Shulou(Shulou.com)11/24 Report--

The fifth day of the first lunar month, also known as "broken five", folklore this day is the birthday of the god of wealth, people set off firecrackers to meet the god of wealth on this day, in order to make a lot of money.

The sound of firecrackers greets the God of Wealth: I have cracked the custom of using firecrackers to ward off evil spirits and welcome auspiciousness in our country has a long history:

At the end of the Spring and Autumn period, Fan Li said, "Burning pot firecrackers on New year's Eve and looking at the fire color of the silkworms in the field are both good luck for peace at night."

In the Western Han Dynasty, Dongfang Shuo also recorded the story of "firecrackers driving mountains" in the Book of Divine Yijing.

During the Northern and Southern dynasties, it was recorded in the Chronicle of Jing Chu compiled by Liang Zongyi of the Southern and Northern dynasties: "the first day of the first month is also the day of the three Yuan." the Spring and Autumn period is called the end of the month. The chicken crow rises before the firecrackers in front of the court, in order to ward off the mountain shame evil spirits. "

There is a poem by Liu Yuxi in the Tang Dynasty: "Old Jiao comes out of Zhaotan, firecrackers frighten mountain ghosts."

These records show that since the Spring and Autumn period, there have been "firecrackers" that burst when bamboo burns, and people use firecrackers to ward off evil spirits and welcome auspiciousness.

The early "firecrackers" in the courtyard chart used the principle of thermal expansion of air. There are hollow joints in the bamboo branches, and the air in the bamboo cavity expands when it burns, so that the bamboo joints will suddenly burst and make a sound, so as to achieve the effect of "explosion".

Gunpowder: I'm burning.

Children put paper cannon pictures to the Song Dynasty, due to the invention of gunpowder, gradually appeared firecrackers with gunpowder as raw materials. In the Song Dynasty, "Huiji Zhi" Volume 13 recorded: "New Year's Eve firecrackers heard each other, or sulfur was used as explosive, the sound was especially severe, called firecrackers." it can be seen that firecrackers were used in New Year's Eve in the Song Dynasty.

In the Book of Wulin Old stories of the Zhou Dynasty in the Southern Song Dynasty, it is recorded in the article: "as for firecrackers, there are different kinds of characters such as fruit characters." and the screen entered by the temple chief painted Zhong Kui to catch ghosts and so on. And the hidden medicine line, more than a hundred in a row "," is to connect a single firecracker together, that is, the later firecrackers.

Firecracker structure diagram the basic principle of firecracker explosion is the chemical reaction of gunpowder. Roll gunpowder and oxidizer in the middle with a paper roll, insert a lead at the top, and seal the bottom tightly with soil or other binder. We learned the chemical equation of gunpowder burning in middle school:

Signor2KNO3C = K2S+3CO2 ↑ + N2 ↑

When the fuse is ignited, the gunpowder burns violently in the sealed paper tube and produces a large amount of gas, which expands violently, breaking the paper tube from the middle, and the firecrackers make an explosion.

Fireworks: OK, take off

Colorful fireworks in addition to firecrackers, people also made fireworks. Zhao Mengfu in the Yuan Dynasty had a poem saying: "one after another is as brilliant as a star", and the invention of fireworks adds some color to the festival.

Fireworks structure diagram fireworks structure is divided into two parts, one is the propulsion part, and the other is the effect part, namely fireworks projectile. The propulsion part also uses the principle of gunpowder combustion, but the propellant is wrapped by a solid paper shell, and the gas produced by the gunpowder combustion can not burst the paper shell, but can only be ejected from the space reserved at the end, thus pushing the fireworks projectile into the air. The fireworks bomb in addition to the explosion of gunpowder, but also added many compounds, such as sodium salt, barium salt, the use of flame color reaction to produce a variety of colors.

However, because of the safety and environmental problems caused by setting off firecrackers, a ban on whipping has been implemented in many places. Therefore, people have invented many substitutes for firecrackers one after another.

Such as exploding balloons.

The car rolls balloons to simulate firecrackers, such as dancing whips. We have introduced the principle of dancing whips in the past (the portal pokes here). In a 2002 PRL article, the researchers also analyzed the causes of whip sonic booms, which showed that the scabbard could reach a speed of Mach 2 (2 times the speed of sound). According to the author's calculation, the speed of the tip can reach more than 30 times the initial speed of the whip.

Whip sheath produces shock wave source: Smarter Every Day

Whipping instead of firecrackers electronic salute: the imitation show of sound and electricity at present there is a more popular alternative to firecrackers is electronic salute and electronic firecrackers. First of all, let's take a look at this big guy-- the electronic salute.

The principle of the electronic salute is that the gas explosion produces the sound of the salute. The electronic salute uses thick-walled and seamless steel tubes to make the barrel.

Electronic salute structure diagram people use a circuit to control the solenoid valve, fill the gun barrel with oxygen and natural gas in proportion, ignite the mixed gas through the ignition device, and make the gas explode to make a salute sound.

After the electronic salute schematic diagram, let's take a look at the little guy-- the electronic firecracker.

Electronic firecracker physical map the so-called electronic firecracker is through the circuit control to achieve the real firecracker explosion of light, sound, smoke and other phenomena. Let's take a closer look at how it works.

For electronic firecrackers, the most important thing is to simulate the sound of firecrackers explosion. Now there are generally two ways to implement it.

The first method is to use the loudspeaker to simulate, the principle is to use the circuit to play the pre-recorded high-quality firecracker explosion sound. For example, the ISD1820 single-segment voice recording and playback chip is used in the circuit shown below to record the sound of firecracker explosions.

The second method of electronic firecracker audio generation circuit schematic is to use the circuit to achieve high-voltage breakdown of air to produce explosive sound.

Single-tube self-excited boost circuit diagram A common form of life is a 18650 lithium battery, which can provide a voltage of about 3.7 V. Using a single-tube self-excited boost circuit as a high-voltage generating circuit, the 3.7V voltage can be raised to more than ten kilovolts to charge the capacitor. The resistor R1 and the diode D1 constitute the base voltage biasing circuit, which makes the signal generated by the Triode Q1 collector coil feedback to the base coil to produce self-excited oscillation, so that the secondary coil can get several times the voltage. High pressure penetrates the air to form a harsh sound, thus simulating the sound effect of a firecracker explosion.

In addition to the simulation of firecracker explosion sound, electronic firecrackers can simulate explosion sparks by using LED circuit. The explosion sparks of firecrackers are always accompanied by the explosion sound, and the flash accompanied by the explosion sound can be simulated by using the voice-controlled flash circuit.

Voice-controlled flash circuit two transistors Q2 and Q3 in the voice-controlled flash circuit form a two-stage direct coupling amplifier. Select the appropriate R3, R4, when there is no sound change outside the transistor Q2 is in the critical saturation state, resulting in the Triode Q3 in the cut-off state, then there is no current through the three LED and keep the extinguished state.

When the microphone MIC receives the acoustic signal, the audio signal is converted into a current signal that flows into the base of the transistor Q2, which causes Q2 to withdraw from the saturated state and the collector voltage of Q2 to rise. In this way, the transistor Q3 will turn on, making the three LED light up. If the input audio signal is weak enough to make Q2 out of the saturated state, the LED remains off, and only when the strong signal is input, the diode lights up and emits light, so the diode can flicker and glow with the fluctuation of the ambient sound signal.

Reviewing the past and present life of firecrackers, from early "firecrackers" to firecrackers that used gunpowder, and now substitutes such as electronic firecrackers and electronic salutes, what is constantly changing is the way of sound. What remains unchanged is that people use sound to express their wish to bid farewell to the old and expel evil spirits and welcome good luck. With the development of science and technology, firecrackers as an entity may continue to evolve in the future, but it will not change as a carrier of people's will to pursue a better future.

References:

Wang Jicheng, he Zhicheng, Cai Jingyi, Zhu Jian. A new type of environmental protection electronic firecrackers [J]. Modern computer, 2020 (12): 155157.

[2] Wang Yuanlan. Design and manufacture of electronic gas salute [J]. Shandong Meteorology, 1999 (04): 59-60.

Hu Lu, Zhang Ye, Jian Wuzhen, Jiang Xing, Xu Lili, Xu Zhonghui. A novel design of electronic firecrackers [J]. Science and Technology Plaza, 2016 (09): 173,176.

Wei Shuping, Wang Demiao, Jin Hao. Magnetron sputtering metallization of microwave dielectric ceramic resonator [J]. Journal of Materials Science and Engineering, 2016 Ji 34 (05): 689-693.

[5] Li Fuxu. Design and implementation of portable intelligent atomizer [D]. Shanghai University of Applied Technology, 2016.

Zhou Xing, Zhou Chao. Folk custom and law: fireworks and firecrackers as a "China problem" [J]. Journal of Hubei University for nationalities (philosophy and Social Sciences Edition), 2018. 36 (04): 48-58.

This article comes from the official account of Wechat: Institute of Physics, Chinese Academy of Sciences (ID:cas-iop).

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