1 Introduction
DC stabilized power supply is one of the commonly used equipments in electronic technology, and is widely used in teaching, scientific research and other fields. The traditional multi-function DC stabilized power supply has the functions of simple function, difficulty in control, low reliability, large interference, low precision, large volume and high complexity. There are many varieties of ordinary DC regulated power supplies. However, the following problems exist: The output voltage is adjusted by coarse adjustment (band switching) and fine adjustment (potentiometer). Thus, when the output voltage needs to be accurately output, or needs to be changed within a small range (such as 1.02~1.03V), the difficulty is greater. In addition, as the use time increases, band switches and potentiometers are inevitably in poor contact, which has an effect on the output. The current is often limited or blocked by hardware, and the circuit configuration is complicated and the voltage regulation accuracy is not high. This paper designs an intelligent high-precision simple DC power supply with single-chip microcomputer as the core, which overcomes the shortcomings of the traditional DC voltage source and has high application value.
2 system hardware design
2.1 Overall structure of the system
This system is based on AT89S51 single-chip microcomputer as the core controller. It has a voltage-presettable, step-adjustable, output voltage signal and preset voltage signal can be displayed simultaneously. The hardware principle block diagram is shown in Figure 1. The system consists of eight parts: AT889S51 control circuit, keyboard circuit, power supply circuit, D/A circuit, power amplifier circuit, short circuit protection and alarm circuit, voltage regulation output circuit and LED display circuit. The system controls the rise and fall of the preset voltage through the three buttons “switchâ€, “+†and “-â€, and displays it through the digital tube. The AT89S51 MCU sends the corresponding digital signal, and the output current after D/A conversion is finally stabilized by the integrated operational amplifier LM358 conversion, triode amplification, and RC network filtering. At the same time, the output voltage is displayed by the LED digital tube; the measured value is measured by a digital voltmeter.
There are two types of noise canceling headphones, active noise reduction and passive noise reduction.
The active noise reduction function is to generate a reverse sound wave equal to the external noise through the noise reduction system, and neutralize the noise, thereby achieving the effect of noise reduction. Active noise canceling headphones with noise-reducing circuits that compete with external noise. Most of them use a large head-mounted design, which can be used to block external noise by using earplugs and earphone casings, and to perform the first round of sound insulation. There is plenty of room to install active noise reduction circuits and power supplies.
Passive noise canceling headphones mainly form an enclosed space by surrounding the ear, or use soundproof materials such as silicone earplugs to block external noise. Since the noise is not processed by the noise reduction circuit chip, generally only high frequency noise is blocked, and the noise reduction effect on the low frequency noise is not obvious.
Application:
1: Business people, because of frequent business trips, especially those who travel between different cities every day, they must hate the noise in the cabin. If there is a noise-cancelling earphone, they will be able to stay away from these noises. Relax by enjoying the music.
2: The office staff also need a pair of noise canceling headphones. Sometimes when thinking about planning, listening to the sound of central air conditioning is particularly annoying, and if there are colleagues around at this time, it is even more annoying. At this time, you may wear a pair of noise-cancelling headphones to expand your thinking in music.
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