LED

Updated: 03/06/2020 by Computer Hope
LED status lights

Short for light-emitting diode, LED is a semiconductor that illuminates when an electrical charge passes through it. LEDs are commonly green, amber, or red, but they can be an assortment of other colors as they've become popular with case lighting. Below are examples of how an LED could be used with a computer.

Keyboard LEDs

Keyboard light emitting diode or LED

An example of an LED is the led status indicators on your keyboard for Num Lock, Caps Lock, and Scroll Lock, as shown in the picture. The blue LED on the keyboard indicates the Num Lock is enabled, but since the Caps Lock and Scroll Lock LEDs are not, that indicates they are not enabled. The location of these indicators depends on the keyboard manufacturer. Most often they are in the top-center or top-right part of the keyboard.

How to turn and off the keyboard LEDs?

To turn on and off (enable and disable) the keyboard lights, press the Num Lock, Caps Lock, or Scroll Lock key on the keyboard. Keep in mind that the keyboard LED's are not the same thing as a backlit keyboard where all keys have a light behind them.

Note

Not all keyboard num lock, caps lock, or scroll lock indicators have identifiers like those shown in the picture. If you are not sure what LED goes to what key, press the Num Lock, Caps Lock, or Scroll Lock key while watching the LEDs and see which one illuminates.

Tip

Apple keyboards and some others have the Caps Lock LED indicator on the Caps Lock key and may not have other indicators because there are no Scroll Lock or Num Lock keys.

Mouse LED

Most computers today use an optical mouse, which is a mouse that uses an LED to help track the cursor on the screen.

Motherboard LED

Motherboard LED

Many motherboards have an onboard LED that lets users know the motherboard has power. The LED may also be used to let users know if there are errors. The picture is of an LED/PLED located between the PCI slots on a motherboard.

Note

Do not work inside a computer or disconnect any internal plugs while this LED is lit.

Tip

When the power cable is disconnected from the computer, the LED light stays on for several seconds and then slowly fades off, which is normal.

Network card, switch, and router LED

The LEDs on a network card, network switch, and network router indicate when a connection is made and when data is being transferred. For example, without a cable connected to a network card, it shows an orange LED or no LED. However, when a cable is connected, the LED lights up as a solid green LED. As the card is used (e.g., browsing the Internet), data is sent to and from the network card and the LED flashes to indicate communication.

Floppy, hard drive, CD-ROM, and other drives LED

Computer floppy drives and CD-ROM drives have front LED indicators to indicate that data either being read from or written to these media.

Hard drives have no LEDs on them. However, the motherboard sends signals through system panel connector cables, causing an LED on the front of a computer to flash when active.

Printer, speakers, monitor, and other devices

External devices that require power (e.g., monitor, printer, or speakers) also have an LED indicator to indicate when the device is on, off, or has an error.

Red, amber, green, white, and blue LED meanings

There are only de facto standards when classifying the meanings of an LED's color. Below are explanations of what an LED and its color may mean.

Solid green, blue, or white LED

Computer power button

A solid green, blue, or white LED on the front of a computer, monitor, or another device is often an indication of power. For example, when you press the power button on your computer, if the computer is getting power and is working, the light should illuminate and stay solid.

Blinking green, blue, or white LED

A blinking green, blue, or white LED is an indication that data is being transmitted or the device is working.

Tip

Most blinking LEDs, regardless of the color, are an indication that something is working, being processed, or that data is being transferred.

Solid amber or yellow LED

A solid amber or yellow LED often means the computer, monitor, or other device has power but is not getting a signal. For example, a monitor displays a yellow LED with no display or a black screen when the data cable is disconnected.

Blinking amber or yellow LED

Amber or yellow LEDs indicate that data is being transferred over a network card, modem, switch, or router. In the case of a router, this light may also blink so fast sometimes that it may appear to be solid.

Solid red LED

A red LED is often a method of notification or alert. For example, on a surge protector or UPS (uninterruptible power supply), a red LED indicates that surge protection is working and available.

Blinking red LED

A blinking red LED is often usually only used as an alert to notify the user that there is a problem.

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