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. 

martes, 2 de agosto de 2011

feria de la ciencia

feria de la ciencia

Experimento huevo flotador

Un huevo se hunde hasta el fondo si se te cae en un vaso de agua potable ordinaria, pero ¿qué pasa si se agrega la sal? Los resultados de este experimento casero son muy interesantes y puede enseñarle algunos datos divertidos acerca de la densidad.
     
Materiales del experimento del huevo flotador:

  •     Un huevo
  •     Agua
  •     Sal
  •     Un vaso de altura




Preparación del experimento:


   1. Vierta el agua en el vaso hasta que esté lleno hasta la mitad.
   2. Revuelva en un montón de sal (aproximadamente 6 cucharadas).
material bajado de la pagina:
www.fullexperimentos.com

Punto ciego

La retina es el tejido nervioso que recubre la parte de atrás del ojo. Sobre ella se forman las imágenes que nos dan la sensación de visión. Está formada por unas células especialmente sensibles a la luz llmadas conos y bastoncillos. La retina está conectada al cerebro por medio del nervio óptico. El punto en el que éste se une a la retina se denomina punto ciego porque no tiene células fotosensibles (sensibles a la luz).
Normalmente no percibimos el punto ciego ya que al ver un objeto con ambos ojos la parte del mismo que llega sobre el punto ciego de uno de ellos, incide sobre una zona sensible del otro. Si cerramos un ojo tampoco seremos concientes de la existencia del punto ciego debido a que el cerebro normalmente nos engaña y completa la parte que falta de la imagen. Esta es la razón de que no fuese conocida la existencia del punto ciego hasta el siglo XVII.

Un experimento para comprobar la existencia del punto ciego

  • En una cartulina dibuja una cruz y un círculo como se ve en la siguiente figura:
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  • Coloca la cartulina a unos 20 centímetros del ojo derecho.
  • Cierra el izquierdo, mira la cruz con el ojo derecho y acerca lentamente la cartulina.
  • Llegará un momento en que el círculo desaparecerá del campo de visión. En este momento su imagen se forma sobre el punto ciego.
  • Al seguir acercando la cartulina, el círculo vuelve a aparecer.                                               material bajado de la pagina:
  http://www.cienciafacil.com/

LA INDEPENDENCIA

Independencia de Colombia

Independecia de Colombia - Casa del FloreroEn Julio de 1.810 se produjo en Santa Fe un alzamiento detonado por motivos más bien triviales, cuando los hermanos criollos Francisco de Paula y Antonio Morales Galavís fueron a la casa del español José González Llorente a que les prestara un florero para adornar una mesa en que se serviría un banquete a don Antonio Villavicencio, comisario del rey que llegaba a Santa fe de Bogotá.

El español insultó a los criollos, el pueblo se enfureció y estos le dieron una paliza, y se organizó una Junta Suprema de Gobierno del Nuevo Reino de Granada, dirigida por los Criollos, que llevó a declarar Cabildo Abierto, a deponer al Virrey y a suscribir un Acta de Independencia, replicada en otras capitales y en las provincias.

En muchas ciudades empezaron a aparecer juntas que no buscaban independencia sino autonomía con respecto a España. Sin embargo, los criollos terminaron por cambiar de opinión. La proclamación de independencia formal se inició en Venezuela el 5 de julio de 1811, mientras que en la Nueva Granada, debido a la división interna que sufría, se fue realizando de manera gradual, siendo Cartagena la primera provincia en proclamar la independencia el 11 de noviembre de 1811.

El 16 de julio de 1813 siguió su ejemplo Cundinamarca y posteriormente Antioquia, Neiva y Tunja. Las independencias de estas provincias dieron inicio al primer periodo de vida independiente de la Nueva Granada, llamado Primera República, pero también conocido como Patria Boba. El origen de este nombre se debe a las dificultades que enfrentaron los criollos para lograr el gobierno del territorio y que desembocaron en una guerra civil.

Esta primera guerra civil, con la que surgió la nación, tuvo un elemento político de trasfondo: el enfrentamiento entre quienes, como Antonio Nariño, pugnaban por un gobierno centralista y los que defendían el federalismo, como Camilo Torres. Mientras en la América hispana se luchaba por la independencia, en Europa, después de la derrota definitiva de Napoleón Bonaparte en 1814, hace que Fernando VII sea repuesto en el trono español.

Independencia de Colombia - Rey Fernando VIIEl monarca no se aviene a forma alguna de negociación con las antiguas colonias y se inicia la Reconquista , para eso encomendó a Pablo Morillo, quien al mando de un ejército de más de 10.000 soldados emprendió su campaña militar por Venezuela en 1815. La rápida victoria que logró en Cartagena le permitió iniciar el sometimiento del interior de la Nueva Granada.

La reconquista se facilitó en muchas regiones porque los pobladores estaban agotados por la guerra civil. En poco tiempo, los españoles volvieron a dominar el territorio granadino, con excepción de los Llanos Orientales, donde empezó el desarrollo de la tercera etapa del proceso de independencia. Tras la reconquista, vienen la cárcel o el fusilamiento de los líderes granadinos y el exilio de Bolívar en Jamaica.

Mientras Santander reorganiza en los llanos de Casanare un nuevo ejército y Páez combate en el Apure, Bolívar obtiene ayuda del régimen independiente de Haití para embarcarse de regreso, pero fracasa.

Luego con el apoyo de algunos soldados franceses y de Inglaterra, nación que aportó armas, dinero, municiones y un ejército de cinco mil hombres conocido como la Legión Británica, reinicia la guerra en el Orinoco en l.817, unificando alrededor de Bolívar el mando. Deja a Páez en Venezuela y en compañía de Santander emprende la etapa final de la independencia,  combatiendo a los españoles en la batalla definitiva del Pantano de Vargas, de la que José María Barreiro, jefe de las tropas españolas, salió debilitado. La victoria criolla fue posible gracias a la decidida participación del comandante Juan José Rondón, quien al mando de 14 lanceros atacó en el preciso momento en que los realistas estaban a punto de ganar la contienda.

Independencia de Colombia - Libertador Simón BolívarLa victoria en la Batalla de Boyacá, el 7 de agosto de 1819 selló la derrota definitiva del ejercito español. Días después, el ejército patriota entró en Bogotá, mientras que las tropas españolas buscaban huir a Cartagena o al sur del país. Esta batalla abrió paso para que se llevaran a cabo las campañas libertadoras de Venezuela, Quito, Perú y alto Perú.

En Diciembre de ese mismo año se crea en Angostura La Gran Colombia, formada por lo que habrían de ser luego Colombia (que comprendía entonces a Panamá), Venezuela y Ecuador, parcialmente aún bajo el dominio español. El nuevo país, con capital en Santa fe de Bogotá, quedó al cuidado del Vicepresidente Santander, mientras Bolívar proseguía la guerra.

En España, entre tanto, el reinado de Fernando VII hace crisis: el amotinamiento de Riego impedirá el zarpe de nuevas fuerzas de apoyo a la Reconquista, acelerándose así la liberación de los territorios que permanecían bajo control de la Corona. Morillo regresa a España en l.821, dejando un ejército maltrecho. San Martín, desde el Mar del Plata, ascendía victorioso hacia el Perú, donde Bolívar consigue la expulsión definitiva de los españoles en l.824. Sucre (venezolano) y Córdoba (granadino), fueron los héroes principales de la última fase de la contienda, en cuya provisión material Colombia asumió los suministros y la mayor parte de la deuda contraída con los ingleses.

El sueño bolivariano de mantener unidas las ex-colonias hispánicas tuvo un intento fallido en el Congreso Anfictiónico de Panamá (l.826). Ni siquiera la unidad de las tres naciones socias iniciales de la Gran Colombia prosperó: primero el caudillismo de Páez en Venezuela, y luego el de Flores, en Ecuador, la liquidan. Bolívar muere en Santa Marta en l.830, repudiado por sus compatriotas venezolanos y combatido en Colombia por una generación de jóvenes civilistas, contrarios a la dictadura.