Here is a list of things LED´s can and are used for:
Lighting
Light bulbs
Lanterns
Streetlights
Large scale video displays
Architectural lighting
LED-based Christmas lights
Motorcycle and Bicycle lights
Flashlights, including some mechanically powered models.
Emergency vehicle lighting
Grow lights composed of LEDs are more efficient, both because LEDs produce more lumens per watt than other alternatives, and also because they can be tuned to the specific wavelengths plants can make the most use of.
Backlighting for LCD televisions and displays. The availability of LEDs in specific colors (RGB) enables a full-spectrum light source which expands the color gamut by as much as 45%.
Stage lights using banks of LED’s as replacement for incandescent bulbs. LED’s produce less heat so LED stage lighting is cheaper to operate and reduces the risk of fire considerably.
Light source for machine vision systems, requiring bright, focused, homogeneous and possibly strobed illumination.
Indicators and signs
Status indicators on a variety of equipment
Traffic lights and signals
Exit signs
Railroad crossing signals
Continuity indicators
Elevator push-button Lighting
Thin, lightweight message displays at airports and railway stations, and as destination displays for trains, buses, trams, and ferries.
Red or yellow LEDs are used in indicator and alphanumeric displays in environments where night vision must be retained: aircraft cockpits, submarine and ship bridges, astronomy observatories, and in the field, e.g. night time animal watching and military field use.
Red, yellow, green, and blue LEDs can be used for model railroading applications
In dot matrix arrangements for displaying messages.
As a medium quality voltage reference in electronic circuits.
Other interesting Applications
Devices, medical applications, clothing, toys
Remote controls, such as for TVs and VCRs, often use infrared LEDs.
Glowlights, as a more expensive but longer lasting and reusable alternative to Glowsticks.
Movement sensors, for example in optical computer mice. The Nintendo Wii’s sensor bar uses infrared LEDs.
In optical fiber and Free Space Optics communications.
Toys and recreational sporting goods, such as the Flashflight
Lumalive, a photonic textile .
In pulse oximeters for measuring oxygen saturation.
LED phototherapy for acne using blue or red LEDs has been said to significantly reduce acne over a 3 month period.
Some flatbed scanners use an array of red, green, and blue LEDs rather than the typical cold-cathode. fluorescent lamp as the light source. Having independent control of three illuminated colors allows the scanner to calibrate itself for more accurate color balance, and there is no need for warm-up.
Computers, for hard drive activity and power on. Some custom computers feature LED accent lighting to draw attention to a given component. Many computer manufacturers use LEDs to tell the user its current state. One example would be the Mac, which tells its user when it is asleep by fading the LED activity lights in and out.
Sterilization of water and other substances using UV light.
