This time the author explains the characteristics of LED curtains, a supplement for low-resolution screens the same technology when you do not have a large budget.

Adrian Morel

LED technology is a quinciañera which has a long history behind it. The author offers a journey in time to talk about its origins and its current characteristics.

By: Adrian Morel *

When choosing an LED display, a number of parameters that should be contemplated to avoid further disappointments. The author suggests some of them.

by Adrian Morel *

When deciding between the selection and acquisition of an indoor or outdoor LED display comes, or pixel pitch Virtual versus real, the answer seems easy, but there are some details to be taken into account. At first glance, many think that the difference between indoor and outdoor screens is just more or less light output, partly if it is, but there are other issues as well. Others think that a virtual resolution is equivalent to a real or similar and that deserves its clarifications.

Only virtual industry classifies

Importantly, suddenly and without warning, the LED display industry has decided to rename or reclassify their products without telling your client. That is, a couple of years ago, the industry managed only terms of actual pixel pitch in millimeters. Today, it seems that people marketing or communication has advised entrepreneurs LED screens that refer to them only in virtual terms, which is not the same as actual pixel pitch.

This lack of pre-notice or unclear communication is not a happy situation, because when we are reading on the Internet that a screen has 7 mm resolution, to tell the truth, it would be clear that the same screen is 7 mm virtual and 14 mm Real (which is not the same as actual 7 mm). Although the difference may seem subtle, this confuses the buyer because it is offering one thing for another.

Therefore, the best way to know whether we are choosing a virtual or real screen, is counting the physical LEDs per square meter. Such information is basic and is in any brochure.

Advantages and disadvantages of virtual vs. real

The emergence of virtual models has significantly improved the resolution of the screens. This technology basically can occur in two ways.

Image scanning 1.Doble
2.Incorporación of an additional LED.

Double Swath image

The double sweep reads twice instead of once and as you already know the video is a sequence of images in which the resolution is improved when more frames are reproduced per second. For example, in the case of film which normally has 35 mm 24 frames per second, it would be read electronically 48 frames per second. The PAL system passes to 25 50 frames per second, and finally the NTSC system to 30 60 frames per second.

This double scanning system is an incredible improvement to the human eye because 20 mm screen, which normally 20 meters and looks good, with a virtual resolution, looks as if it were a resolution 10 mm. That is, equidistant better resolution.

The question would then be a million dollars on what terms it looks better? For example, if we compare side-by-side screen 20 actual mm with a screen 10 virtual mm we can say that in terms of colors no big difference, since both are 4.4 trillion colors, in the case of screens first line or recognized brand. In terms of comparison contours, that if we can say that the difference is noticeable being the largest virtual definition. If we compare letters or tiny details, the difference is incredibly amazing. 10 screen virtual mm can play even the smallest detail.

Importantly, the virtual resolution is a significant step forward for the human eye, but the double sweep does not get along with video cameras, because they generate distortion and the famous Moiré effect, which blurs the image, contours and appear unwanted striations.

Incorporation of an additional LED

This additional LED or LEDs in the RGB fourth process also contributes to the virtual resolution, improved or extended (ENHANCE resolution). As you know, to make the color combination requires three basic colors are red, green and blue (RGB or English Red, Green, Blue). optical engineers have realized that there are colors that are repeated and if additional LED is added, increasing the illuminated surface, increases the resolution. This extra LED can be both red and blue. The difference is that when the LED room is red, the screen is of medium resolution and not recommended, because it saves just where it should not ahorar, it would be like buying the cheapest parachute or buy a parachute just because I like the color same. Many companies choose to put the red LED because it is the cheapest LED industry and thus reduce cost, but sacrificing quality. Other companies, however, added as a fourth LED green. This color significantly increases the resolution, and whether it is an expensive LED, many chip companies emphasize real or substantial improvements, regardless reduce costs.


To assess the quality and performance of a factual LED display must take into account minimal details that make the core business and good resolution. The colors of the optimal resolution screens are measured in trillions of colors. Virtual technology substantially improves the resolution of details and letters in the video and finally is good to ask if the screen is used only live where the Double Swath technology is ideal or if the screen used to be broadcast on television, where fourth virtual LED technology is preferred for its low or almost zero Moiré effect.

* Adrian Morel is CEO of Lighthouse Technologies and can be placed in your office Califonia (

Recall that in last year, Garth Powell delved around topics filtering and isolation of AC power. On this occasion will talk about voltage regulation.

by Garth Powell *

So far I have written about the unique likeness of each professional electronic installation, is the live sound, broadcast on radio and television, sports venues, nightclubs or automated audiovisual systems for boardrooms: all depend on the power supply by AC (AC). In the previous two articles we discussed the peaks and transients AC, the danger of multiphase power supply with noise problems and intermittent AC neutral, ground loops and compression power.

Some of these issues are crucial for each installation, while others only become important when the application ensures interest in maintaining the highest quality standards. For example, if we are supplying power to a computer system for an office or a full power amplifiers and high quality mixing consoles scenario, we must protect the equipment and make sure not to lose our programming. There is a fundamental need to protect and filter dangerous power fluctuations and noise that affect the basic operation of our equipment.

Other control technologies AC power are more specific depending on the application. There is no doubt that a boardroom will have no problem minimize compression power in its power amplifiers, since the quality of the audio to a slide show or seminar transmitted over the Internet does not require the highest resolution (unless is the boardroom of a record label).

However, in this respect there is another common concern to all applications in Latin America: the AC voltage regulation. In short, a voltage regulator adjusts the AC input voltage and corrects abnormally high or low voltages, feeding vital components with a constant stream of 120 VAC. While the voltage may be of some continuously in some areas of their city, state or country, it is important to understand that most of the equipment you specify were created for a constant supply of 120 VAC. Still, the average voltage in Mexico, to cite one example, is 127 volts. Although located within 10% of the optimum voltage components, this will raise the temperature of the power supplies of many commercial electronics.

Some vital components may experience significantly greater distortions (unless all circuit parameters programmed from the factory to be recalibrated 127 VRMS). And 127 volts is just the average What happens in 130 or 136 volts? the operation is affected. Some teams will be blocked or intermittently overheat due to abnormal increases in line voltage AC. In addition, abnormal low of less than 112 VAC voltage raise similar concerns. It may present the same phenomenon and intermittent greater distortions. For example, some video projectors can not receive a consistent supply under these conditions reduced voltage.

Of course, for many people in Latin America, this is not a startling revelation. Many electrical contractors and designers have spent years audiovisual systems using AC voltage regulators. But many of these units are bulky devices to maintain basic appliances and incandescent lights, installed behind a standby generator. Electronic devices today require much cleaner technology and stable regulation. Overvoltage regulator grandfather, with burnt and rusty rusty electrical contactors and high impedance circuits, creates the same amount of problems trying to solve in the current sensitive electronic circuits.

Many regulators brownouts can cause shock, create noise AC, significantly increase the impedance of the AC (severely limiting amplifier performance), or simply fail to handle the demands of running your AV system uncut form wave of the AC and adding distortions that adversely affect the image and sound quality. This is equally problematic for current microprocessing technologies, as these require a stable and clean source of AC power to prevent blockages, digital errors and loss of information.

It should be understood that various technologies have been developed for different applications. Control technology more practical voltage for lighting your home is not necessarily required for your video server, and the system would be ideal for machines large engines is not what would best for a rack of power amplifiers. Of the many technologies voltage regulator that are in the market, the most common are:

  • ferroresonant: it is a complex circuit capacitance and inductance transformer modulated to create a substantially constant voltage and reduce noise asymmetric. The circuit is moderately expensive and can work well in some industrial or laboratory environments. Unfortunately creates heat, no tolerance for dynamic loads such as power amplifiers, emits a very audible hum and projects a magnetic field of several meters. For these reasons, it is not a control technology ideal for audiovisual professionals microprocessing circuits or computer systems.


  • Amplifier / oscillator complete regeneration: essentially this is equivalent to a power amplifier with large oscillator operating 60 Hz input. Take the AC input voltage, direct current makes it synthesizes and then again a source of AC with low distortion. The advantage is exceptionally strong regulation (generally ± 0,1 VAC). It also reduces the distortion of the AC line and eliminates some of the symmetrical AC noise. Unfortunately, this technology is inefficient and costly end. A simple output capacity 10 amps can be worth several thousand dollars, reheat a whole enclosure and create serious distortions compressions current or AC signal when the capacity is exceeded. It is ideal for AC synchronous motors, not for professional audiovisual equipment.


  • active correction lift / reduction: This design compares the AC voltage with a reference amplitude and controlled distortion, and adds or subtracts a correction to the AC input (with a maximum correction of ± 20%). The regulation can be very good (usually ± 0,5 VAC). It is much more efficient than complete regeneration to 100%, but may suffer from a serious limitation of current and AC create noise and distortion itself, partly due to the exchange of circuits that are commonly used. This technology might work well for some low current audiovisual equipment, but can be overcome by a autoformer several leads with solid state switching for its power amplifiers.


  • Motorized Variac: This design uses a autoformer lift / reduction with various derivations. On the surface above a cut autoformer are exposed coils which contacts a brush, creating the appropriate AC voltage, either raising or lowering the voltage. A microprocessor constantly monitors the input voltage relative to the output voltage, and moves the wiper motor accordingly. This technology has good regulation (± 1 generally VAC), but has the disadvantage that the engine emits a very audible noise when placed in an area of ​​audio. This technology was created for laboratories performing constant voltage readings.

Since the coils are covered with fat, and make contact with a brush, high current demands create sparks and noise in the AC line. The brush must be replaced and coils cleaned every one to two years. This makes the technology impractical for long-term use in most applications. In addition, the contactor creates a relatively high AC impedance, which seriously affects the power amplifiers. While industrial versions mass of this technology have been used for decades by some traveling professionals A / V (particularly when following a diesel generator and erratic voltage output) systems, low noise and ultra-high resolution today require much more of its energy source.

Finally, but by no means to forget, is my favorite technology AC voltage regulation for A / V professional, broadcast on radio and television, recording and boardrooms alike.

Autoformer switching zero crossing solid state with various derivations: this circuit works very similarly to motorized variac, except that as the microprocessor input and output (comparator) indicates the regulator circuit to raise or lower voltage. This is achieved by solid state switches with zero crossing. Since multiple switches are used, there is no exposed coils, and electrical contacts remain tight and secure for many years to come. The regulation can be quite good (± 3 VAC) with a reasonably wide capture rate (90 135 VAC-VAC). This circuit also has a control features exceptionally good transient compression with very little current. Unfortunately, the solid state switching can create some noise from AC if not precisely calibrated so that a good design without this noise can easily cost more than $ 700. However, if you have the budget, this is an excellent candidate for sensitive components today, even if they are subject to the most demanding environments.

Keep in mind that the facilities that rely on backup generators (gas or diesel) should be followed by a voltage stabilizer if you have a system that requires a corresponding voltage even the 120 volts. This is because the output voltage specifications generators are based on a constant current charge at Any system A / V who has ever installed Seems? Of course not. The result is that the current demand rises suddenly, the generator produces very little voltage as low current demand, the generator produces too much voltage.

An AC voltage regulator is needed to control this. In addition, when a suitable AC regulator is combined with other energy control technologies, such as removing non-sacrificial surge and linear AC noise filtering, your system will be stable and secure, and your client will be well served.

*Garth Powell is a senior product designer and engineer sales chief Furman, a world leader in providing solutions for electrical control. It can be contacted at:


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