Design of intelligent pedometer based on single chip microcomputer
1 Introduction
In today's society, with the development of the economy, people's living standards have improved, and more and more obese people have caused more and more diseases. Therefore, people are paying more and more attention to health problems, and exercising is to let The most effective way to be healthy. Therefore, the pedometer has emerged as the times require, and it has become a popular trend. When walking, by stretching the muscles, the blood's resistance during the flow decreases, and the blood pressure drops and stabilizes. People who walk often rarely suffer from high blood pressure or low blood pressure. Persistence in walking can reduce the fatty substances attached to the blood vessels, reduce weight, and gradually reduce the load on the heart. The pedometer based on the single chip microcomputer has the advantages of accuracy, reliability, stability and convenience, and has been accepted by most people. Through the pedometer, people can know how many steps they have run and master their exercise in real time.
2 overall design
The pedometer consists of an oscillating circuit, a reset circuit, a display circuit, and a button circuit, and is powered by a battery. The system structure diagram is shown in Figure 1.
Figure 1 System structure diagram
3 hardware design
3.1 Oscillation circuit
The AT89C51 MCU has an oscillating circuit composed of an inverting amplifier. The oscillating circuit is a guarantee for the normal operation of the MCU system. If the oscillator does not vibrate, the system will not work. If the oscillator is running irregularly, the time error will occur when the system executes the program. This will be obvious in the communication, and the circuit will not be able to communicate.
It consists of a crystal and two ceramic capacitors. The two capacitors in the clock circuit are used as compensation, making the crystal easier to oscillate and the frequency more stable. as shown in picture 2.
Figure 2 Oscillation circuit
3.2 reset circuit
In order to ensure stable and reliable operation of the circuit in the microcomputer system, the reset circuit is an indispensable part. The first function of the reset circuit is the power-on reset. Generally, the normal operation of the microcomputer circuit requires 5V ± 5% of the power supply, which is 4.75~5.25V. Since the microcomputer circuit is a sequential digital circuit, it needs a stable clock signal. Therefore, when the power supply is powered up, the reset signal is removed only when VCC exceeds 4.75V below 5.25V and the crystal oscillator operates stably. The microcomputer circuit starts normal. jobs. The reset of the system adopts the form of power-on reset. During the power-on process, the microcontroller reset pin ensures that the microcontroller is reset at a high level of more than 10ms. As shown in Figure 3.
Figure 3 reset circuit
3.3 display circuit
This design uses a 4-digit LED common cathode digital tube display as the display interface of the system, as shown in Figure 4. The commonly used LED display is 8 or 7 segments (8 segments have a decimal point "dp" segment than 7 segments). Each segment corresponds to a light emitting diode. This type of display consists of a common anode and a common cathode. As shown in Figure 4. The cathodes of the LEDs of the common cathode LED display are connected together, usually sub-cathode grounded. When the anode of a certain LED is at a high level, the LED is lit and the corresponding segment is realized. In order for the LED display to display different symbols and numbers, it is necessary to illuminate the different segments of the LEDs, thus providing code for the LED display, because these codes can cause the corresponding segments of the LED to illuminate, thereby displaying different fonts, so The code is called a segment code (or a font code). The 7-segment LED is added with a decimal point for a total of 8 segments. Therefore, the segment code supplied to the LED display is exactly 1B.
Figure 4 display connection circuit
3.4 button circuit
This design is to replace the vibration generated by the person walking in the form of a button. Each time the button is pressed, it means that the person walks one step. The circuit is shown in Figure 5.
Figure 5 button circuit
3.5 ADXL202 Sensor Circuit
The ADXL022 sensor module circuit is shown in Figure 6.
Figure 6 ADXL202 sensor module circuit
4 system software
The pace begins and the internal procedures are in place. When the person walks one step, the sensor detects the peak value, and after four kinds of circuits, it is displayed by the display, and then one step is taken, and the accumulator is incremented by one, thereby adding one step by step and displaying by the display. The microcontroller reset system generates an external interrupt and the display is set to zero. The system flow chart is shown in Figure 7.
Figure 7 system flow chart
5 software simulation
In the system, the button K1 in the button circuit is connected with the P4.4 of the single chip microcomputer, and the dedicated button circuit generates an oscillating circuit, and the electric signal is converted to the microcontroller through the circuit, and the microcontroller will represent the digital quantity of the current step according to 10 After processing, it is displayed by visual LED. When the button is pressed once, the display shows 1, and how many times it is displayed. The pedometer simulation effect diagram is shown in Figure 8.
Figure 8 simulation renderings
6 Conclusion
The main design of this paper includes the microcontroller, display components, input components and real-time clock. In the entire design system, fully grasp the working principle of each module circuit, design the hardware circuit and software program, and finally simulate.
TFT (Thin Film Transistor) is a thin film field effect transistor. The so-called thin film transistor means that each liquid crystal pixel on the Liquid Crystal Display is driven by a thin film transistor integrated behind it. This can Display Screen information at high speed, high brightness, and high contrast. TFT is an active matrix liquid crystal display.
The TFT-LCD liquid crystal display is a thin film transistor type liquid crystal display, also known as "true color" (TFT). TFT liquid crystal has a semiconductor switch for each pixel, and each pixel can be directly controlled by dot pulses, so each node is relatively independent and can be continuously controlled, which not only improves the response speed of the display, but also can be accurately controlled Display color gradation, so the color of TFT liquid crystal is more real.
In the fierce competition among many flat panel displays, why TFT-LCD can stand out and become the next-generation mainstream display is by no means accidental, it is the inevitable development of human technology and thinking mode. The liquid crystal has avoided the difficult light-emitting problem successively, and the light-emitting display device is decomposed into two parts by using the excellent characteristics of the liquid crystal as a light valve, namely the light source and the control of the light source. As a light source, brilliant results have been achieved in terms of luminous efficiency, full color, and life, and they are still being deepened. Since the invention of LCD, the backlight has been continuously improved, from monochrome to color, from thick to thin, from side fluorescent lamp type to flat fluorescent lamp type. The latest achievements in luminous light sources will provide new backlight sources for LCDs. With the advancement of light source technology, newer and better light sources will appear and be applied to LCDs. The rest is the control of the light source, the technology and process of the semiconductor large-scale integrated circuit are transplanted, the thin film transistor (TFT) production process has been successfully developed, the matrix addressing control of the liquid crystal light valve is realized, and the light of the liquid crystal display is solved. The cooperation of the valve and the controller enables the advantages of the liquid crystal display to be realized.
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ESEN Optoelectronics Technology Co., Ltd, , https://www.esenlcd.com