LED digital tube knowledge principle

The LED digital tube is actually composed of seven LEDs in a figure-eight shape, plus eight decimal points. These segments are represented by the letters a, b, c, d, e, f, g, dp, respectively. When a specific segment of the digital tube is applied with a voltage, these specific segments will illuminate to form the 2 8 words that our eyes see.

Such as: display a "2" word, then it should be a bright b bright g bright e bright d bright f no bright c no bright dp not bright. LED digital tubes are generally bright and super bright, and also have different sizes such as 0.5 inch and 1 inch. The display pen of a small-sized digital tube is usually composed of one light-emitting diode, and the large-sized digital tube is composed of two or more light-emitting diodes. Under normal circumstances, the tube voltage drop of a single light-emitting diode is about 1.8V, and the current does not exceed 30 mA.

The anode of the light-emitting diode is connected to a positive-positive digital tube that is connected to the positive pole of the power source, and the cathode of the light-emitting diode is connected to a negative-phase digital tube that is connected to the negative pole of the power source. The numbers and characters displayed by the commonly used LED digital tube are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F.

The structure and working principle of led digital tube

LED segment displays are devices that are packaged together by a plurality of light-emitting diodes to form an "8" shape. The leads are connected internally, and only need to draw their respective strokes and common electrodes. The number of commonly used segments of the led digital tube is generally 7 points plus one decimal point, and the other is similar to the 3-digit "+1" type. There are half digits, 1, 2, 3, 4, 5, 6, 8, 10, etc.., led digital tube is divided into two types according to the different methods of LED connection, common LED and common Yang, understand LED These characteristics are very important for programming, because different types of digital tubes, in addition to their hardware circuits are different, the programming method is different. Figure 2 shows the internal circuits of the common cathode and common anode digital tubes. Their principle of illumination is the same, except that their power supply polarity is different. The colors are red, green, blue, yellow and so on. Led digital tube is widely used in instruments, clocks, stations, home appliances and other occasions. Pay attention to product size, power consumption, brightness, wavelength, etc. when selecting. The following will introduce the internal pin picture of the commonly used LED digital tube. Figure 1 This is a 7-segment LED digital tube with a decimal point of 10 pins. Figure 2 Pin definition

Each stroke is corresponding to a letter indicating that DP is a decimal point.

LED digital tube should be displayed normally, it is necessary to use the drive circuit to drive the various segments of the digital tube, thus showing the number we want, so according to the different driving methods of the LED digital tube, it can be divided into two types: static and dynamic. .

A, static display driver:

Static drives are also called DC drives. Static drive means that each segment of each digital tube is driven by an I/O port of a single-chip microcomputer, or by using a BCD code two-tenth* device*. The advantage of static drive is that the programming is simple, the display brightness is high, and the disadvantage is that it takes up more I/O. For example, if you drive 5 digital tube static display, you need 5×8=40 I/O ports to drive. You need to know that a 89S51 MCU is available. The I/O port is only 32. Therefore, the actual driver must increase the * drive to drive, increasing the complexity of the hardware circuit.

B, dynamic display driver:

The digital tube dynamic display interface is one of the most widely used display modes in the single-chip microcomputer. The dynamic drive is to display the same names of the eight display strokes of all digital tubes "a, b, c, d, e, f, g, dp". The terminals are connected together, and the bit gate control circuit is additionally added for the common pole COM of each digital tube. The bit gates are controlled by independent I/O lines. When the single chip outputs the font code, all the digital tubes are received. The same glyph code, but the digital tube will display the glyph, depending on the control of the microcontroller's semaphore COM terminal circuit, so we only need to open the gating control of the digital tube that needs to be displayed, the bit will display Out of the glyph, there will be no bright digital tube without strobing.

By controlling the COM end of each LED digital tube by means of time-sharing, the digital tubes are controlled to display in turn, which is dynamic driving. In the process of rotating display, the lighting time of each bit digital tube is 1~2ms. Due to the persistence of human vision and the afterglow effect of the LED, although the digital tubes are not lit at the same time, they only need to be scanned. The speed is fast enough, giving the impression that a stable set of display data, no flickering, dynamic display and static display are the same, can save a lot of I / O port, and lower power consumption.

Features

1. LED digital tube uses light-emitting diode as the light-emitting unit, the color has single red, yellow, blue, green, white, and colorful effects. Monochrome, segmented full-color tube can be used to brighten the outline of buildings, roads and river banks. LED digital tubes can be evenly arranged to form a large-area display area, which can display patterns and texts, and can play video files of different formats. Use the computer to flash, animation, text and other documents, or use animation design software to design personalized animation, play a variety of dynamic and discolored graphic effects.

2. It can be placed on the PCB circuit board in a straight line in the order of red, green and blue. It is controlled by a dedicated driver chip to form endless colors and graphics. The shell is made of flame retardant PC plastic, high strength, impact resistance, anti-aging, anti-ultraviolet, dustproof and moisture proof. LED guardrail tube has the advantages of low power consumption, no heat, impact resistance, long life, etc. With the controller, it can realize the effects of water flow, gradual change, jump, chase and so on. If applied to large-area projects, connected to the computer synchronization controller, can also display patterns, animated video equivalent LED digital full-color lamps can form an analog LED display , analog display can provide a variety of full-color effects and dynamic display Image characters can be synchronized with offline control or computer connection; they can display a wide range of full color dynamic effects. The control system is edited by Santai VISS special lighting programming software. The digital tube control pattern is easy to change. Simply copy the edited pattern format file into the CF card, and the digital tube controller can be controlled separately or multiple online. The digital tube installation and arrangement method is arbitrary, suitable for various complex engineering needs. Digital tube, controller and power supply are connected by standard male and female plugs. It is convenient and fast, and has a unique shape design. The new outdoor waterproof structure

Technical Parameters

Specifications: (round, semi-circular, D-shaped); diameter: 30mm, 40mm, 50mm, 80mm, 100mm, 110mm Color: single red, yellow, blue, green, white, colorful; shell color: milky white; performance : Waterproof, dustproof, UV resistant, pressure resistant, crack resistant, high temperature resistant, flame resistant, super impact resistant aging; Protection class: IP65; Operating voltage range: 24V-220V; Working power: 8-12W; Working environment : -40 degrees - +75 degrees. Normal life: >80,000 hours

Application areas:

Mainly used for building walls, advertising signs, high-end DISCO, bars, nightclubs, clubhouse billboards, etc. It is especially suitable for use in billboards, overpasses, rivers, lake guardrails, building contours, etc., which can produce rainbow-like effects. Decorate the outline of the building with a guardrail tube to highlight the effect of beautifully colored buildings. It turns out that it has become a wonderful thing in lighting products, blooming in a dynamic city.

LED digital tube driver

LED digital tube should be displayed normally, it is necessary to use the drive circuit to drive the various segments of the digital tube, thus showing the number we want, so according to the different driving methods of the LED digital tube, it can be divided into two types: static and dynamic. .

Static display driver

Static drives are also called DC drives. Static drive means that each segment code of each digital tube is driven by the I/O port of a single-chip microcomputer, or by decoding with a BCD code binary-decimal decoder. The advantage of static drive is that the programming is simple, the display brightness is high, and the disadvantage is that it occupies more I/O ports. For example, if the static display of 5 digital tubes is driven, 5×8=40 I/O ports are needed to drive. It is necessary to know that a 89S51 MCU is available. The number of I/O ports is only 32:), the actual application must increase the decoding driver to drive, increasing the complexity of the hardware circuit.

Dynamic display driver

The LED digital tube dynamic display interface is one of the most widely used display modes in the single-chip microcomputer. The dynamic drive is to display the eight display strokes of all digital tubes "a, b, c, d, e, f, g, dp" The same name is connected together, and a bit strobe control circuit is added for the common pole COM of each digital tube. The bit strobes are controlled by independent I/O lines. When the single chip outputs the font code, all the digital tubes receive the same The glyph code, but the digital tube will display the glyph, depending on the control of the MCU's bit strobe COM circuit, so we only need to open the gating control of the digital tube that needs to be displayed, this bit will display the glyph. A digital tube that is not strobed will not light up. By controlling the COM end of each digital tube in turn, the digital tubes are controlled to display in turn, which is dynamic driving. During the rotation display process, the lighting time of each digital tube is 1~2ms. Due to the persistence of human vision and the afterglow effect of the LED, although the digital tubes are not lit at the same time, as long as the scanning speed is sufficient Fast, the impression is a stable set of display data, there will be no flickering, the dynamic display is the same as the static display, can save a lot of I / O ports, and lower power consumption.

LED digital tube classification

1. From the control mode: divided into internal control mode (internal MCU, power-on automatic color change) and external control mode (requires external controller to change color). 2, from the change method: divided into fixed color and colorful, full color; fixed color is used to hook outline, full color can be hooked outline, can also form a tube screen display text, video, etc.; Divided from the size: D50, D30, this is the diameter; the length is basically 1 meter (can be customized) from; this needs to be selected according to actual needs. 4, from the internal controllability: there are 1 meter 6 paragraphs, there are 1 meter 8 paragraphs and 1 meter 12 paragraphs, 1 meter 16 paragraphs, 1 meter 32 paragraphs. That is, there are several sections in the 1 meter tube that can be independently controlled; the more the number of 1 meters, the better the effect of making video. If the density is low, or do some chasing effect, you can do 1 meter and 6 segments. 5, from the number of led, there are 1 meter 96 lights, there are 1 meter 144 lights; the more the light the better. Generally, all the colors are made with 144 lamps of 1 meter. 6, from the power supply points, divided into high-voltage power supply (direct 220V power supply) and low-voltage power supply (12v power supply, 220v power supply need to add switching power supply conversion); generally choose low-voltage power supply, relatively reliable and stable, high-voltage power supply is easy to burn. 7, according to the pixel point of one meter 16-segment tube is 1 meter of light tube has 16 pixels. Generally there are 6 digital tubes, 8 digital tubes, 12 digital tubes, 16 digital tubes, 32 digital tubes, etc. There are more than 16 segments. For example, a 6-segment digital tube is generally used on a contour item.

LED full color digital tube effect control system

1. Waterproof LED guardrail tube is generally sealed with hot melt adhesive or silicone at the interface of the outer cover. The internal LED and circuit board are bare. Due to the large temperature difference between day and night, the end of the outer cover and the outer cover are different from thermal expansion and contraction, resulting in hot melt. There is a gap in the rubber or silicone seal. After the rain, rainwater seeps into the interior, causing a short circuit and burning the LED. To solve this problem, it is necessary to fill the internal circuit and LED. It is simple to use a hot melt adhesive or a silicone seal, but the reliability is not as high as that required for outdoor applications.

2, anti-UV LED guardrail tube because of the need to mix light and rain, there will be a cover outside, the material selection of the cover is another means of reducing the cost of non-standard companies, good quality products will use increased UV-resistant materials. Such as GE, Bayer and other materials, and the quality of the LED guardrail tube is a lot of materials mixed with nozzle material, can not talk about anti-UV, the sun is relatively large, less than a month, the cover becomes yellow Therefore, the light-emitting effect is deteriorated, and the light transmittance is also greatly reduced.

3, line loss non-ferrous metal price increase, the use of inferior materials and reduce the wire diameter is a way for some manufacturers to save costs, generally good manufacturers will use more than 1mm wire inside, and the wire material is used in line with the national standard products . If the wire area is not enough or the material has too many impurities, the resistance value is large, and the front guardrail tube and the rear guardrail tube have a large voltage difference. In order for the rear LED to work normally, it is necessary to increase the input voltage. This invisibly increases power consumption, and much of the power is not used to drive the LEDs, but is wasted on the wires and constant current chips. Nowadays, the universal constant current chip has power consumption requirements, and the voltage and power consumption are large. If the power consumption is too large, the heat will not be discharged and the chip will be burned. This is why many LED guardrail tubes are much more damaged in front.

4, heat dissipation general LED guardrail tube cover and base are completely integrated, are plastic materials. When the LEDs are arranged very densely, after the heat balance is applied, the junction temperature of the LEDs is already high, which will cause the life of the LEDs to drastically decrease. The strong LED guardrail tube company will definitely have thermal designers. When designing the guardrail tube cover, it will idea to effectively transfer the heat of the LED and the heat of the constant current chip to the atmosphere. It is a good method to use aluminum on the base. In addition, the PCB should be placed as close as possible to the aluminum base.

5. There are two ways to supply power to the power supply guardrail: 220V high voltage and low voltage below 48V. Direct 220V power supply is a dangerous and uneconomical way. The low voltage method is to use a Capacitor or resistor to reduce the voltage. This approach is first of all a big problem with security; secondly, it is too power-hungry and has great damage to the power grid. The power supply department is firmly opposed. Suddenly, a large number of capacitive loads are added to the line, causing the power supply line mismatch to form a self-excited shock, which may cause a big accident.