Monday, April 25, 2011

【 Weak current College 】 ultra-high brightness LED in lighting applications in control technology 】

In the decorative lighting applications, available ultra-high brightness red, green and blue LED as light source, using the embedded microcontroller, the duty on certain only led glow brightness to achieve independent digital control to produce full-color variation effect.
1. structural arrangement of LED
Here to introduce the concept of a light emitting element, ultra-high brightness red, green and blue LED according to the color required proportion constitutes the glow element, each light-emitting unit at least arrange a red light LED, a green LED and a blue LED, then several of the same structure of light-emitting unit according to certain shape or pattern to arrange for a line or area light source. In the same light emitting element, LED should closely aligned, so you can make the LED's spot in the viewers eye image overlap. Adjacent light emitting unit Center distance should be the same, and the Center shall meet the following type:
Type: D shine to the adjacent cell's minimum Center; L for normal use when the view-point and the vertical distance from the light source position; θ as a minimum resolution of the human eye.
LED decorative lighting applications in the control circuit can be independent control of each light-emitting unit three led brightness levels, you can control each light unit-red, green, blue three colors in proportion to each light-emitting unit leveling out many different colors. If at the same time control different emitting unit displays a different color, you can make the entire decoration light emitting parts presents a colorful effect. If the light-emitting unit into certain patterns or text to a shape, you can control the lighting to produce dynamic patterns, text changes.
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2. the structure of the control circuit
The whole circuit is divided into embedded controller circuit and control circuit two parts displayed, display the control circuit is divided into three modules: module, green, red and blue module module. The structure of each module, the module with embedded MCU connection methods. Each module consists of several LED driver IC cascaded, of which the first level LED drive through cable and next level LED drive connections. Embedded microcontroller by the signal line and the LED drive in the module. Each LED driver IC has several outputs, each output can meet under color requires a or more only LED, the same module in the output are the same color as the LED. Red, green, blue three module internal LED drive structure, as well as modules and embedded MCU connection structure are identical.
3. control principle
Via built-in to the program of micro-controllers, LED by the micro-controller to send control signals driver chips and the data LED driver IC under control signal and data requirements to produce the appropriate action, which LED to a realization of a separate control. If the micro-controller continuously to the LED drive constantly send control signals and data, enabling continuous coordination LED under control, the overall lighting produces a variety of colors, a variety of dynamic change. The entire display control circuit in accordance with a control needs, divided into red, green, blue three control modules, each module of the structure and control principles are basically the same.
Micro-controller via a data cable to the LED drive serial data input pin to send serial data to another data output cable to the LED drive clock signal input pin sent clock control signal, the clock control signals, serial data LED driver IC internal shift register. When the received data, micro-controller to the LED drive data latch input pin issued latch signal so that the LED drive latch already stored data. Then the microcontroller to LED drive output allows control pin output enable signal is given, so that the LED drive depending on the storage of data-driven LED light. Because of the LED drive storage data determines the high and low level LED driver PIN combinations state the length of duration, that is, each lit LED or off the length of time, so as long as the adoption of the microcontroller changing output-LED drive serial data and clock control signals, data latch signal, output enable signal common tie, you can flexibly control LED lighting condition. For example, the control LED to the human eye could not blink rate rapid on-off and control LED in each light off cycle inner glow, the proportion of the time, we will be able to control the led brightness effect. Through emitting each LED brightness control, enables each LED produce 256-level brightness level. On three modules in the red, green and blue LED at the same time, maintain control of red, green, blue three color LED by any combination of different brightness levels, which have 256 × 256 × 256 (16777216) color effect. If the red, green, blue three color LED by a certain percentage and certain infrastructure arrangement, according to this kind of control, you can display a variety of colors, a variety of designs, text, and its combination of arbitrary dynamic display effect.

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