How They Work

“The Plasma Television” Since its inception, the majority of television sets have been built using the CRT (cathode ray tube) technology. In a CRT television, an electron gun fires a beam of electrons (negatively-charged particles) inside a large glass vacuum tube. The electrons excite phosphor atoms along the wide end of the tube (the screen), which causes the phosphor atoms to light up. The television image is produced by lighting up different areas of the phosphor coating with different colours at different intensities. The Cathode ray tubes produce crisp, vibrant images, but they do have a serious drawback in that, they are quite bulky; that greatly limits size of the TV Set. In order to increase the screen width in a CRT sets, you also have to increase the length of the tube (to give the scanning electron gun room to reach all parts of the screen). Subsequently, any huge-screen CRT television has to weigh a hundreds of kilograms and would occupy a sizable part of any room. As a result of the above, a new alternative has evolved up in the name of “The Plasma Flat Panel Display”. These modern televisions have wide screens, comparable to the largest CRT sets, but they are only about 6 inches (15 cm) thick. If you have read one of the previous articles on how TV works, then you should understand the basic idea of a standard television set. Using the information in a video signal, the television Set bombards up thousands of tiny dots known as pixels, with a high energy beam of electrons. In most systems, there are three pixel colours red, green and blue which are evenly distributed on the screen; combining these colours in different proportions, the set is able to produce the entire colour spectrum. Basically, plasma display illuminates tiny, coloured fluorescent lights to form an image. Each pixel is made up of three fluorescent lights, the red light, green light and blue light, almost like the CRT system does. However, the plasma display varies the intensities of light to produce a full range of colours. The main element in a fluorescent light is plasma, (a gas made up of free-flowing ions, electrically charged atoms) and electrons (negatively charged particles). Under normal circumstances, a gas is made up of uncharged particles. That is, the individual gas atoms include equal numbers of protons (positively charged particles in the atom’s nucleus) and electrons. The negatively charged electrons perfectly balance the positively charged protons, so the atom has a net charge of zero. If you introduce many free electrons into the gas by establishing an electrical voltage across it, the situation changes very quickly. The free electrons collide with the atoms, knocking loose the other electrons. With a missing electron, an atom loses its balance. It has a net positive charge, making it an ion. In plasma, with an electrical current running through it, negatively charged particles are rushing toward the positively charged area of the plasma, and positively charged particles are rushing toward the negatively charged area. In such a confused situation, particles are constantly bumping into each other. These collisions excite the gas atoms in the plasma, causing them to release photons of energy. (to be continued)eddie@afrowebs.com