- Home >> Solution >> Appliances >> convenient tools
LED Controller Solution
With the development of the Internet and technology, and the continuous progress of society, there are more and more tools for people's entertainment and leisure. The LED controller can be made into a high-tech electronic toy that uses the "persistence of vision effect". Products such as the shaker stick made by it are one of the hot commodities. Its controller is a sensory effect based on the principle of human visual persistence. When shaking the LED controller, the persistence of human vision will generate a visual plane in the shaking area of the LED. When it is realized, the controller can make the above LED lights display text and graphics at the appropriate position across the air, so as to achieve the vision in this visual plane. The role of conveying information on the plane. This kind of finished controller is more and more common in various cultural and sports activities, increasing the effect of the event.
1. Design principle of LED controller
There is a phenomenon of persistence of vision in the human eye. It is because of the slow response of the eye that it enriches the human visual experience. This system is designed based on this principle and is a high-tech product of linear array LED motion imaging developed by the latest patented electronic technology. . When the LED controller is shaking in different positions, the LEDs on a straight line will display different columns of two-dimensional images, and use the visual persistence effect of the human eye to realize graphic scanning display. The control of the output signal frequency is realized by FPGA, and 32 light-emitting diodes are used to refresh on and off at different frequencies. When shaking, due to the persistent effect of human vision, a visual plane will be generated in the shaking area of the light-emitting diodes. The diodes in the visual plane will generate images in the shaking area through refreshing at different frequencies, so as to achieve the vision in the visual plane. function of conveying information. From data analysis, that is, the time required to move from one side to the other is 0.1s. If 0.1s is divided into 64 parts, the graphic display time of each column is 1562um. Each column corresponds to 32 LED light-emitting diodes, and then a corresponding column of the graphic is displayed in each part of the time, and a complete graphic display can be obtained.
LED is the abbreviation of light emitting diode (Light Emitting Diode, LED), also known as light emitting diode. This kind of semiconductor component is generally used as indicator light and display board. It can not only directly convert electric energy into light energy with high efficiency, but also has Up to tens of thousands of hours of service life, and can save electricity and other advantages. This design adopts the common cathode connection mode, when the voltage of 5V is applied to the anode of the LED, the LED will have a current flow, and the LED will emit light. When the two ends of the LED are at high level, although there is a small voltage difference, the current generated by the small voltage difference cannot drive the LED light to emit light. Generally, the driving voltage of LED lights is above 1.5V, and the current is above 200mA. The driving voltage and current of different LEDs are different. In addition, for the mercury switch module, as a mode sensor, because of the gravity, the mercury droplets will flow to the lower part of the container. If the two electrodes are touched at the same time, the switch will close the circuit, turn on the switch, and control the system. Image display.
2. Analysis of LED controller system scheme
The realization of the LED control module is made using the persistence of vision of the human eye. The LED light-emitting tube is used as the display of each column of the screen, and the left and right shaking plays the role of scanning. complete picture. However, in the LED display module, if the number of LED lights is too small, the resolution will eventually decrease when displaying text, so that the displayed image is not delicate enough, so this design uses 32 LED light-emitting diodes as the Example to illustrate.
In addition, during the shaking process of the controller, if the displayed text, images and other information are left and right asymmetrical, if the image information continues to be displayed during the retrace process, reverse ghosting will occur, resulting in the display of images or information. Error, this design uses mercury switch or inertial switch to solve this problem. When the controller is shaking, through the gravity of the mercury switch itself, the circuit will be connected only when shaking in a certain direction, and information such as graphics and text will be displayed at the same time, and the switch will be automatically closed during the reverse retrace process, and the LED will light up The diode does not display the content, so it can be controlled by connecting a mercury switch, so that the content can be clearly displayed when the LED controller is shaken from one direction to the other, eliminating the problem of ghosting.
3. LED controller development method
3.1 Hardware Design
The power supply VCC of the hardware circuit of this system comes from the FPGA. The 32 I/O interfaces in the system are connected to high-brightness LEDs and pull-up resistors in a common cathode manner. The I/O port outputs a high level to light up the small lamp. As an orientation sensor, it transmits a display status signal to the FPGA controller. The system hardware circuit includes 3 parts: Mercury switch module, LED display module and I/O interface module. Hardware circuit modules.
Among them, the mercury switch module realizes the function of the direction sensor to judge the shaking direction of the whole controller. The direction of the mercury switch is upward and slightly to the right. When the shaking stick shakes to the right, the sensor returns a rising edge signal through the I/O interface to realize the connection with the FPGA. information connection. When the FPGA receives the rising edge signal from the sensor, it starts to execute a cycle of display coding and transmits it to the LED display module through the I/O interface. This design FPGA experimental development board is based on EP3C5E144 of ALTERA Company as the platform.
During the display time of a cycle, the FPGA automatically shields the sensor return value during this period, and when the display cycle ends and the judgment takes effect, the FPGA receives the return value of the sensor module again. In this way, it is possible to avoid confusion in the displayed content when the shaking stick is shaken back and forth, such as the ghosting of the positive and negative fonts, which prevents the correct content from being displayed clearly and accurately.
3.2 Software Design
This design uses a combination of FPGA-based VHDL language and schematic diagrams to realize the design in a bottom-up engineering order. First of all, the bottom part is composed of 7 modules, which are: phase-locked loop, frequency divider, sensor signal primary determiner, sensor signal secondary determiner, feedback device, timing controller and output data selection and decoder.
(1) Frequency divider and timing controller module design: The frequency division module divides the input signal by 100 through the CLK clock signal input. The input signal is the output signal of the phase-locked loop, and the output signal FREOUT is used as the input of the timing controller. The timing The controller receives the 1MHZ frequency signal output by the frequency divider, receives the enable signal of the timing controller output by the central controller, outputs the timing execution end signal to the central controller, and outputs the font code data selection signal to the output data selection and decoding Device, this module is generated using VHDL language programming.
(2) Sensor signal determiner module design: The sensor signal determiner has two levels, the first level determiner realizes the preliminary judgment on the return value of the mercury switch, and makes necessary preparations for the second level determiner to judge the rising edge, which also integrates There are 3 intelligent judgment units', including two high-level timing intelligent judgments and one low-level timing intelligent judgment. The high-level intelligent judgment generates timing trigger signals of 2 seconds and 4 seconds respectively, and the low-level intelligent judgment realizes the generation of the timing reset signal of 2 seconds. The sensor signal secondary determiner strictly determines the rising edge of the primary signal. If it is a rising edge, the central controller with integrated feedback is enabled and allowed, and receives the feedback clear signal as one of the judgment conditions.
(3) Central controller module design with integrated feedback: This module receives the end signal of the timing controller and the enable signal of the central controller output by the second determiner, and outputs the enable signal of the timing controller and the feedback clearing signal to Second determiner. The controller receives the periodic display end signal from the timing controller, and outputs a display clear signal after processing, so that the display in one direction of the LED controller is valid while the display in the other direction is invalid when the LED controller is moving.
(4) Software top-level design: Seven modules are successfully written by seven independent VHDL programs and generate schematic components. Secondly, the top part is designed based on the schematic diagram, and the bottom VHDL components are added to the input and output ports according to the corresponding principles and then connected to form a complete circuit. There are two inputs and 32 outputs, which are: FPGA 20MHZ input, mercury switch return Value input, anode output of 32 LEDs.
4.The design concept of intelligent LED desk lamp
There are many kinds of lamps and lanterns on the market now, and common desk lamp all adopts 220V AC power supply to supply power, and fluorescent tube, incandescent bulb are light sources, and manual switch or touch-sensitive switch controls.
Now the desk lamp is almost a daily necessities of ordinary families, and there are manual and automatic desk lamps. People in modern society consume energy because they often forget to turn off the lights. As a necessity, it must have a beneficial impact on people's lives. It can make you not worry about not being able to turn on the light in the dark, and it can correct people's sitting posture. The single-chip microcomputer is controlled by the infrared sensor sensing the intensity of the infrared light of the human hand, and the single-chip microcomputer controls the LED drive circuit to control the brightness of the LED light, and the infrared sensor sensing system cooperates with the timing system to calculate the learning time of reading, exceeding the time on the timer single-chip microcomputer An alarm will be issued and the brightness of the LED light will be reduced to remind learners of the learning time and eye protection. When the power fails, the 5V rechargeable lithium battery can be used to power the LED light.
(1) Functional principle: In the design of table lamps, lighting requirements must be met, and different lighting methods and lamps should be selected according to different spaces, different places, and different tools, and the illumination and brightness should be maintained. For example: the lighting design of reading and writing desks should adopt vertical lighting, so that the brightness can be evenly distributed and avoid glare; in order to attract the attention of a large number of customers, the windows and merchandise displays of many shopping malls generally use strong light for focused and prominent lighting , its brightness is about 3 to 5 times higher than that of ordinary lighting. In order to make the three-dimensional sense, texture and advertising effect of the product better, many merchants often use directional lighting fixtures and color light to make the product more vivid. Has artistic appeal.
(2) The principle of economy: When designing lighting, you can't just think that more is better, the key is to be scientific and practical, and use it reasonably. Lighting design is mainly to satisfy people's visual enjoyment and aesthetics, and to maximize the beauty of the interior space, which is the unity of utility and aesthetic effects. Some lighting decorations in the society not only fail to enhance the beauty, but are self-defeating, causing power consumption, causing economic losses, and most likely causing light environmental pollution and harming the body. According to the lighting standards of modern society, because of the different uses and resolutions, the scales used are also different.
(3) Safety principle: Lighting design should not be used arbitrarily, and safety performance must be paid attention to. Because the lamps use power supply, the harm of electricity to the human body can be imagined, so it is necessary to take relevant safety measures such as electric shock prevention and circuit breakage prevention, so as to prevent accidents as much as possible and minimize the accident rate.
5. Component Design of LED Desk Lamp Solution
(1) Drive circuit: LED driver: In order to meet the requirements of different input voltage, output current and different LED numbers, semiconductor device companies have developed various white LED drivers. In addition to driving white LEDs, the driver can also drive blue LEDs or LEDs of other colors. In addition, the driver has the characteristics of constant output or programmable constant current output, so the driver can be used as a regulated power supply or a programmable constant current source.
(2) Requirements for LED drivers: LEDs are not only used for LCD backlighting, but also gradually used as lighting, flash and strobe equipment in recent years. White LEDs have also developed from small power to medium power and high power (current up to lO00mA). The flashlight of the light uses high-power white light LED to produce dazzling light in the night sky, and the advertising effect is obvious. The driver can be regarded as a special power supply that supplies power to the LED. It can drive white light LEDs with a forward voltage drop of 3.0-4.3V, and can drive multiple white light LEDs in series, parallel or series/parallel as required to meet the requirements of driving current.
(3) Commonly used LED power drive schemes: There are many schemes for LED power drive, and there are different schemes in the technical realization of LED power converters. According to the level of power supply voltage, LED power drivers can be divided into four categories: low-voltage drive (supply voltage 0.8-1.65V), transition voltage drive (supply voltage 4V), high-voltage drive (supply voltage greater than 5V) and mains power supply.
6. Debugging and solution of intelligent LED table lamp circuit
6.1 Problems with LED lighting angle of table lamps
Many LED lens packages are not the same, even if the light emitting angle (nominal angle) is uniform, the effect is also different, which makes the selection of the condenser even more difficult, and it is still not universal.
This design is definitely not uniform if there is no direct light that has been processed, and the spacing between the LEDs also has an effect. The light in the light-emitting angle of the LED is not uniform, but gradually weakens around the middle. This is why LED lamp products will use LENS or reflectors for light treatment.
6.2 Lamp LED efficiency is low (luminous rate)
The luminous efficiency of LEDs in this design is actually divided into two major parts: internal quantum force and external quantum effect. Generally speaking, the internal quantum effect is the effect of photons generated by electronic transitions. Decrease non-radiative transitions—reduce non-radiative recombination centers (mainly crystal defects) to form the same necessary energy level difference—
(1) effective doping;
(2) Lower the junction temperature.
6.3 Lamp LED brightness is insufficient
In this design, different grades of chips are packaged to produce different brightness, and the LED can be made brighter by increasing the current. When the circuit is low, the brightness is relatively dim.
6.4 Dead lights appear
The phenomenon of LED dead light in this design mainly has the following two situations: open circuit dead light and short circuit dead light.
The reasons for the open dead light are:
(1) The solder joints in the LED are unreliable; the solder joints of the chip are polluted; the electrical transition layer of the bracket does not meet the standard, and the wire is too thin, which leads to insufficient tensile force of the solder joints; the internal stress generated by not completely fixed leads to the loosening of the solder joints, etc. ;
(2) Caused by virtual welding during the welding process of LED and PCB.
The reasons for short circuit dead lights are:
(1) The anti-static (ESD) of the LED chip is poor, and the withstand voltage of the direct mode is less than 300v;
(2) Due to insufficient reliability or mismatch of the power supply, LED overcurrent and overvoltage are caused.
During debugging, the open-circuit dead light caused by the unstable solder joints in the LED is the cause of the material and process in the LED production process, and it is the quality problem of the LED. I passed the temperature test, thermal shock test, High temperature and high humidity aging test to screen out reliable solder joints. In this design, the dead light caused by the virtual welding process of LED and PCB welding is caused by the process of using LED processing products, so the problem should be solved from the following aspects:
(1) The welding temperature is kept at about 260 degrees Celsius, and the time is controlled within 3S to 5S;
(2) Before the soldering temperature returns to normal, it is necessary to prevent any vibration or other external force of the LED;
(3) The welding point is more than 2.5mm away from the bottom of the colloid;
(4) When the LED is bent or folded, it should pay attention to keep a distance of more than 2mm from the colloid to prevent the inner and outer brackets of the LED colloid from being separated from the gold wire.
In the design process, the reliability of the power supply is not enough or does not match, which will cause LED overcurrent and overvoltage to cause damage to the LED. Therefore, when selecting, we must pay attention to the reliability of the LED power supply and match it with the LED:
(1) In terms of voltage matching, LEDs are driven by a low voltage of about 2-3 volts, and complex conversion circuits must be designed, and LED lights for different purposes must be equipped with different power adapters. So this design is very careful in application;
(2) In terms of current matching, the normal working current of the LED is between 15mA and 18mA. When the supply current is less than 15mA, the luminous intensity of the LED is not enough, and when it is greater than 20mA, the luminous intensity will be weakened, and the heat will increase greatly, and the aging will be accelerated. The life is shortened, and it will be damaged quickly when it exceeds 40mA after testing.
Summarize
This paper uses high-brightness LED light-emitting diodes and mercury switches to design an FPGA-based LED controller model. This controller can not only illuminate and flash patterns, but can also be used as a commercial product. By time-sharing refreshing the high and low levels of the output ports connected to 32 light-emitting diodes to realize the display of text, patterns and other information, which greatly shortens the development cycle, improves the stability of the system, and improves the system upgrade and expansion conditions.
The above are the details of the LED controller solution introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have the electronic function development needs of LED lights, you can trust us. We have rich experience in customizing and developing electronic products. We can evaluate the development cycle and IC price as soon as possible, and can also calculate the PCBA quotation. We are a number of chip agents at home and abroad: Songhan, Yingguang, Jieli, Ankai, Quanzhi, realtek, with MCU, voice IC, Bluetooth IC and module, wifi module. Our development capabilities cover PCB design, single-chip microcomputer development, Bluetooth technology development, software customization development, APP customization development, WeChat official account development and other hardware and software design. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS earphones, the development of Bluetooth earphone speakers, the development of children's toys, and the development of electronic education products.
- TOP