Electronic Firecrackers: Traditional Chinese Circuit Design Guide

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electronic firecrackersFirecrackers are a symbol of auspiciousness. During festivals and happy days, the sound of firecrackers is deafening, and colorful sparks fly all over the sky, giving people joy and encouragement.However, firecrackers not only pollute the environment, but also cause various injuries and fire accidents, bringing unexpected economic losses to the country and people. In order to solve the shortcomings of traditional firecrackers and celebrate people's festivals, this article introduces a method of making electronic firecrackers for the reference and development of enthusiasts and manufacturers.Electronic firecrackers can not only emit simulated sounds like ordinary firecrackers, but can also emit flashes of light along with the sound, making it look like the real thing. Electronic firecrackers are pollution-free, will not cause disability or fire accidents, can be reused, and can greatly reduce economic expenses.1． How the circuit worksThe circuit of the electronic firecracker is shown in Figure 53-1. It is composed of power supply, sound generation, flash and transmission. Figure 53-1In the picture, BG1 and BG2 form a self-excited multivibrator to generate short pulses, which are amplified by the BG3 and BG4 composite tubes to make the loudspeaker emit a loud sound to replace the sound of firecrackers.BG5, step-up transformers B1, B2 and flash tube FT form a flash circuit, which emits corresponding flashes in conjunction with the sound, making the electronic firecrackers more realistic.The flash circuit is composed of oscillation boost, rectifier charging, voltage indication, pulse pulse and flash tube.Transistor BG5, feedback resistor R6, polyester capacitor C4 and oscillation boost transformer B1 form an oscillation boost circuit. Its function is to convert 6V DC low-voltage power into AC high-voltage power.After the power is turned on, triode BG5 starts to oscillate quickly, and the collector current increases, causing the magnetic core of transformer B1 to gradually become saturated. Transistor BG5 is cut off due to the interruption of the base current, and the magnetic flux of the core attenuates. Such repeated cycles will produce self-excited oscillation, causing the transformer to output an AC high voltage of more than 300V on the secondary side after boosting. Since the oscillation frequency is in the audio range, a weak "squeaking" sound can be heard from low to high.The rectifier charging circuit is a constant voltage circuit, and its function is to flash continuously. The bridge full-wave rectifier circuit is used to charge the capacitor C5 so as to minimize the second flash interval.Transistors BG6, BG7, bridge rectifiers D1~D4 and electrolytic capacitor C5 form a rectifier constant voltage circuit. After the power is turned on, the BG5 tube starts to oscillate, but the charging voltage on C5 cannot make the neon bulb NL glow. Only when the voltage at both ends of C5 is charged to 250V, the NL can be turned on, causing BG7 and BG6 to be turned on and BG5 to be turned off. The oscillation circuit stops oscillating; when the DC high voltage is lower than 250V with the discharge of C5, the neon bulb NL is turned off, BG7 and BG6 are cut off, BG5 automatically resumes oscillation, and the DC high voltage rebounds quickly until the neon bulb NL is turned on again. In this way, the DC high voltage is automatically maintained at a constant value over and over again. The essence of the constant voltage circuit is to install an automatic switch at the emitter junction of the oscillation tube BG5.Capacitor Cn], voltage dividing resistor Rn, trigger transformer Bz, trigger switch K2 and flash tube FT form a pulse trigger circuit. The flash tube is a cold cathode discharge tube. A metal cathode and a metal anode are inserted into both ends of the straight tube. A trigger electrode is wound around the outside of the glass tube near the cathode. The outer surface of the glass tube is coated with a conductive layer of tin tetrachloride. The closed glass tube is filled with xenon, an inert gas with high luminous intensity. Under the action of high-voltage electricity, xenon atoms lose electrons and become positive ions. The electrons detached from the atoms gain energy, making the gas in the tube ionized. The ions move within the electric field, causing the gas in the tube to "conduct". In this way, the introduction of external charges between the cathode and the anode causes the electrons and ions to recombine, causing energy to be released in the form of light and causing the gas to discharge. When xenon arc discharges, there is an instant strong flash.While the rectifier diode charges the capacitor C5, it passes through the resistor R. Charging the capacitor Cn, when K2 is turned on, a high voltage of 8~10kv is induced in the secondary of the trigger transformer B2 to trigger the flash tube, ionizing and conducting the xenon in the flash tube; the energy stored in the capacitor C5 is input into the tube through the cathode and anode, causing the xenon to discharge and emit dazzling white light.The one-way thyristor SCR, resistor R5, and capacitor C3 are delay switching circuits. Because after the flash circuit is powered on, it takes a few seconds for the capacitor C5 to charge to a constant voltage value. If the motor M rotates as soon as the power is turned on, the resonant circuit will self-oscillate, and the speaker will make a sound, which will be out of sync with the flash, and the simultaneous sound and light effect will be lost. Now the triggering conduction delay time of the silicon controlled SCR is equal to the time for C5 to charge to a stable voltage. Then the sound and light are simultaneously generated and the motor M rotates accordingly, which can drive the series gun to "ignite", giving people a realistic feeling.Capacitor C6 and resistor R8, C7 and R9, C8 and R10...C. and Rn are set to provide the trigger voltage to the primary of transformer B2 in time. If only one channel of C and R is set, continuous flash cannot be achieved, because it takes a certain period of time for C to charge to the voltage required for triggering after being discharged.The number of C and R voltage dividing circuits is determined by the number of series cannons. In order to reduce the number of C and R voltage dividing circuits, the series cannons can be made into a ring shape.2. Component selection and debuggingB1 is a flash lamp step-up transformer. It uses an E-type magnetic core with a cross-sectional area of 6×5.5mm2. It is first wound with φ0.29mm high-strength enameled wire 15 times as the collector winding. It is padded with a layer of insulating paper, and then wound 15 times with φ0.29mm high-strength enameled wire as the base winding. It is padded with two layers of insulating paper, and then wound 2000 times with φ0.08mm high-strength enameled wire as the boost winding. When winding, a frame as shown in (a) in Figure 53-2 needs to be made, and a magnetic core with a diameter of 4mm and a length of 12mm needs to be inserted into the frame.B2 is the flash trigger transformer, which can use a φ2.5mm, 22mm long magnetic core. The primary is wound with φ0.25 …

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