Remote Controls: Invisible Light

Here is a magic trick you can do right now:

1. Open the Camera app on your smartphone.
2. Take your TV remote. Point the front LED at the camera lens.
3. Press a button.

On your phone screen, you will see a flashing purple/blue light. Look at the remote with your naked eye. Nothing. Darkness. This is Infrared (IR) Light. It sits just below Red on the electromagnetic spectrum (lower frequency), meaning human eyes can’t detect it—but digital camera sensors can.

How Your TV Knows “Volume Up”

The remote isn’t just turning a light on like a flashlight. It is Blinking rapidly. It sends a binary code (Morse Code made of light).

• Volume Up: 101101 (Blink… Pause… Blink-Blink…)
• Power: 110011 The TV has a receiver that watches for these specific blink patterns.

Robotics and the Invisible Spectrum

Robotics teams use IR constantly because it is a reliable, invisible way to measure the world without cluttering the visual spectrum.

1. Distance Sensors (Time of Flight)

We use sensors like the REV 2m Distance Sensor.

• It fires a tiny laser pulse of IR light.
• The light hits a wall and bounces back.
• The sensor measures how long the round trip took.
• Since the speed of light is constant, Distance = Time / 2. This happens millions of times a second, allowing the robot to know “I am 10cm from the wall” with millimeter precision.

2. IR Beacons (Localization)

In older FTC games, the goals emitted an IR signal. Robots aimed for the invisible light to score autonomously. It’s like a lighthouse that only robots can see.

3. Break Beams (Intake Logic)

We put an IR emitter on one side of our robot’s intake and a receiver on the other.

• Empty: The beam connects. The robot knows it’s empty.
• Full: A game piece blocks the beam. The connection breaks.
• Action: The robot code says If (Beam Broken) { Stop Intake Motors; Close Claw; } This creates “Smart Intakes” that automate the grabbing process.

Why Not Use Visible Light?

Because the world is too bright. If your sensor relied on “White Light,” the massive stadium lights in a competition arena or a camera flash would confuse it. By using Infrared—and modulating it at specific frequencies like 38kHz—the robot can ignore the sun, the lights, and the crowd, and only listen to the specific “Secret Channel” it cares about.