All information on LED display boards starting from LED manufacturing , product installation,cost to ROI
Wednesday, February 9, 2011
LED Display’s Working Principle
led display screen is a High-tech products that optical and computer technology in one.
LED product’s performance characteristics
led video display should have: animation features. Required LED display’s dots corresponding to the same area showing of computer’s monitor, we can it dot to dot with controlling PC. The function of text led display. Required text display stable, clear crosstalk; grayscale function. it Requires a detailed specification in the levels specified in gray. TV led video display except with animation, text display, grayscale functions, should be able to show the TV, s-videos,dvd players. rental led display aslo need the function to show the Live show,with hanging installation for different applications,and flight case for easy transportation.
The minimum and maximum viewing distances of a LED Display screen are measured depending on two fundamental characteristics of the screen – Pixel Pitch and Screen’s dimension:
Minimum viewing distance based on Pixel Pitch:
•the minimum distance is calculated converting into meters the pixel pitch. For example, a LED maxi screen with 10mm pitch has a minimum viewing distance of 10 meters, while a 20mm pitch screen has a minimum viewing distance of 20 meters.
Maximum viewing distance based on screen’s dimension:
•the maximum distance instead, depends on the screen’s dimension and it can be calculated multiplying x10 and converting into meters the number of maxi-screen’s square meters. For example a 4×3 meters (=12sq) can be viewed from 120 meters distance.
Viewing distance is one of the most important factors needed to determine the correct size of most indoor led screen and outdoor led screen.
For TEXT displays:
As a general rule: 1 inch of text is viewable up to 50 feet away or 25mm of text is viewable up to 15m away. The following diagram illustrates at what distance and character size that a stationary audience will recognize and understand the content of an electronic sign.
Viewing distance chart for led electronic signs
What is Pitch and Resolution:
The pitch of a LED display defines the distance between the pixels, expressed in millimeters. This fundamental measure determines the characteristics and the performances of a LED maxi screens: the pitch indeed is a defining factor of a screen’s viewing distance:
•The smaller is the pitch, the shorter is the minimum viewing distance, the higher is the total number of pixels present on the LED screen (and therefore higher is the screen’s cost per area).
•The bigger is the pitch, the longer is the minimum viewing distance, the lower is the total number of pixels present on the screen (and therefore lower is the screen’s cost per area)
The pixel pitch therefore determines the LEDs density, which is usually called Resolution. It is important to notice that while reducing the pixel pitch, the LED density increase exponentially: for example, reducing the pitch by the 50% on the number of pixels grow of 4 times.
India a country of billions - billions of people , billions of opportunities and billions of advertisements ...............reaching masses will always be a challenge.A report by consultancy firm KPMG stated that the US$ 5.2 billion advertising industry is set to grow at a compounded annual growth rate (CAGR) of 14 per cent in 2010, in comparison to the last year.But the question is where LED display boards as medium to reach masses will fit in.
LED display can be effective tool if it can fit in the existing boundary with a lot of innovation so basically it implies giving a greater value without diminishing any existing value. For eg state governments want to sell advertisements rights now and then(2-3 years) and its really a challenge for a company to organize advertisers and convey messages immediately , here LED display boards can add real value , as government while giving advertisement rights get into a obligation to advertise with legal authorize company to advertise for them and this can be good business for company as let say one PSU will like to spend 2 crs on public awareness by advertising through billboards and other means now when compared with lED display they not only have flexibility to advertise but also benefit of choosing different location given to a vendor through advertisement right.Same goes for other corporates.
Now only thing is to decide what government will be spending on public awareness , their are many firms like BEE , NDMA , SSA etc who want to reach masses , the trick is to find a collaboration from both end
AC responses of LED drivers are critical but usually ignored in LED display applications. AC responses affect the major performance of LED display panels, such as grayscales, linearity, EMI, and reliability. Although there is trade-off within these requirements, LED drivers can provide balance. This article will further explain the importance of the AC responses of LED drivers and PCB design techniques to help engineers to design LED panels with good grayscale images.
Minimum OE pulse width vs. Linearity
LED panel manufacturers are asking more on the grayscale improvement to enrich color of image on LED panels which satisfy audiences more. More than 1024 grayscales of each color is now a common requirement for full color LED panels. At the same clock frequency, short OE pulse width and response time (tr / tf) may help achieve more grayscales. Yet, the design of short OE pulse width sacrifices the linearity, which means the proportion between the input data and output brightness. For example, the output voltage waveform of in Fig.1 is shorter than the OE pulse width, and the linearity result is shown in Fig.2. Obviously, the linearity of LED luminance is no longer proportional to the setting of OE pulse width especially when OE pulse width is less than 0.1us. As a result, the linearity is not good for this condition.
There are different definitions of minimum OE pulse width on the market. Some vendors define it as the shortest OE pulse width that output voltage of can respond to, but this definition is only meaningful under good linearity condition.
Overshoot Elimination
The voltage overshoot on the output channels usually damages the LED driver, when an LED driver is turned off. This also influences the reliability of LED panels. The voltage overshoot results from the parasitic inductance between VLED and OUTn (output ports). Fig. 3 and Fig. 4 explain the experiment results of the voltage overshoot. In the experiment, inductors are added to the circuit to simulate the parasitic inductors of the PCB traces. The waveform on node CH1~CH3 in Fig.3 are shown in Fig. 4 respectively. The voltage on the output node (CH3) will reach 26.6V, which is much higher than the breakdown voltage (17V) of an LED driver.
The overshoot voltage can be calculated by the formula below:
V = L x di / dt
where V is the induced surge voltage;
L is the parasitic inductance;
di / dt is the current variation during switching.
There are three approaches to eliminate the voltage overshoot. First approach is to reduce the parasitic inductances. Because the VLED overshoot will also accumulate on the VOUT surge, the traces of power lines and every individual output channel should be as short as possible and the distributed capacitors between VLED and GND should be placed uniformly on the PCB to reduce the overshoot on VLED and VOUT.
The second approach is to switch the driving devices slowly. LED drivers with short response time (tr / tf) are not suggested since it will cause higher voltage surge. Choosing an LED driver with moderate response time (tr / tf) for different applications is sufficient.
The third method is to disperse the switching noise. LED panel manufacturers may choose LED drivers with staggered output delay of each channel to avoid all output channels to switch at the same time. By the staggered output delay between channels, the overshoot can be suppressed.
Conclusion
Carefully choosing LED drivers and designing with good PCB routing as instructed above help LED panel manufacturers improve the grayscales and reliability of LED panels. The latest LED drivers on the market, such as MBI5025 and MBI5039, provide balance to help LED panel manufacturers easily achieve better image quality on LED panels with good system reliability.
MIC Electronics Limited, an ISO 9001:2000 Indian Multinational Company, with a turnover of over Rs.325.00 Crores. We are the Only Manufacturer of True Color LED Video Displays in India and are proud to be rated among the top 10 in the World. MIC has many awards, accolades & recognition's to its kitty most of them for our ground breaking technological advances. Just to mention a few:
1. National Award from Department Of Science & Industrial Research Government of India -2000 for MIC’s Research and Development efforts.
2. LEEleDc tVroidneico IWndaulls htray s been put up in Indian Innovators Forum – Hall of Fame
3. Rated as the Best New Listing in 2007
4. Rated as the Best Under a Billion Company by Forbes – Year 2008
5. Over 25 TEC Approvals
With over 23 years of experience in LED Display products, MIC manufactures one of the best Full colors LED Video Displaysin the World. MIC’s LED displays have a very strong presence in the field of sports. Our LED displays have been used across the World in various events, a few of which are:
1. Perimeter Displays in Parammatta & Ecuador, South America
2. Displays Boards for Commonwealth Games – New Delhi
3. Various BCCI and IPL matches
4. National Games – Pune Stadium
5. Delhi Metro Rail Corporation.
6. Delhi Municipal Corporation – 50 LED Outdoor Billboards across Delhi
7. Indian Railways
MIC is capable of supply, erection and commissioning of the world class LED displays within stipulated timeframe due to its local presence backed by a strong and committed team of 500 professionals. We have wide range of products and completely integrated system which facilitates customization and content management as per customer needs backed by excellent service and support.MIC is a One-Stop solution provider for all LED Video Displays.
