How Do LED Lights Change Color?

Gone are the days of using lighting gels to change the color of a light source. Nowadays, one small diode is enough to supply an endless amount of colors.

But what is it about LEDs, in comparison to traditional bulbs, that allows them to change color? How can something so technologically advanced be so small?

A color-changing LED contains 3 separate diodes within the same bulb casing. Each of these diodes emits its own, specific color – red, green, or blue. When all three diodes are switched on at full capacity, white light is produced. Adjusting the intensity of each diode allows a range of different colors and shades to be created.

Colored LEDs are all around us. As well as decorative applications, they’re being used for communication and indication purposes. Just look at the Amazon Echo!

Want to know more? Then let’s get started. In this blog, I’ll be talking about how colored LEDs work, whether you can change the color of your existing LEDs, and how color differs from color temperature.

The Difference Between Color and Color Temperature

color temperature
Flexfire LEDs, inc., Brenton Patrick Mauriello [CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)]
Before I dive in, it’s worth clarifying what I mean by color, and how this differs from color temperature.

‘Color’ refers to the color of light that the diode emits – this can be any color of the rainbow. Color temperature, whereas, refers to the shade of white light emitted. White lights can produce warmer or cooler visual effects, and this is measured in degrees Kelvin.

The Kelvin scale was established by a British physician, Lord Kelvin, who researched color changes in heated metals. He found that as the temperature of a black material increases, its color changes from red to yellow and eventually blue.

Unlike air temperature, measured in Celsius or Fahrenheit, warm color temperatures have low Kelvins, and cool color temperatures have high Kelvins. The Kelvin scale runs from 0 – 10,000K, but most LEDs will be between 2,000 and 6,500K.

How Does LED Change The Color?rgb concept

LEDs can generate up to 16 million colors. So how do they work?

Colored LEDs are made up of 3 diodes: red, green, and blue (RGB). The RBG concept is an additive model, these colors are used because our eyes see all colors as different combinations of red, green, and blue wavelengths.

To create colored diodes, manufacturers of LEDs use different semiconductor materials for each diode.

The semiconductor in red diodes is most commonly made from aluminum gallium arsenide. Green diodes, whereas, use gallium phosphide and blue diodes to use indium gallium nitride.

Passing a current through all 3 diodes at equal intensity produces white light. Since LEDs are so small and the diodes are so close together, our eyes see the combination of colors, rather than each individual colored diode.

By adjusting the current so that it only flows through 2 diodes, an additional 3 colors can be created. Passing a current through the red and blue diodes creates magenta, red and green make yellow, and blue and green produces cyan.

Here is the table that represents the main color outputs you will get by mixing different colors.

Red

Green

Blue

LED Color

White

Red

red

Green

green

Blue

blue

Magenta

magenta

Yellow

yellow

Cyan

cyan

 

Alternating The Current To Each RGB Stream

Beyond this, other colors are created by adjusting the level of current running through each diode. If, for example, the red and green diodes are switched on but the green is running at 50%, a color between red and yellow will be created. In this case, orange.

By alternating current flow to each of the diodes, you can achieve over 16 million colors and shades.

Yes, all that by mixing just three primary colors.

In color changing LEDs, a microcontroller is used to control whether each diode is switched on or off. To dim a diode, whereas LEDs use Pulse Width Modulation (PWM).

As the name suggests, PWM works by rapidly turning the diode on and off. This flickering is so fast that it is undetectable to the human eye. Hence, our eyes only see the net result i.e., the color.

Most LEDs flicker at 1000Hz, but the human eye can only identify flickers slower than 200Hz.

To quantify the intensity of each diode, the RGB model uses a color code. You’ll probably be familiar with this if you have experience in graphic design or web development.

Under the RGB color code, each diode is given a decimal value between 0 and 255. So the color code for orange, to follow on from the earlier example, would be 255, 128, 0. This can also be presented in percentage form, 100%, 50%, 0%.

How Does LED Change The Color Temperature?

All in all, adjusting the color of an LED is fairly simple, but can the same be said for changing the color temperature of a bulb?

Unfortunately, it’s not that easy. LEDs are manufactured to produce specific Kelvin colors, which means once they’re constructed, the color temperature is fixed and cannot be changed.

As I discussed in a recent article, warm lights have a relaxing impact, and blue lights help to keep us alert. So this is frustrating, as some areas of the home are used for both relaxing and concentrating. You cannot have the best of both worlds.

Luckily, manufacturers have come to appreciate this situation and have innovated LED fixtures with changing color temperatures. These fixtures combine two sets of LED chips, cool and warm temperatures, which users can alternate between.

Take a look at this video by SIRS-Electronics to get a better understanding of how temperature-changing LEDs work:

Can You Alternate Colors Of The Bulb?

Despite the technology being relatively simple, color-changing LEDs are difficult to customize. Let’s break it down.

Firstly, there are two types of color LEDs: single and multi-colored. If a LED is always going to be a fixed red color, for instance, it would be wasteful to include the green and blue diodes inside the casing. Since they would always be switched off.

This means it’s physically impossible for single color LEDs to change color because they don’t have the required components.

Alternatively, most colored LEDs will contain all three primary colored diodes. They may be able to cycle through a variety of colors, but combinations will be predetermined by the LEDs manufacturer.

The color that light can emit is controlled by a small on-board computer. Unless you have access to this computer, it’s unlikely that you will be able to customize the colors of your LEDs.

Nevertheless, over the past year, smart LEDs have surged in popularity. This innovative technology allows you to control the color of LED lights via remote control or smartphone app.

Final Words

There you have it, the technology behind color-changing LEDs is surprisingly straightforward.

This color effect is specific to LEDs, and cannot be applied to traditional halogen or incandescent light bulbs.

So it’s no surprise that LEDs are becoming increasingly popular and are gradually being integrated into a whole array of devices.

What’s your opinion on colored LEDs – will you be introducing them to your home or keeping them in the loft with the Christmas and Halloween decorations?

Let me know in the comments below!

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