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Computer Case Modding

Case modding is the artistic modification of a computer chassis (often just refered to as the case), often also involving peripheral components. Many people, particulary hardware enthusiasts use case mods to illustate a computers power. The terminology "mod" is short for "modification."

Computer Cases History

When personal computers hit the mainstream, most of them came in a case in the color of beige. This functional design was often called a beige box Although this served the purpose of containing the components of a personal computer, as time wore on, many users found their computers to be "tacky" or "dull" due to the lack of originality in the case design. So to solve this, some users began to modify their existing chassis or build their own.

Later, Case Modification became mainsteam when the Apple iMac was released, which went against the beige box design around at the time. Since then many computer manufacturers began selling cases that lack the dull beige base color. Case Modification has also opened up a new market for 3rd party computer cases to continue the break from the average case. Beige cases are now becoming harder to find since users enjoy the larger variety of colors and styles of current OEM cases.

LED technology and Computer Modding: Things you should know when lighting your computer

Physical function
An LED is a special type of semiconductor diode. Like a normal diode, it consists of a chip of semiconducting material impregnated, or doped, with impurities to create a structure called a pn junction. Charge-carriers - electrons and holes flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon as it does so.

LED Light emission
The wavelength of the light emitted, and therefore its color, depends on the bandgap energy of the materials forming the pn junction. A normal diode, typically made of silicon or germanium, emits invisible far-infrared light, but the materials used for an LED have bandgap energies corresponding to near-infrared, visible or near-ultraviolet light.

Considerations in use of LED lights in computer cases
Unlike incandescent light bulbs, which can operate with either AC or DC, LEDs require a DC supply of the correct electrical polarity. When the voltage across the pn junction is in the correct direction, a significant current flows and the device is said to be forward-biased. If the voltage is of the wrong polarity, the device is said to be reverse biased, very little current flows, and no light is emitted. Most LEDs have low reverse breakdown voltage ratings and will be damaged by an applied reverse voltage of more than a few volts.

Because the voltage versus current characteristics of an LED are much like any diode, they can be destroyed by connecting them to a voltage source higher than their turn on voltage. A good LED driver circuit is either a constant current source or an approximation to a current source made by connecting the LED in series with a current limiting resistor to a voltage source. The voltage drop across a forward biased LED can change significantly based on current flow.

Parallel operation is generally problematic. The LEDs have to be of the same type in order to have a similiar forward voltage. Even then variations in the manufacturing process can make the odds of satisfactory operation low. For more information see Nichia Application Note (http://www.nichia.co.jp/specification/appli/electrical.pdf).

Some LED units contain two diodes, one in each direction (that is, two diodes in inverse parallel) and each a different color (typically red and green), allowing two-color operation or a range of apparent colors to be created by altering the percentage of time the voltage is in each polarity. Other LED units contain two or more diodes (of different colors) arranged in either a common anode or common cathode configuration. These can be driven to different colors without reversing the polarity. --- Paul LoIacono is the president and owner of ATX Cases. You can see a wild array of computer case shapes, sizes and designs by visiting http://atxcases.com.

Paul LoIocano