Jump into your couch, pick up the remote, point at the TV and press some two or three buttons. Voila! You’re already at your favourite TV station. It’s a routine we are used to, but thinking about it, it may seem like nothing short of magic. But is it really magic? Read on, as the answer lies in this short write-up. You’ll also discover a simple, safe and fun electronics experiment you can do at home, using components you already have!
Invisible light?
You’ve probably noticed that transparent spherical object at the top of your remote as can be seen in the picture below.
If you thought to yourself “that kinda looks like a light bulb”, you’re actually right! Specifically, it’s an LED (Light-Emitting Diode). But wait, if that’s the case then how come you haven’t ever seen it give off any light? Well, actually it does produce light (don’t panic, nothing wrong with your eyes). The reason you, nor I nor any other [normal] human cannot see the light from it, is because the kind of “light” it emits is infrared (IR), which is invisible to our eyes. Ironically though, the purpose of this article is to show you a way of seeing this “light” that is supposed to be invisible! Without further ado, let’s get straight to it!
Items Required
- Infrared Remote Control
- Smartphone (or laptop) Camera
See the invisible!
Open your smartphone (or laptop) camera app, direct it at the infrared LED of your remote control and press any button on the remote.
Surprised right? If everything goes as expected, you should see some flashing lights in the IR LED through the live camera feed with each button press. In all instances I’ve tried so far, the “invisible” light has a light-purplish colour through the camera feed. Let me know in the comments if you see a different colour. If you were to position the remote control and camera in such a manner that you can see both the IR LED directly with your eyes, and its image in the camera feed, you’d confirm that our naked eyes indeed cannot see the infrared light.
What’s happening?
This experiment works because unlike human eyes, digital cameras are often sensitive to infrared light as well. They usually have in-built IR-cut digital filters to prevent infrared light from distorting the images we take, but there is still enough room to allow us visualize the IR light output from our remote control, as in this case.
You might also have noticed that when a button is pressed on the remote control, the IR light does not stay on constantly, but it flashes or blinks. The reason for this is that the remote control communicates with the television (or other appliances) through a sequence of pulses of light, where each button on the remote generates a specific pulse sequence. The TV has a special infrared receiving sensor that is able to read and decode the sequence and initiate the expected action for that button. Think of this as a kind of Morse Code communication. As a rough example, a sequence of, say, “OFF-ON-OFF-OFF” may represent the “Menu” button on the remote, and another sequence “OFF-ON-OFF-ON” may represent the “Exit” button.
These are overly simplified examples for illustration purposes, but I hope you get the point.
Final Words
Next time your TV isn’t responding to your remote commands, you now know at least one method of troubleshooting. Just view the IR LED of your remote through a digital camera and press some buttons. If you don’t see any light, then the most probably cause is a drained battery. Replace the batteries and re-try the experiment.
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