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What is a Red Cathode?

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  • Written By: Mal Baxter
  • Edited By: Daniel Lindley
  • Last Modified Date: 02 November 2016
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Cathode technology appears in numerous lighting and screen display products; a red cathode refers to custom lighting technology called a cold cathode fluorescent lamp (CCFL). This is a type of fluorescent light bar that glows brightly and offers an eerie effect for lighting design applications. It is commonly found in the art of case modding, or the modification of computer cases with windows, fabricated cuts, and illuminated components. Unlike neon tubes, these lights use no heating filament and burn many times more brightly and reliably than incandescent bulbs. CCFLs may run on 12-volt inputs, minimizing amperage via an inverter, typically included with power supplies in ready-to-use kits.

A fluorescent lamp illuminates by generating high voltage between electrodes through mercury vapor; the resultant plasma arc emits ultraviolet radiation, which excites a phosphor-treated glass surface. The phosphor may be treated with colorants to produce wavelength-selected light transmissions. Additionally, acrylic tube housings intensify color types. The red cathode, however, a sought-after color, has proven notoriously difficult to obtain as a natural wavelength; many so-called red cathodes must be color corrected through the use of tinted sleeving or film. A preponderance of red cathodes that actually appear orange or pink has created a market for true red CCFLs.

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Red cathode CCFLs may obtain coloring through triband phosphor application, colored glass, or add-on filters. Cathodes provide compact size and low power consumption. Their dramatic lighting effects appear in signboards, interior decoration, and toys. These long-lived, reliable lamps come in various tube lengths and configurations, and can be customized to user specifications. Easy installation and added features, such as the ability to pulse with sound and music, make these lights an attractive component in varied applications of creative lighting.

Thinner, brighter, and longer-lived than neon tubes, red cathode lamps also have disadvantages. They may not reach maximum brightness until after some hours of use. Step up transformers provide the required voltage, which may introduce heat into their surroundings, typically a computer case. Faulty components or manufacturing processes could increase risk of failure and even fire. The ubiquitous availability of light-emitting diode (LED) products, by comparison, offers solid state operation at less voltage and amperage with comparatively less net heat, and these devices are readily available in numerous desirable colors, including true red.

A typical red cathode CCFL transmits light at a spectral energy distribution between about 570 to 700 nanometers (nm), with its mean at about 630 nm; that is, it's a wider and more yellowish bell curve on the light spectrum. One variation is the deeper, ruby red wavelength, with a distribution falling more narrowly between 620 and 700 nm, with a mean at about 650nm. Long, thin cathode tubes are easily concealed inside edges and nooks for dramatic effect, and inverters can connect with almost any 12V power source. With numerous advantages over neon and incandescent lighting, these lamps enhance cars, motorcycles, and more with dramatic, colorful illumination.

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