Fireworks are set off during festivals and ceremonies. Its gorgeous and colorful patterns, warm explosion sounds and joyful atmosphere can leave a good impression on people, but there are certain hidden dangers of smoke pollution and explosion hazards. This circuit can simulate a firework display device to achieve the effect of both sound and shape, and bring a relaxed and happy atmosphere to people in a safe and environment-friendly environment. The circuit structure is novel, there are not many components, and the debugging is easy, so it is suitable for self-made. It can also be used as an open design reference for engineering and technical personnel of small enterprises. The device can be used in family celebrations, friends gatherings, gala parties, children's toys and some interesting places.
1. The working principle of the circuit
The circuit principle is shown in the figure.
The device is made by adopting the circuit, which is composed of two parts: a light-emitting circuit for simulating the color of the firework and a sounding circuit for simulating the explosion sound of the firework. In the figure, IC1 is the time base integrated circuit 555, which constitutes a square wave generator, and the square wave oscillation signal is sent out in two ways. Send all the way to the decimal integrated circuit counter IC3 (CD4017) as a trigger signal to make it count. The result of each count (when one of Q0~Q6 of CD4017 is "1") is respectively transmitted to the control terminal of the corresponding integrated electrical bidirectional analog switch CD4066 by diodes D1~D12, so that three CD4066 (1), ( 2), (3) or conduction alone or in combination. In this way, the square wave signal of IC1 can drive the corresponding triodes T1~T3 to conduct in saturation through the analog switch, and light up the
corresponding light-emitting diodes LED1~LED3.
When the square wave oscillating signal drives the triode, it must first pass through a differential circuit composed of a resistor Rb and a capacitor Cb. According to the characteristics of the differential circuit, the subsequent triode is turned on after the rising edge of the square wave, and then the voltage at point Vb is The exponential law rate is reduced to 0, so the LED driven by the triode also has a short process from suddenly lighting up to gradually dimming. The length of this process can be adjusted by the value (time constant) of Rb and Cb.
The output of the CD4017 counter and the on-state of the CD4066 analog switch, that is, the lighting of the light-emitting diode LED, are shown in the attached table. When the Q7 terminal of CD4017 is "1", the counter is reset. As the oscillating signal of the 555 integrated circuit IC1 is continuously generated, the phenomena listed in the attached table appear cyclically, and the 7 colors (single color or three primary colors) emitted by the light-emitting diodes also circulate continuously, and the lighting process of each light color There will be a feeling similar to fireworks flickering and then going out quickly.
Transistors T1, T2, and T3 are all driven by RC differential circuits. If the triode T1 is changed to an RC integrating circuit (the positions of R and C in the circuit are interchanged), the red LED can have a delay in the ignition time. , so that when more than two LEDs are lit, there will be a difference in timing, resulting in an animation-like layering.
Another way to simulate the sound of setting off fireworks is completed by the time-base integrated circuit 555IC2, which is also an oscillator, but the potentiometer connected to pin 4 of the reset terminal is composed of the square wave signal output by IC1 through R1 and C1 After the differential circuit is generated, that is, from the rising edge of the square wave and after a period of time, the pin 4 of IC2 can maintain a high level "1" and make it work, and the generated oscillation signal directly drives the speaker and the LED driven by the triode Light up synchronously, making a sound similar to fireworks explosion.
2. Component selection
IC1 and IC2 choose 555 integrated circuits, IC3 counters choose CD4017 and other integrated circuits, integrated circuit bidirectional analog switches can choose CD4066 and other types, LED1 and LED2 can choose ordinary light-emitting diodes, red, green and blue three LEDs should choose φ5 or more Ultra-high brightness light-emitting diodes, and other components can be selected according to the parameters given in the circuit diagram.
3. Production and debugging method
As long as the circuit is installed correctly, it can work normally. Adjusting the potentiometer VR1 can change the oscillation frequency of IC1, so that there is a suitable short pause during each fireworks display. The light-emitting diode LED1 is used to indicate its working status. Adjusting the potentiometer VR2 can change the oscillation frequency of IC2, so that the speaker emits a sound similar to fireworks, and LED2 is used to indicate its working status. These three light-emitting diodes of red, green and blue should be installed together in a triangular shape, so that they can emit light and adjust color. A panel with a firework pattern composed of light-transmitting holes is placed in front of them, and the distance between them can be adjusted in the experiment. In the room where the lights are turned off at night, when the various colored lights when the LEDs are on are projected onto the white paper or the white wall through the panel, it will produce a colorful, starry, and sound-like fireworks effect.