led traffic display

LED traffic display 02985453602 satisfied Vincent photoelectric brightness control method to introduce you to two large LED screens. The first method: changing the current through the LED, the general LED tube allows continuous operating current of about 20 mA, in addition to the red LED has saturation, the other LED brightness is substantially proportional to the current flowing through; the second Methods: The method is to use the human visual inertia with a pulse width modulation method to achieve gray scale control, that is, periodic changes in light pulse width (duty ratio), as long as the repeated cycle of light short enough (ie, refresh frequency high enough), the human eye can not feel light-emitting pixels in the jitter. Since the pulse width modulation is more suitable for digital control, so in general the use of computer to provide LED display today, almost all the large LED screens are controlled using pulse width modulation gradation. LED large screen control system typically consists of three parts, the main control box, scanning plate and display and control device. Get a screen pixel control box from the computer's graphics card in each color luminance data, and then reassigned to the number of pieces of scanning plate, each scan board responsible for controlling the number of lines (columns) LED screen, and each row (column) the LED display and control signals are transmitted by serial fashion. There are two serial transmission display control signals: one is the scan board centralized control of each pixel grayscale scanning plate from the luminance values ??of pixels in each row of the control box of decomposition (i.e. pulse width modulation), Then the opening of each row LED signal pulse form (lit 1, off = 0) by using the serial transmission line to the corresponding LED on, control it is lit. This approach uses fewer components, but the large amount of data serial transfer, because in a repeating cycle of light, each pixel requires 16 pulses at 16 gradation, 256 gradation required in 256 pulse, because the device operating frequency limit, generally only the LED large screen to do 16 shades of gray. Another method is to transfer the contents of the Whiteboard serial switching signal not every LED but an 8-bit binary brightness value. Each LED has its own pulse width modulator to control the lighting time. Thus, in a repeating cycle of light, each pixel in the 16-level gray scale needs only four pulses, only eight pulses of 256 gray scale, greatly decreasing the serial transmission frequency. With this decentralized control LED large screen gradation method can easily achieve 256 gray scale control. Traffic LED display, preferred Shaanxi Hi-Tech Optoelectronic, welcome to buy!