatment timing, etc.; and the “start/stop†button is connected to the P1.3 pin.
The P3.3 pin of the AT89C51SNDIC microcontroller is used to detect whether the U disk or MP3 player is currently being used. If the USB lead of the therapy device is connected to the USB port of the computer, the P3.3 pin detects a high level and executes the U disk program. At this time, the working power of the MCU comes from the USB interface; otherwise, the P3.3 pin When a low level is detected, the MP3 program is executed. The intermediate frequency signal F intermediate frequency, F intermediate frequency and audio signal F audio are respectively connected to the P4.4, P4.5 and DOUT pins of the AT89C5lSN-DlC microcontroller.
3.3 FM output moduleThe schematic diagram of the FM output module circuit is shown in Figure 4. The audio signal F audio is separately modulated with the intermediate frequency signal F intermediate frequency and the intermediate frequency, and two modulated waveforms of opposite phases are generated, which are amplified by 9013, 8050, D880Y and sent to the two input ends of the transformer. The intermediate tap voltage of the transformer can be adjusted by the dose adjustment circuit connected to the mA meter. The 47 kΩ potentiometer is the dose-adjusting potentiometer. When the down-regulation is performed, the current indicated by the milliampere meter becomes smaller, and vice versa. The transformer isolated output voltage changes synchronously with the input voltage. The output voltage is in contact with the human body through the electrode sheet to generate a sensing current in the human body. The body's perceived current is different depending on the location of the physiotherapy and the degree of dryness and wetness of the skin. The physiotherapy needs to adjust the potentiometer to make the physiotherapy feel comfortable.
The operating voltages required for the therapy device are 3.3 V, 5 V, and 15 V from the power module. The principle is shown in Figure 5. 3.3 V voltage can be supplied to the embedded device AT89C51SNDIC; 5 V voltage can be supplied to the FM and amplifier circuits; 15 V voltage can be supplied to the output dose adjustment circuit. Among them, the 5 V voltage regulator uses 78L05, and the 3.3 V voltage regulator uses LDll17S33. When using the U disk function, the USB port of the therapy device is plugged into the USB port of the computer, and the AC power of 220 V is not connected. The working voltage of the MCU is provided by the USB interface.
In conjunction with the hardware circuit function, the system software design flow is shown in Figure 6; the keyboard interrupt service program flow is shown in Figure 7.
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