Color Characteristics of LEDS

There’s an array of different LEDs that are available in the lighting market today. The diverse LED characteristics comprise of light color or radiation wavelength and light intensity among other features. 

These color characteristics are as a result of an assortment of factors during the manufacturing process. Factors such as semiconductor make-up, fabrication technology used, and encapsulation are also important in determining the LED color appearances.

Understanding LED colors

Color is a fundamental feature of light emitting diodes (LEDs). Initially, there were a limited number of colors available for these fixtures. You could only find red LEDs.
However, as technology advanced, there have been significant improvements in LED materials and colors.

Color Characteristics of LEDs: Color Temperature

One important aspect of color appearance is color temperature, which exemplifies how cool/bluish or how warm/yellowish technically white light appears. CCT Correlated Color Temperature (abbreviated as CCT), is actually a metric correlating the source of light appearance to a pre-heated theoretic dark/black body appearance. As a black-hued body gets hotter, it becomes red, orange, white, and ultimately blue. The CCT value of a light source, provided in Kelvin (K), represents the temperature at which a hot black body closely matches the light source color under investigation. It symbolizes the color of emitted light and not that of illuminated objects.

What is Color Rendering Index (CRI)?

Metrics Color representation has numerous distinct forms, including reference based systems, gamut based systems, and systems which are built upon sophisticated color appearance models.
CRI refers to a measure of fidelity (that’s how ‘true’ a certain light source is when related to a reference source), but it doesn’t address the issue of color appeal and discrimination.

Chromaticity and LED Colors

Chromaticity refers to an objective interpretation of the quality of color irrespective of its luminance. It consists of two distinct parameters, often described as colorfulness (s) and hue (h). For a specified CCT, a light source with a positive Duv value has a chromaticity which falls above the locus of the blackbody (appearing slightly greenish), while a source featuring a negative Duv value has a chromaticity which falls below the locus the blackbody (appearing slightly pinkish).

The Influence of LED voltage drops

The LED voltage drop often lies between 2 and 4 volts. The actual voltage that occurs across the two terminals is highly dependent on the type of LED/materials used and influences the color of LED in question.

As expected, the voltage curve of an LED broadly resembles that of a forward diode characteristic. But once the diode is switched on, the voltage becomes relatively flat for various forward current levels.

LED Characteristics: The Summary

The following table gives a summarized insight concerning LED color characteristics.

Wavelength Range In NM	Color Of the LED	Voltage(V) at 20MA	The Type of Material
Blow 400	UV(Ultraviolent)	3.1 to 4.4	AIN, AlGaN, AlGalnP
400 to 450	Violet	2.8 to 4.0	GaP,AlGalnP
450 to 500	Blue	2.5 to 3.7	lnGaN
500 to 570	Green	1.9 to 4.0	GaP, AlGalnP
570 to 590	Yellow	2.1 to 2.2	GaAsP, AlGalnP
590 to 610	Orange or Amber	2.0 to 2.1	GaAsP, AlGalnP
610 to 760	Red	1.6 to 2.0	AlGaAs, GaAsP, AlGalnP

Below 760

Infrared

Below 1.9

GaAs, AlGaAs

Besides LED color, the following are other major LED specifications:

• Light intensity value( denoted as Iv)

• Current vs. voltage specification

• Reverse voltage

• Angle of view

LED Specifications for Operational Life

LED’s light intensity doesn’t diminish with time. What this implies is that LEDs have a specific operational life. This specification helps determine the application of different kinds of LEDs. LED specifications are determined by the following formulas.

L70% = The time taken for a 70 percent illumination (this is also known as lumen maintenance)

L50% = The time taken for a 50 percent illumination (also known as lumen maintenance)

Note: According to LED standards, your LEDs shouldn’t exhibit any major shift in chromaticity.
These figures’ rationale is that 70 percent lumen maintenance is equated to a 30 percent light output reduction. This’s an approximate threshold figure required to detect to gradual light output reductions.

RAKO WIRED VS WIRELESS SYSTEMS

Introduction

Rako is one the leading lighting control systems which performance admirably against the competition Lutron and Control 4 but does benefit by being of lower cost and it is easier to install. This makes it an ideal choice for high end residential and commercial properties.
One of the key benefits of Rako is the wireless solution which makes it a first choice for retrofits to existing properties where the lighting wiring is in place but there is no automation.
The key element of lighting control is to be able to select lighting scenes for a space which are set at the push of a button which will dim all the different lighting circuits to a prescribed level in the room. Rako allows you to have between 2 and 7 lighting scenes dependent on the selection of the control panel. For example a RCM-100 will allow 7 scenes to be programmed and a RCM-070 4 scenes.

Typically the scenes can light different areas of the space and allow for relaxation or for working by setting the light levels to the appropriate setting.

The Wireless Dimmers.

The RMT500 wireless dimmer is a trailing edge dimmer unit which has compact proportions and accordingly can be slipped up into the ceiling void through down-lighter holes. This means the converting a conventionally wired property to lighting control is straightforward and the existing wiring can normally be used. As the control panels are wireless these can then be positioned in place of the existing light switches or alternatively placed elsewhere in the room as no switch wiring is needed. The RMT500 is a very versatile dimmer which works very well on good quality LEDs anb depending on the back load of the LEDs can operate up to 500 watts of load. For larger loads the RMT1200 is a preferred choice as this can handle loads up to 1200w. There are leading edge dimmers available as well which are often better for incandescent or dimmable fluorescent loads. More details on the dimmer please take a look here RMT500.

Benefits if the Wireless System

• Good for retrofits and no switch wires needed
• Lower cost of control panels
• Extra control panels can be easily introduced at a late stage as no wiring needed

Wired Systems

For a wired system the RAK4 dimmers would normally be used, typically the RAK-4T which is a 4 channel trailing edge dimmer. These are normally located in a control room and all the lighting circuits would be run back to this room. The RAK-4T will take 4 channels but these can be linked together with a RAK-LINK to allow up to 8 RAK-4T dimmers to be connected together.

The other element of the wired system is the control panels. With the wired system then the control panels typically the WCM-070 would be daisy chained together with CAT5e cabling. If it is more convenient then a RAK-STAR can be used which means the control panels can be star wired from the control room.
However it is still possible to utilise the wireless control panels with the RAK system. This is done by introducing a RX-Link which allows wireless devices for instance control panels, to be connected into the Rako RAK dimmers.

Benefits of Wired System

• No batteries needed for control panels
• Control panels have back lit buttons for ease of viewing in the dark
• Programming easier where it is desired to control lighting is different rooms from certain control panels
• No limitation on RF signal strength and no distance limitations