LED TV - The Truth About So-Called LED Televisions

 

There has been a lot of hype and confusion surrounding the introduction of "LED" Televisions. Even many marketing representatives and sales professionals that should know better are falsely explaining what an LED Television is to their prospective customers.
To set the record straight, it is important to note that the LED designation refers to the backlight system used in many newer LCD Televisions, not the chips that produce the image content.
LCD chips and pixels do not produce their own light. In order for an LCD television to produce a visible image on a TV screen the LCD's pixels have to be "backlit". For more specifics on the backlighting process needed for LCD Televisions, refer to my article: Demystifying CRT, Plasma, LCD, and DLP Television Technologies.
LED TVs are still LCD TVs. It is just that these new sets use LED backlights rather than the fluorescent-type backlights used in most other LCD TVs.
In other words, LED TVs should actually be labeled LCD/LED TVs.



How LED Technology is Used In LCD TVs
The are currently two main ways that LED backlighting is applied in LCD flat panel televisions.
One type of LED backlighting is referred to as Edge Lighting. In this method, a series LED backlights are placed along the outside edges of the screen. The light is then dispersed across the screen. The advantage of this method is that the LED/LCD TV can be made very thin. On the other hand, the disadvantage of Edge lighting is that black levels are not as deep and the edge area of the screen has a tendency to be brighter than the center area of the screen.

Edge Lighting

The other type of LED backlighting is referred to as Full-Array (also referred to sometimes as Full LED). In this method, several rows of LEDs are placed behind the entire surface of the screen. The advantage is that these sets can employ "local dimming". Local dimming means that each LED or a specific group of LEDs can be turned on and off independently within certain areas of the screen, thus providing more control of the brightness and darkness for each those areas, depending on the source material being displayed. On the other hand, LCD TVs that employ full array or full LED backlighting are thicker than LCD TVs that employ an Edge-lit LED light source.

Full-Array (also referred to sometimes as Full LED)

If you are considering the purchase of an LED/LCD Television, find out which brands and models are currently using the Edge or Full Array method and take of a look at each type when you go shopping to see which type of LED backlighting looks best to you.


LED/LCD TVs vs Standard LCD TVs
Since LEDs are designed differently than standard fluorescent backlight systems, this means that the new LED backlit LCD sets offer the following differences with standard LCD sets:

1. Lower power consumption.
2. No Mercury used as in some other LCD backlight systems.
3. More balanced color saturation.
4. In LED/LCD TVs using the Full Array blacklight method, there is little or no light leakage in dark scenes. This contributes to even better black levels than traditional or LED Edge-lit LCD televisions.
5. LED/LCD TVs that use the Edge backlight method can be made much thinner than both standard LCD and Full Array LED/LCD televisions.

The only true LED-only TVs (not to be confused with OLED, which is a different technology) are the ones you see in stadiums, arenas, other large events and "high-res" billboards. (See Example).
LED backlight does represent an advance in technology, mostly in bringing LCD TVs up to the performance levels of Plasma Televisions in terms of black level performance, and, at the same time, making even thinner LCD TV designs possible.
On the other hand, LCD TVs that utilize LED edge or full array backlighting are more expensive than non-LED backlit sets. However, as they become more common, prices will continue to come down.
I have been impressed with the image quality of the LCD/LED TVs I have seen so far (see example shown by Samsung at CES 2009) and feel that they do deserve purchase consideration. I have included a few LCD/LED TVs on my latest LCD Televisions 40-inches and Larger Top Picks List and will add more as time goes on.
For more information on LED technology used in LCD Televisions, check out a report from CDRinfo.

LED Use in DLP Projection Televisions and Video Projectors
LED lighting is also used in some DLP televisions and is also making its way into DLP video projectors. In both cases, an LED supplies the light source intead of a traditional projection lamp. In a DLP television or DLP video projetor, the image is actually produced in gray scale form on the surface of the DLP chip, in which each pixel is also a mirror. The light source (in this case an LED light source made up of red, green, and blue elements) reflects light off of the DLP chip's micromirrors and is projected onto the screen. Using an LED light source in DLP projection televisions and video projectors eliminates the use of a color wheel. This enables you to see the image on the screen without the DLP rainbow effect.

555 Based Simple Servo Controller

Servos are very useful devices for a number of projects, such as robotics, automation or just remotely controlling something, eg model car steering. They are relatively cheap and easy to get hold of, but controlling them is a little tricky as they requrie precise timing to command the output to move to a desired location.

Most servos have a 50Hz refresh rate (20ms) at which point a pulse of between 1 and 2ms is used to command the output to move between -45degrees and +45degrees.

A 555 timer can be used to command the output with a simple circuit and adjusted using a potentiometer.

Circuit diagram:

Click to Enlarge

The circuit is pretty self explanatory. We use a 555 timer IC to generate a pulse every 20ms with a duty cycle of between 5 and 10% (1-2ms). All the parts used are common components. You can drive multiple servos with the same signal using this circuit to all have the same output or build multiple driver circuits to command many servos to different outputs.

Servos operate with a voltage between 5 and 6V, do not exceed this or you will damage them. Whereas the 555 timer will operate up to 15V.

Also note that servos require alot of current when commanding them and also to hold a position under load, this can be up to a few amps! So make note of this when designing your power supply.

“The Beetle Robot”

The following article will show you how to build a simple robot, called “The Beetle Robot”,  It’s great for beginners and easy to do.
This is the Beetle Robot v. 3 you are going to build:

Before starting, I suggest you to read the complete tutorials. This will greatly lower the chances of you making a mistake.

Tools Needed:

• soldering iron Â
• electronic solder
• diagonal cutter
• Mini glue gun

Components for the robot

• 2x – small 1.5 Volts motors
• 2x – small paperclips
• 2x – big paperclips
• 2x – batteries AAA or AA
• 1x – battery holder AAA or AA
• 1x – 2 cm of heat shrink
• 1x – wooden pearl  (for the caster)
• 1x – meter of electric wire
• 2x – Sub-mini lever SPDT switches
  

Here are the serial numbers of the components and tools from RadioShack .

Component

Number

soldering iron	64-2184
electronic solder	64-006
diagonal cutter	64-2951
1.5 Volts motor	273-223
battery holder	270-398
SPDT switch	275-016

Most of the components can be bought for much cheaper at Digi-Key, Jameco, or similar.
At RobotShop you can find the dual AA battery holder and the small DC motor. You can find these components at any good electronic store.
Here is all the parts for the construction the beetle robot.

1. Cut the electric wire in pieces of 6 cm each, 13 times.

Strip 1 cm at each end.

2. Regroup all the components.


3. Solder each wire to each components except the two batteries.

4. Take the battery holder and make a connection to the connection.

This will give a third connection.See picture below.

The blue wire is the third connections

5. Turn the battery holder up side down so the batteries point to the ground. Glue the two switches on the battery holder in a V form.



6. Glue the motor beside each switch so that the shaft touches the ground



7. Take the big paperclip and make the caster like the picture below.

You can make a nice looking caster or a normal one


I prefer the nice one

8. How to make the connection



9. Take the small paper clip and bend them to make antenna.

Glue them to the switches and don’t put to much glue.

Add 1 cm of heat shrink to the shaft of each motor.


10. Add the batteries in the battery holder and put it on a flat surface to see your creation take life. Congratulation!

Capacitance
Capacitance is typified by a parallel plate arrangement and is defined in terms of charge storage

 

where

• Q = magnitude of charge stored on each plate.
• V = voltage applied to the plates.

 Capacitors

Capacitors are the second most commonly used component in electronics. They can be thought of as tiny rechargable batteries -- Capacitors can be charged and discharged. The amount of charge that a capacitor can hold is measured in Farads or the letter F. However, 1F is too large for capacitors, so microfarads(µF) and picofarads(pF) are used. micro = 1/1,000,000 and pico = 1/1,000,000,000,000

So 100,000pF = 0.1µF = 0.0000001F

We will only be discussing two types of the most commonly used capacitors: Ceramic and Electrolytic.

• Ceramic capacitors are brown and has a disc shape. These capacitors are non-polarized, meaning that you can connect them in any way. To find the value, you simply decode the 3 digit number on the surface of the capacitor. The coding is just like the resistor color codes except that they used numbers instead of colors. The first 2 digit are the significant figures and the third digit is the multiplier. These capacitors are measured in pF.
  
  
  
  
• Electrolytic Capacitors has a cylinder shape. These capacitors are polarized so you must connect the negative side in the right place. The value of the resistor as well as the negative side is clearly printed on the capacitor. These capacitors are measured in µF.
  
  

 Resistor

Resistors are one of the most commonly used components in electronics. As its name implies, resistors resist the flow of electrons. They are used to add resistance to a circuit.

The color bands around the resistors are color codes that tell you its resistance value. Recall that resistance is measured in ohms.

The tolerance bands indicates the accuracy of the values. A 5% tolerance (gold band) for example, indicates that the resistor will be within 5% of its value. For most applications, a resistor within 5% tolerance should be sufficient. To get the value of a resistor, hold the resistor so that the tolerance band is on the right. The first two color bands from the left are the significant figures - simply write down the numbers represented by the colors. The third band is the multiplier - it tells you how many zeros to put after the significant figures. Put them all together and you have the value. NOTE: There are resistors with more bands and other types for specific applications. However, 4 band resistors(the ones discussed here) are the most common and should work for most projects.

One last important note about resistors is their wattage rating. You should not use a 1/4 watt resistor in a circuit that has more than 1/4 watt of power flowing.

For example, it is NOT okay to use a 1/4 watt resistor in a 1/2 watt circuit. However, it is okay to use a 1/2 watt resistor in a 1/4 watt circuit.

 Ohm's Law

Ohm's law is one of the most important concepts in electronics. Fortunately it's only a very simple mathematical relationship between current, voltage, and resistance.

According to the Ohm's law, voltage equals current times resistance which is expressed in the following equation:

E=IR
where E = voltage, I = current, and R = resistance

For example, if
I = 0.1A
R = 10k
then
E = 0.1 * 10k

E = 1000 volts

Note: "k" stands for "thousands". So 10k = 10,000 ohm