One LED, Seven Colors? Master the “Primary Colors of Light” with This Palm-Sized Experiment!
I’m Ken Kuwako, your science trainer. Every day is an experiment!
Think about the dazzling light shows in the night sky or the smartphone screen you’re looking at right now. They are incredibly vibrant, but did you know that all those colors are created by combining just three simple colors? Today, I’d like to introduce a fascinating electronic component that lets you experience this “light magic” right in the palm of your hand.
A Magic Light Bulb? The “RGB LED” That Shines in Three Colors
I recently picked up some RGB LEDs, which pack three different types of light-emitting diodes into a single tiny package. While they look like ordinary LEDs at first glance, their most striking feature is the number of “legs”—they actually have four!
5mm RGB LED Common Cathode 4-Pin (Amazon)
The longest leg is the anode (positive terminal), while the other three legs are responsible for Red, Green, and Blue light. Let’s try lighting them up one by one using a 3V button battery.
A passionate Red glow.
A very vivid Green light.
A deep, cool Blue hue.
These three are known as the “Three Primary Colors of Light.” By mixing them in different ways, we can recreate almost every color in the visible world.
The Mixing Experiment: Theory vs. Reality
I couldn’t wait to see what happened when I mixed them, so I started connecting multiple legs to the battery at once.
First, Green and Blue.
The overlap created a beautiful Cyan (light blue)!
Next, Red and Green. Theoretically, this should give us yellow, but…
It looks more like a warm Orange than a pure yellow.
Finally, Blue and Red. I was expecting “Magenta (purple),” however…
The Red completely dominated the mix! There’s hardly a trace of purple here.
Decoding the “Personality” of LEDs: Why the Color Imbalance?
Our experiment revealed an interesting challenge: “The Red is too strong.”
As it turns out, LEDs have different “forward voltages” (the voltage required to start glowing) depending on their color. Generally, Red LEDs are very efficient and glow brightly even at low voltages. In contrast, Blue and Green LEDs require a bit more “push” (higher voltage) to reach their full potential. When connected to the same 3V battery, the current rushes into the Red diode, causing it to overpower the others.
To fix this, you would need to add a resistor to the Red leg to throttle the current slightly. This kind of “fine-tuning for individual characteristics” is exactly how we achieve perfect whites or purples in professional displays.
The world of the primary colors of light is contained within a single LED. It’s a wonderful teaching tool that doesn’t just “light up”—it makes you think about the physics behind the colors we see every day. Next time you see a glowing screen, take a moment to imagine the tiny Red, Green, and Blue dance happening behind it!
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