[Flower carving hands-on] Interesting and fun music visualization series of small projects (17) - fiber optic lamp

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[Flower carving hands-on] Interesting and fun music visualization series of small projects (17) - fiber optic lamp [Copy link]

 

I had the urge to do a series of topics on sound visualization. This topic is a bit difficult and covers a wide range of areas. The related FFT and FHT algorithms are also quite complicated. However, I still plan to start with the simplest one, do some experiments, try various solutions patiently, gradually accumulate some useful music spectrum visualization materials, and strive to form some practical and fun music visualizer projects. This time I purchased 50 meters of optical fiber online, and wanted to try whether it was feasible as a music lamp, but I was still shocked when I received the express delivery, it was too thin and too mini.

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After searching online, I found that optical fiber, or optical fiber (English: Optical fiber), is a fiber made of glass or plastic, which is a light transmission tool that uses the principle of total internal reflection to transmit light in these fibers. The tiny optical fiber is encapsulated in a plastic sheath, allowing it to bend without breaking. Usually, the transmitting device at one end of the optical fiber uses a light-emitting diode or a laser beam to send light pulses into the optical fiber, and the receiving device at the other end of the optical fiber uses a photosensitive component to detect the pulses. The cable containing optical fibers is called an optical cable. Because the transmission loss of information in optical fibers is much lower than the loss of electricity in wires, and because the main raw material for production is silicon, which has a huge reserve and is relatively easy to mine, the price is very cheap, which has prompted optical fibers to be used as long-distance information transmission media. As the price of optical fibers continues to drop, optical fibers are also used for medical and entertainment purposes.

Optical fibers are mainly divided into two categories, graded-index fiber and step-index profile fiber. The refractive index of the former is graded, while the refractive index of the latter is step-index profile. In addition, they are divided into single-mode fiber and multi-mode fiber. In recent years, new photonic crystal fibers have been introduced.

Optical fiber has a double structure, the core part is high refractive index glass, the surface part is low refractive index glass or plastic, light is transmitted in the core, and is constantly totally reflected at the junction of the surface, and is transmitted forward along a zigzag shape. This fiber is slightly thicker than a hair, and it is an amazing technology to have such a thin fiber with a double structure distribution with completely different refractive indices. After years of hard work, scientists from various countries have created the internal attachment method, MCVD method, VAD method, etc., and made ultra-high purity quartz glass. The efficiency of specially made optical fiber in transmitting light has been significantly improved. Now the better optical fiber has a light transmission loss of only 0.2 decibels per kilometer; that is, after transmitting one kilometer, only 4.5% is lost.

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The sound module uses the more cost-effective MAX4466 sound sensor.

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MAX4466 module features
Power supply voltage: +2.4V to +5.5V (can be directly connected to STM/ARDUNIO/Raspberry Pi and other development boards)
Power supply rejection ratio: 112dBCommon
mode rejection ratio: 126dBAVOL
: 125dB (RL = 100kΩ)Rail-to-rail output
Quiescent supply current: 24μAGain bandwidth
: 600kHzDimensions
: 20.8mm x 13.8mm x 7.5mm/0.8 x 0.5 x 0.3inch

The module includes ferrites on both the Vcc and ground leads to minimize power supply noise. If used with an MCU, it is best to use the quietest power supply available in the 2.4V – 5.5V range. On an Arduino this is typically a 3.3V supply.

The output is DC coupled. When the output signal is at rest, it will be at Vcc/2. If Vcc is 5V, the output will be 2.5V. If the output needs to be AC coupled, a 100uF capacitor can be added between the output pin and the input of the circuit it drives.

The small single-turn potentiometer on the back allows you to adjust the gain from 25x to 125x. Turning the potentiometer counter-clockwise increases the gain, while turning it counter-clockwise decreases the gain.

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LED using WS2812B

WS2812B is an intelligent control LED light source that integrates control circuit and RGB chip. The packaging of 5050 components. The internal includes intelligent digital port data latch and signal shaping amplification drive circuit. It also includes a precision internal oscillator and a 12V voltage programmable constant current control part, which effectively ensures that the light color of the pixel point is highly consistent. The data transmission protocol adopts a single NZR communication method. After the pixel is powered on and reset, the DIN port receives data from the controller, the first pixel collects the initial 24 bits of data, and then sends it to the internal data latch, and the other data is sent to the next cascade pixel through the DO port by the internal signal shaping amplification circuit for shaping. After the transmission of each pixel, the signal is reduced by 24 bits. The pixel adopts automatic shaping transmission technology, so that the number of pixel cascades is not limited by signal transmission, but only depends on the speed of signal transmission. The reset time is >280μs, and it will not cause false reset when interrupted, supporting lower frequency and low-cost single-chip microcomputers. The refresh frequency is updated to 2kHz, the picture frequency is low, and the high-definition camera is flicker-free, which improves the excellent display effect. LED has the advantages of low driving voltage, environmental protection and energy saving, high brightness, large scattering angle, good consistency, low power and long life. More and more control chips are integrated on LEDs with simple circuits, small size and easy installation.

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WS2812B uses four-bit module

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Four-bit module electrical schematic

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Module pin
VCC---This pin needs to be connected to a 5V-7V DC power supply. If the voltage is too high (7V), the LED will burn out. If the voltage is too low (5V), the brightness will be too low or even the LED will not work.

GND---Common pin, grounded, that is, connected to the negative pole of the power supply.

IN---The data of the microcontroller (or another WS2812) is transmitted to the LED from this pin.

OUT---The data is output from here to the next level WS2812. If this WS2812 is the last level, this pin can be left floating.

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The optical fiber I got the first time was too thin, so I planned to cut it into 10 cm segments, with a total length of 50 meters, which would make 500 segments.

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Principle of optical fiber

Optical fiber is a cylindrical dielectric waveguide that uses the principle of total internal reflection to conduct light. The structure of an optical fiber is roughly divided into an inner core part and an outer cladding part. In order to confine the light signal to the core, the refractive index of the cladding must be smaller than the refractive index of the core. The refractive index of a graded-index fiber changes slowly, gradually decreasing from the axis to the cladding; while the refractive index of a step-index profile fiber changes sharply in the core-cladding boundary area. The picture shows various optical fibers.

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Two concepts of optical fiber
1. Refractive
index The refractive index can be used to calculate the speed of light in a substance. In a vacuum and in outer space, the speed of light propagation is the fastest, about 300 million meters per second. The refractive index of a substance is the speed of light in a vacuum divided by the speed of light propagation in the substance. Therefore, by definition, the refractive index of a vacuum is 1. The larger the refractive index, the slower the light propagation speed. Usually, the refractive index of the core of the optical fiber is 1.48, and the refractive index of the cladding is 1.46. Therefore, the speed of optical fiber transmission signals is roughly about 200 million meters per second. Telephone signals, transmitted through optical fiber, from New York to Sydney, a distance of about 12,000 kilometers, will have a minimum delay of 0.06 seconds.

2. Total internal reflection
The laser bounces off the inside of an acrylic stick, showing total internal reflection of the light.
When light moving through a denser medium is incident on the core-cladding boundary at a large angle, if the angle of incidence (the angle between the light and the normal to the boundary surface) is greater than the critical angle, the light will be completely reflected back. Optical fiber uses this effect to confine the transmission of light to the core. Light propagating inside the optical fiber will be reflected back and forth by the boundary. Since the angle at which the light is incident on the boundary must be greater than the critical angle, only light that enters the optical fiber within a certain angle range can pass through the entire optical fiber without leakage loss. This angle range is called the acceptance cone of the optical fiber, which is a function of the difference between the core refractive index and the cladding refractive index of the optical fiber.

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500 cut optical fibers

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Find two bottle caps to make the base

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The ends of the optical fiber should be cut flush

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Fixed four-digit LED module

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Mini fiber optic light

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[Flower carving DIY] Interesting and fun music visualization series of small projects (17) - Fiber optic lamp
project program 1: Simple test breathing light

/*
  【花雕动手做】有趣好玩的音乐可视化系列小项目（17）--光导纤维灯
  项目程序之一：简单测试的呼吸灯
*/

#include <Adafruit_NeoPixel.h>
#define PIN 6
#define MAX_LED 4
#define ADD true
#define SUB false

int val = 0;
boolean stat = ADD;

Adafruit_NeoPixel strip = Adafruit_NeoPixel( MAX_LED, PIN, NEO_RGB + NEO_KHZ800 );

void setup() {
  strip.begin();
  strip.show();
}

void loop() {
  uint32_t color = strip.Color(val, val, val);
  strip.setPixelColor(0, color);

  if (val >= 235)
    stat = SUB;
  if (val <= 0)
    stat = ADD;

  strip.show();
  delay(15);
  if (stat == SUB) val --;
  else if (stat == ADD) val++;
}

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Experimental scene diagram Dynamic diagram

点击上图查看Gif动图

lugl4313820

This project is quite creative. Can we control each optical fiber individually to display different colors? . . .