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LED display knowledge

LED display knowledge

LED

Light emitting Diode, LED.

LED Display Screen

LED screen it is one product through control its semiconductor diode’s display usage, to display different kinds of signal like text, graph, image, flash, market, video, kinescope signal etc.

LED screen can separate to graph-text screen and video screen, they are set up by led dot matrix. Graph-text screen can display Chinese text, English text and image synchronization; Video screen use pc control it. Display vivid graph-text and image synchronization. Also it can display two-dimension/three-dimensional flash, kinescope, TV,VCD ect.

Indoor or Outdoor screen

The name of indoor or outdoor screen come from its using environment, or they are near the same.

What are they different? First it is the brightness. The brightness of outdoor will be about several 10 times than indoor one. So of you mount a indoor screen outdoor, just like you put a TV in outside, the brightness will be not enough. In order to increase the visualable distance of outdoor screen, we must use high brightness LED. On one pixel we need put in one high brightness led. Secondly, Outdoor screen would have more environmental fitting ability. Like waterproof, proof the sunshine shoot it directly, dust-proof, defend the high temperature, windproof, thunder-proof etc. But indoor screen not need consider those problem.

Static led screen

Static screen is comparative with scanned screen. When static screen display text, image, video, the diode of screen bright at the same time. But the scanned screen use the characteristic of eyes’ vision stayed temporary, in a very short time it can bright every line’s led. Everyone know, LED is using time’s interval to work. So the cycle of brightness and bright the diode is very important. With the diode, static screen will be more brightness than scanned screen. Static screen usually use in outdoor, and scanned screen usually use in indoor to save the driver.

As the develop of led material technique, led diode’s brightness higher and higher. Now scanned screen also was used in outdoor to save the cost. Of course it will have higher demand to the driver and controlled department. The demand to the driver’s chip-set also higher.

Real pixel screen

Comparative with the virtual pixel screen. Simply, red/green/blue only take part in one time’s imaging to got more brightness

Virtual pixel screen


Virtual pixel screen use software to control the diode take part in border diode imaging, in order to got more distinguish rate using less diode. It can increase 4 times of the distinguish rate

Every people know it, the most cost of led screen is the diode. How to make the diode cost less is the technique pursuing. And the virtual technique it is a developed direction. Virtual technique it is a not just a diode simple take part in imaging. To the brightness and the grey scale influenced also very big. So controlled system and the driver system’s assorted are demanded, combine with the software arithmetic and driver chipset’s response time to save the diode cost under the same brightness.

SMT

Weld the diode to the circuit board directly we call it SMT. It have the nicer heat-out ability and color equality. Because it weld the diode in circuit board, it is easer for maintenance, larger reduce the maintenance cost.

SUB-SMT

SUB-SMT encapsulate the diode to rectangle, then connect the RGB three dots to one pixel building up to module, we call it diode inserted real pixel.

For the display effective of those two kinds screen, the effect of SMT it is more near to plane TV. The other one’s color will be not so good. But price will be cheaper a lot. Because in the past two years, there are only module full color and SMT full color, and the price of SMT full color is so height that most people can’t afford it. And module full color’s effective is no good and hard to maintain. In this situation, SUB-SMT full color display screen come out.

Scaned driver circuit

The Function of scaned driver is produce scaned signal, to make every scan line turn on one by one. It depend on the simple register and amortized amplifier. Shift register static state and dynamic one. Static shift register put the electricity in the same location average. It is a steady situation. Dynamic shift register put the electricity in the pole’s node. Shift register are built up reverse organ and transfer door. Static shift register are built up with for reverse organ and 4 transfer door. Static shift register are built up with two reverse organ and 2 transfer door. Ordinary, if level scaned rate it is lower, we use static shift register; If data driver’s working rate higher, we usually use dynamic shift register.

Principle of Display Scaned

Different enterprise’s led screen have different configuration, but its display scan circuit near the same. Dual color LED screen’s display scaned circuit as showing of Photo1.In photo1,IC1、IC2 are the data flip-latch circuit 74HC59, They lock red and green data separated, function of them: 1. serial enter 8 bit then out put in parallel; 2. data lock and save, and clear out function; 3. Out put stronger driver capability; RPB1 and RPB2 are limited resistance, choosing their numerical value as the color and module’s brightness.

ML1 is a dual color LED display module, it have 64dots LED(8×8=64dots).Thereinto,8 legs are red signal inputting port, 8 legs are green signal inputting port, 8 legs are line controlled inputting port, total 24 legs

Dynatron Q0, Q2, ...Q7 are for ling choosing and driver function,IC3 is 3-8’s address coding circuit 74HC13, Eight choosing fan-out port separated control relevant line.

In photo’s circuit is led screen’s principle circuit, its data transfer mode is data transfer and line signal asynchronism transfer: First, at one time transfer 8 bits red and green data to circuit IC1 and IC2 and lock the data, then transfer zinc... The design of scaned circuit board’s cost will be lower, so most of the enterprise design the circuit as two side, then we can save 1/3 circuit cost. In display module’s correspond dimension range, we should set up all parts of an apparatus as in photos, corresponding it is have to workout its double deck press circuit board. So IC1’s circuit is most fit for dot matrix scaned led display driver. Display the scaned circuit is use serial transfer mode. Then we can save the position of the circuit wafer, and fit for the transmission between screen and computer.

IP defend scale

IP defend scale explanation(according to EN60529/IEC529 )

Defended grade IP54,IP it is a letter, Number 5 is first badge number. Number 4 is second badge number. First badge number means contact defend and exotic protect grade. Second badge number means waterproof protect grade.

contact defend and exotic protect grade waterproof protect grade
First number Defended range Second number Defended range
Name Explain Name Explain
0 No defend —— 0 No defend ——
1 Defend 50mm diameter or bigger solid object. detector, sphere diameter 50mmm can’t enter totally 1 dripping defend Virutal Dripping won’t injure it
2 Defend 12.5mm diameter or bigger solid object. detector, sphere diameter 12.5mm can’t enter totally 2 Cabinet 15 degree slant, dripping defend Cabinet 15 degree slant to every side, the dripping won’t injure it.
3 Defend 2.5mm diameter or bigger solid object. detector, sphere diameter 2.5mm can’t enter totally 3 Defend spilling water 60degree spilling water won’t injure it.
4 Defend 1mm diameter or bigger solid object. detector, sphere diameter 1mm can’t enter totally 4 Defend gushing water Gushing water from every side won’t injure it.
5 Dustproof It is impossible to block out all dust. But the dust coming won’t injure the equipment. 5 Defend shooting water. Shooting water from every side won’t injure it.
6 Block out the dust When cabinet’air pressureis 20millibar,it is not allow to come with dust. 6 Defend strong shooting water. Strong shooting water from every side won’t injure it.
Detector's diameter can't pass through the hole of the cabinet 7 Short time foundering defend In the standard press, when it is foundering, water can’t go into the cabinet.

 
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