Rob: From the response we got about last month's "Special Effects" episode of B.Y.O.PC, we're taking some extra time to go over the technologies that allow us to make our computers glow.

Chris: One of the latest trends for Build Your Own Systems is case lighting. While stylized cases, cases with windows, and transparent cases may be interesting, the addition of specialty lighting makes them eye-catching. Keep in mind that what you can do on your own far surpasses what the industry's computer vendors can produce, mostly because of FCC restrictions on (finished) electronic products.

Rob: What do FCC regulations have to do with computer cases?

Chris: Cutting holes in the case to view the pretty lights does nothing to improve the radio-frequency blocking characteristics of a sheet-metal liner or metal case. For a company to sell a complete FCC-approved system with windows and internal lighting effects, it would require special metal-shielded windows that are electrically connected to the grounded chassis. But that is a whole different article that we can address at another time.

Rob: Got it. The case of a computer keeps the signals that are bouncing around inside from getting outside and wreaking havoc on all sorts of wireless doohickies.

Chris: That's right Rob. You wouldn't want to sacrifice your wireless networking connectivity for lights, no matter how pretty they might be.

Rob: I've seen lots of different lights in some really cool set-ups. What types of lighting are there?

Chris: Case lighting enhancements can be organized into three basic categories. These include Light Emitting Diodes (LEDs), Cold-Cathode Fluorescent Tubes (CCFT) and neon, and Electro-Luminescent (EL) technologies. A possible fourth category might be ultraviolet, special cables and glowing plastic motherboard connectors will fluoresce, but only with a UV light source which is typically going to be LED or cold cathode in nature.

Light Emitting Diodes (LEDs):

LEDs that have their light directed into a diffusing rod or sheet are a low-voltage alternative to neon or electro-luminescent lighting.

By combining more than one color of LED device into a single package, you can have LEDs that produce different colors depending on the direction of the current. These are commonly used as system power indicator LEDs, since they can be green when on, yellow in standby mode and red in hibernation mode. LEDs are also used to show system diagnostics, power, and system standby status. One purpose of these LEDs mounted on your system board is to remind you that just because the system is "off", it does not mean that it does not have power! Along the lines of the system diagnostic LEDs, is memory with built-in status indicators - Corsair makes memory modules that constantly display memory access and activity while the computer is running.

LEDs that have their light directed into a diffusing rod or sheet are a low-voltage alternative to neon or electro-luminescent lighting.

By integrating a tiny green, red and blue LED component into a single package, manufacturers can produce a "white" LED. By adding additional circuitry to this package, you can have a small LED size package that can cycle through the whole color spectrum or display different color or blink patterns.

LEDs have the advantage that they use very little power, yet can be quite bright in terms of illumination. A disadvantage is that they generally only provide small point-source directional lighting unless a diffusing rod or panel is used. LED illuminated fans are probably the most popular addition, with the spinning blades catching the light in a shimmering pinwheel effect. By using ultraviolet LEDs and fluorescent tinted plastics, UV fans can have contrasting or complementary color schemes to match your case or system board.

Left: A blue LED case fan. Center and Right: a UV case fan with two different colors of fluorescent plastic.

Cold Cathode Fluorescent and Neon:
Fluorescent and neon lighting both use a rigid glass tube containing a low-pressure gas and two electrical contacts. When high voltage power is applied between the connections, the gas ionizes and begins to glow. The name "cold cathode" is based on the principle that the light given off by these bulbs is not from super-heating a wire filament to white-hot incandescence. Although fluorescent and neon tubes produce light with very little heat, there is still some heat produced by both the lamp and the power inverter that is converting 12 volts into several hundred volts necessary to drive these bulbs.

Clear tubes generally can produce only one of two colors, orange-red from neon gas, or blue from mercury vapor (usually mixed with argon). To achieve an extremely wide variety of possible colors, a phosphor coating is applied to the internal surface of the glass tube. Besides the natural red or blue glow, ultraviolet light is also produced by both of the gas types, and this causes the phosphor coating to glow. Common fluorescent bulbs use this technique to produce a relatively cool-to-the-touch white light. By using tinted glass or a transparent color coating over the tube, subtle shades of colors can be obtained, or most of the visible light can be blocked, passing only the blue-violet and ultraviolet light.

From top to bottom: a multi-color "Spiral Liquid Cold Cathode Light" with red, green and blue phosphor; a green cold cathode fluorescent tube; a yellow-tinted (white) cold cathode fluorescent tube, and a pink cold cathode fluorescent tube.

Other Special Effects: By expanding the diameter of the containing tube, the ionized gas can be seen to randomly weave along the length of the tube between the contacts. This effect can be enhanced by dusting the inside of the clear glass with phosphor. As the gas passes near the coating, the phosphor glows brightly in a specific color. By coating different sections of the tube with different phosphors, multiple colors within the same tube can be produced. By filling the tube with small glass chips, a jagged lightning effect can be produced as the ionized gas zigzags between the beads.

Cold cathode fluorescent lights add bright illumination to any case with a minimal amount of additional heat.

Electro Luminescent:
Electro luminescent is available in a variety of forms including wire, strip or ribbon, and flat sheets. As with most cold cathode fluorescent tubes, electro luminescent lighting also uses glowing phosphor to produce light. The difference is that there is no rigid glass tube, and no ionized gas directly causing the glow. EL products generally operate at much lower voltages than CCF or neon, usually around 100 volts. EL products are made up of two conductive layers with an electro-luminescent phosphorus layer sandwiched between them. When a charge is applied between the two conductors, the phosphor layer will glow. Electro luminescent products are available in a variety of colors, although most are achieved by color-tinting the plastic that covers the white or blue-green glowing phosphor.

Cables can be purchased with electro luminescent wire already sealed inside the insulated sheath, which is probably better than running EL wire around unshielded data cables. In the case on the right, I wrapped the last foot of EL wire around the power cables running from the drives.

	While not as bright as a cold cathode solution, electro luminescent wire and logos can be run almost anywhere inside your case, even wrapped around the wire bundles.
	Electro Luminescent materials are available in wire, ribbon and sheet forms and in a variety of colors.

EL wire uses a central copper wire as one conductor that is coated with a layer of phosphor, then wrapped with one or two very fine wires for the second conductor. Then wire is coated with a clear or color-tinted sheath that serves to insulate, adjust the color, and protect it from moisture.

EL ribbons and sheets start with either a foil or metallic-coated plastic layer which is coated with the phosphor, and finally, sealed with a transparent film that has a microscopic metallic coating for the front conductive layer. This top plastic coating provides the second electrical contact and may also be tinted to shift the apparent color of the phosphor. Items such as the EL logos may have the phosphor coating laid down only where the necessary sections are to be illuminated, or the effect can be achieved by an opaque mask on the surface layer.

Electro luminescent wire can be taped, clipped, or just wrapped around your wire bundles for a unique lighting solution. To achieve a very straight line with EL wire without using clips, run it through lengths of clear plastic tube. Tip: check out pet stores for rigid clear tubing used for aquarium air lines.

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