miércoles, 10 de agosto de 2011

OPERATION OF A TELEVISION APPARATUS 




A television can be basically divided into two parts, namely: the first one dedicated to the reception and the second charge of producing the image and sound. The basic operation of a TV has not changed much in recent years but the components are used, many of them now being integrated circuits.

 
Production of the image. TV signal

 
Once we understand the operation of the cathode ray tube as an essential element for the imaging, we will see electronic devices which make possible the formation of moving images on the screen of television.

 
The most logical is to analyze how a television signal, ie, how they form and what features it has. The transmission of color television signal basically consists of four distinct stages: the first is obviously capturing a real image using a camera suitable for it.The video signal to transmit the image information and sound  In this process, the light from outside is broken down into three components: red, blue and green. Next is to convert light rays captured by the camera into electrical signals called "Video". After obtaining video signals are sent to the receiver by some form of modulation. Finally, we must send each signal to its corresponding barrel, that is, the signal from the red light component will be sent to red canyon, and so do the signals from the blue light component and the component green light from the image to be reproduced. Parallel to this process is the transmission of the signal light component corresponding to the black-white image, in order to be displayed also in black and white monitors who are not prepared for reproduction in color. Currently there are several systems used to perform the transmission of video signals, such as NTSC, PAL or SECAM .. However, all will be compatible with each other because, otherwise, would be quite uncomfortable, if not unfeasible, the marketing of television where they could only reproduce images captured by the system. The same happens with the TV in color should occur with black and white. There must be a full compatibility to view images captured in black and white on a color monitor and be able to view images captured by a system of color in a black and white monitor, although obviously in the latter case, the images will be seen in black and white. The idea, therefore, is that the information contained in the video signal must be identical in color and black and white as well as profitable in both types of receptor. The color signal, called "chroma signal or chromium," will be used only in the recipient of color, while white and black, called "video luminance signal" will be used both in color monitors and in white and black.The video signal is broken into three different signals: red, green and blue Each signal is sent to its corresponding barrel Once the signal has been achieved through a video camera to be sent to a TV receiver that can be reproduced. This is accomplished by modulating a signal with it much more often called radio frequency carrier. This modulation is a modulation in amplitude. This signal is received by the receiver circuit, which is built on the same TV. Application of the video signal to T.R.C. Once collected by the receiver signal is amplified by a "video amplifier." After amplification of the signal is passed to implement the TRC. Without any signal applied to the cathode of CRT, it would be about 160V or so. The grid itself is at a lower voltage, because the grid is negative with respect to the cathode.The black signal stops the flow of electrons towards the screen If the signal received by the TRC is for a black, it will be a high voltage, since the camera dark tones produce high voltages. When high voltage is applied to the TRC, this will increase the tension over the 160V. This increased tension will cause the grid is more negative with respect to the cathode and therefore fewer electrons pass through the tube. Passing fewer electrons will have fewer crashes on the screen and therefore the phosphor screen will not emit much light. This results in a dark spot on the screen. 
These signals inform the receiver that it has finished transmitting a full screen and therefore now proceed to issue a new screen, starting again for the top corner.
 


MATERIAL BAJADODE LAPAJINA:http://www.angelfire.com/al2/Comunicaciones/Sistemas/tv22.html

 

 
MATERIAL BAJADODELA PAJINA:http://aula2.elmundo.es/aula/laminas/lamina1099563554.pdf
OPERATION OF A TELEVISION APPARATUS
 
A television can be basically divided into two parts, namely: the first one dedicated to the reception and the second charge of producing the image and sound. The basic operation of a TV has not changed much in recent years but the components are used, many of them now being integrated circuits.
 
Production of the image. TV signal
 
Once we understand the operation of the cathode ray tube as an essential element for the imaging, we will see electronic devices which make possible the formation of moving images on the screen of television.
 
The most logical is to analyze how a television signal, ie, how they form and what features it has. The transmission of color television signal basically consists of four distinct stages: the first is obviously capturing a real image using a camera suitable for it.
 
 
The video signal to transmit the image information and sound
 
In this process, the light from outside is broken down into three components: red, blue and green. Next is to convert light rays captured by the camera into electrical signals called "Video". After obtaining video signals are sent to the receiver by some form of modulation. Finally, we must send each signal to its corresponding barrel, that is, the signal from the red light component will be sent to red canyon, and so do the signals from the blue light component and the component green light from the image to be reproduced. Parallel to this process is the transmission of the signal light component corresponding to the black-white image, in order to be displayed also in black and white monitors who are not prepared for reproduction in color. Currently there are several systems used to perform the transmission of video signals, such as NTSC, PAL or SECAM .. However, all will be compatible with each other because, otherwise, would be quite uncomfortable, if not unfeasible, the marketing of television where they could only reproduce images captured by the system. The same happens with the TV in color should occur with black and white. There must be a full compatibility to view images captured in black and white on a color monitor and be able to view images captured by a system of color in a black and white monitor, although obviously in the latter case, the images will be seen in black and white. The idea, therefore, is that the information contained in the video signal must be identical in color and black and white as well as profitable in both types of receptor. The color signal, called "chroma signal or chromium," will be used only in the recipient of color, while white and black, called "video luminance signal" will be used both in color monitors and in white and black.
 
 
The video signal is broken into three different signals: red, green and blue
 
 
Each signal is sent to its corresponding barrel
 
 
Once the signal has been achieved through a video camera to be sent to a TV receiver that can be reproduced. This is accomplished by modulating a signal with it much more often called radio frequency carrier. This modulation is a modulation in amplitude. This signal is received by the receiver circuit, which is built on the same TV.
 
Application of the video signal to T.R.C. 
 
Once collected by the receiver signal is amplified by a "video amplifier." After amplification of the signal is passed to implement the TRC. Without any signal applied to the cathode of CRT, it would be about 160V or so. The grid itself is at a lower voltage, because the grid is negative with respect to the cathode.
 
 
The black signal stops the flow of electrons towards the screen
 
If the signal received by the TRC is for a black, it will be a high voltage, since the camera dark tones produce high voltages. When high voltage is applied to the TRC, this will increase the tension over the 160V. This increased tension will cause the grid is more negative with respect to the cathode and therefore fewer electrons pass through the tube. Passing fewer electrons will have fewer crashes on the screen and therefore the phosphor screen will not emit much light. This results in a dark spot on the screen.
 
 
The target signal facilitates the flow of electrons towards the screen
 
By contrast, clear tones that produce a low voltage, when applied to the TRC, make the grid is not as negative as in the case of dark tones. Not being so negative the grid, it will be more electrons and therefore will impact more electrons on the screen, causing the phosphor emits more light. This results in a light color. This process we can imagine in a "gradual" for all shades and intensities of light. So we have a range of possible values ​​of stresses being applied to the TRC will be causing more or less clear tones, thus obtaining a range of hues, both black and white and color.
 
A very important factor to consider in capturing and displaying the image is the synchronism between the two. This implies that the frequency sweep RC pipe must be the same as the image capture on a camera, because, otherwise, the result could be chaotic. To achieve this synchronization has to give two conditions. First they have to do the horizontal sweep at the same speed, ie when the stream of TRC is ready to begin scanning a line, so is the camera. Similarly, both have to be in phase with the vertical scan so that when the electron gun to move into a new line, so do the barrel of the camera. When these two conditions can one speak of a synchronized mirror. If the picture is not synchronized vertically on the screen image appear moving vertically. An image that has no horizontal sync appear slightly tilted, oblique rays produced in a totally unrecognizable.
 
 
Typical image signal corresponding to a line of TV
 
To achieve the perfect synchronization, both horizontally and vertically, the issuer of the video signal, in addition to sending the signal, sends two types of pulses, horizontal sync pulses and vertical sync pulses. The horizontal sync are tensions in the form of square wave that the station broadcasts at the end of each line. This is made known to the receiver that the line has already been transmitted and, therefore, be passed to pass the next. Similarly, the vertical sync pulses are tensions in the form of square wave.
A very important factor to consider in capturing and displaying the image is the synchronism between the two. This implies that the frequency sweep RC pipe must be the same as the image capture on a camera, because, otherwise, the result could be chaotic. To achieve this synchronization has to give two conditions. First they have to do the horizontal sweep at the same speed, ie when the stream of TRC is ready to begin scanning a line, so is the camera. Similarly, both have to be in phase with the vertical scan so that when the electron gun to move into a new line, so do the barrel of the camera. When these two conditions can one speak of a synchronized mirror. If the picture is not synchronized vertically on the screen image appear moving vertically. An image that has no horizontal sync appear slightly tilted, oblique rays produced in a totally unrecognizable.Typical image signal corresponding to a line of TV To achieve the perfect synchronization, both horizontally and vertically, the issuer of the video signal, in addition to sending the signal, sends two types of pulses, horizontal sync pulses and vertical sync pulses. The horizontal sync are tensions in the form of square wave that the station broadcasts at the end of each line. This is made known to the receiver that the line has already been transmitted and, therefore, be passed to pass the next. Similarly, the vertical sync pulses are tensions in the form of square wave. These signals inform the receiver that it has finished transmitting a full screen and therefore now proceed to issue a new screen, starting again for the top corner. General scheme of a TVTrying to explain the workings of a TV element to element would be a somewhat laborious task because of the many elements that compose it. However, as in most electronic devices currently available, it usually gives a general scheme where blocks are grouped by the various components that make up for, well, simplify your understanding of its operation. This scheme is usually called "logic block" or "block diagram". In this representation, each block of the scheme generally consists of a number of resistors, capacitors, inductors, integrated circuits, etc.. Form a circuit. The function of this circuit is actually what you really want both from a pedagogical point of view and from a technical point of view. Let's look so different blocks that make up the TV. Block circuit diagram of a television receiver The "channel selector" has the mission to the channel to be displayed, in addition to amplifying the signal and obtain the intermediate frequency. The circuit comprises the channel selector is formed, therefore, a tuning circuit, an amplifier and an oscillator-mixer. Because the signal from the transmitter is a dual sign, as it is formed by the image signal and sound signal, the signal selector is intermediate signal will also double. The image carrier has a frequency intermediate frequency of 38.9 MHz while the sound frequency is 33.4 MHz frequencies are both unchanged and they are independent of the channel is tuned. Selector output signals The "intermediate frequency amplifier," as its name suggests, is a signal amplifier. Its mission is to amplify the intermediate frequency signal from the selector. This signal is received by a shielded cable. The circuit formed by this intermediate frequency amplifier usually consists of three stages of transformer coupled amplifiers tuned. The "detector" Video's mission is to detect the image signal, amplitude modulation, which comes from the intermediate frequency amplifier and gets the video signal with the sync down. In addition, the detector acts as a mixer image signal of 33.4 MHz and the picture carrier of 38.9 MHz, the latter acting as an oscillator, resulting in its output a new signal whose frequency is the difference between them, ie, 5.5 MHzThis signal has been modulated in frequency, such as 33.4 MHz from which proceeds, is called second sound intermediate frequency. Therefore, signals reach the detector image intermediate frequency (38.9 MHz) and audio signals (33.4 MHz) and leave the video signal and the signal of second sound intermediate frequency (5.5 MHz).The "video amplifier" amplifies the video signal is obtained in the detector. The video signal is thus amplified and inverted, ie to sync up, which is the correct way it should be applied to the cathode ray tube cathode. Sometimes we can find video amplifiers also amplify the video signal, also amplify the sound signal.The "5.5 MHz trap" prevents amplification of the audio signal of 5.5 MHz video amplifier. It acts as a filter. If, however, you want the video amplifier amplifies the signal, the trap is placed between the amplifier and said cathode ray tube. This will get the audio signal of 5.5 MHz from reaching the cathode ray tube as it would lead to interference from the overlap of both signals. The "sound channel" is the receptor responsible for managing the audio signal. The circuit that consists of an amplifier comprised of 5.5 MHz, a frequency modulation detector, a low frequency amplifier and, of course, a loudspeaker. In cases in which the video amplifier does not amplify the second intermediate frequency of sound, the sound channel amplifier offers two because, otherwise, the audio channel would have one. In any case, the amplified sound signal of 5.5 MHz is always done in two steps one of which may be the video amplifier itself. The mission of the FM detector is to obtain the low frequency signal, from the 5.5-MHz modulation frequency. The last element of the sound channel, the low frequency amplifier, preamplifier low frequency signal obtained and output stage attacks as a speaker. This is usually done through an output transformer.Block circuit diagram of the sweep veticalThe "pipe" is performed at a frequency of 50 Hz and is produced by a current of the same frequency through the coils of the deflection unit. This current is produced by an oscillator called oscillator or vertical picture. The signal produced by this oscillator is amplified through a vertical output stage. A transformer, output transformer called vertical or box, coupled to the sawtooth vertical deflection coils of the deflection unit. The "horizontal sweep" is obtained by a sawtooth current in a frequency of 15,625 Hz To achieve this often have a horizontal oscillator and a horizontal vent that is a stage to receive the signal with the help of current transformer produces a sawtooth.The "M.A.T." (Very High Voltage) is needed in the cathode ray tube. Its value may reach 18,000 volts. The purpose of this tension is to produce a greater acceleration of electrons flowing through the cathode ray tube towards the screen. In the transformer lines, responsible for the horizontal sweep, the sharp variation of the sawtooth intensity produced in the auxiliary windings of high voltage pulses. These impulses, whose value is about 18,000 volts are applied to the plate of a grinder MATThe "timing of sweeps," as already stated, is responsible for synchronizing the horizontal and vertical sweeps of the recipient with the corresponding scans of the station. This is possible because the station broadcasts at the end of each line a boost on the level of erasure to synchronize the horizontal oscillator of the receiver and the end of each display a train of 6 pulses to synchronize the vertical oscillator. The "spacer" is an entry that receives the video signal from video amplifier output and passes only the part corresponding to the sync pulses. This circuit sync separator is also known as the "clipper".The "integrator" is located below the sync separator. Get the impulses coming from the separator. Overrides the horizontal sync, and thus prevents reaching the vertical oscillator. When you receive the last of the 6 vertical sync pulses causes a voltage spike in its output. This drive produced, called integrated vertical sync pulse acts on the vertical oscillator forced to start a new sweep and keeping thus in phase with the vertical sweep of the station.
The "differentiator" is an element lying parallel to the integrator, ie behind the separator. As the integrator receives the impulses that come out of the separator, which are mostly horizontal. For each input pulse produces a signal at its output called differential drive. Therefore, each sync pulse becomes the differentiator in another drive called differentiated, consisting of a peak positive voltage and a negative voltage.
 
The "phase comparator" has the mission to create a control voltage of the horizontal oscillator to synchronize with the horizontal sweep of the station. To do this, the comparator receives the one hand the sync pulses and other differentiated two pulses one negative and one positive, created in the transformer lines in each horizontal retrace.The "valve reactor" acts on the horizontal oscillator to synchronize with the transmitter. This is necessary because the tension created by the comparator is applied directly to the horizontal oscillator but choke valve.The "AGC" is a voltage that is applied as a grid bias of the first two valves, intermediate frequency amplifier which controls in inverse proportion to the signal reaches the antenna. When the antenna signal is already strong, it also applies automatic gain control amplifier to the frequency selector in this case is called a delayed automatic gain control.
MATERIAL BAJADODELAPAJINA:http://www.angelfire.com/al2/Comunicaciones/Sistemas/tv21.html
The target signal facilitates the flow of electrons towards the screenBy contrast, clear tones that produce a low voltage, when applied to the TRC, make the grid is not as negative as in the case of dark tones. Not being so negative the grid, it will be more electrons and therefore will impact more electrons on the screen, causing the phosphor emits more light. This results in a light color. This process we can imagine in a "gradual" for all shades and intensities of light. So we have a range of possible values ​​of stresses being applied to the TRC will be causing more or less clear tones, thus obtaining a range of hues, both black and white and color. 

3 comentarios:

  1. caroline,el texto me parece muy bien hecho,pero te sugiero que le pongas imagenes, acuerdate de los link.

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  2. carolina, me parece muy interesante el texto ya que me informa mucho sobre los televisores no se mucho de ingles pero lo traduci, recuerda poner los link de la pagina de donde sacaste la información es muy importante.

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  3. Carolina, el tema sobre los televisores esta muy bueno aunque este en ingles entendí un poco sobre este trabajo :D

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