How does an infrared remote work?

Infrared remotes. If you’re like me, you have a bucket of them dating back 15 or 20 years. I hate to get rid of a remote, I don’t know why, but somehow I think that I’ll need that VCR remote from 1993, although I’m not sure what I’ll actually need it for.

Did you ever sit down and think about what an infrared remote does and how it works? It’s not actually terribly difficult to explain, but once most of use get past the idea that there’s some sort of invisible beam, the explanations begin to dry up. Infrared remotes are miracles of both simplicity and complexity, and they’re one of the things we’re lucky enough to be able to take for granted in the 21st century.

It starts with an LED. You know, a light-emitting diode, just like the indicator lights that adorn everything from your dashboard to your blender. The difference is, of course, that instead of putting out visible light, it puts out infrared light. Infrared light is just light that’s slightly out of the range we can see. Most people confuse infrared light with heat; they’re different things but related in a way that I’ll probably get into in some other tutorial. But, suffice it to say, you can’t warm your hands on an infrared remote. So at the heart of it, a remote isn’t much more than a flashlight. It’s a flashlight that puts out light you can’t see, but really it’s just a flashlight.

The miracle of infrared communication is really in the way that infrared LED flashes. Flashing light codes are some of the oldest forms of long-distance communication. People in North America used smoke signals to get messages from place to place, and ships at sea communicated using Morse code sent over flashing lights at night. When your remote communicates with your TV, DVR, or whatever, it’s just using a flashing light code. Most devices use different sets of flashes, so that you don’t accidentally eject your DVD when trying to turn up the volume (that is, if you still use DVD’s.) A universal remote understands the flashing languages of thousands of different devices and can use them as needed.

The flashing light sequence is generated by the remote, using an LED at the front. Many remotes put a dark red mask in front of the LED but that just makes the remote look better. The dark red color lets infrared light pass easily but blocks a lot of visible light, so you can’t see the little infrared LED. The flashes are fast, and to normal humans it’s pretty hard to tell one from another. If you’re curious, aim your smartphone’s camera at the front of your remote and push a few buttons. Smartphone cameras usually pick up infrared better than your eyes will, so you’ll see the flashes. You probably won’t be able to tell one set of flashes from another, though.

In your device, probably also hidden by a dark red plastic mask, is the infrared receiver. It’s always sitting there interpreting what’s going on in the room around it, even when the device is off. (Think about it, the device needs to interpret the code for “turn me on” when it’s off, right? So it’s always watching… and now you’re creeped out. Sorry about that.)

Here’s where you need to think for a minute. You’ve probably noticed that you don’t have to point your remote very carefully, but you do have to point it in the general direction of your device. Imagine if you will that your remote was a flashlight in a dark room. You’d still see the light even if it wasn’t pointed right at you, but it wouldn’t be as strong. If it was pointed too far away from you, you wouldn’t get much light from it at all. That’s the way it works for infrared remotes, too. People imagine the beam from a remote like a laser, but it’s more like a flashlight that gets wider and dimmer as it gets further away.

From the point of view of your device, the room isn’t completely dark. There are other sources of infrared light, including light bulbs and the sun, so a remote signal has to be strong enough to be seen even with that other infrared light bouncing around. That’s why the remote won’t work more than a few feet away.

Now that you know how an infrared remote works, and assuming you’re still not creeped out by the fact that the IR receiver is always looking out at you, you can truly enjoy every single one of those remotes in the bucket, even the really really old ones. Then, you know, maybe you’ll be able to responsibly recycle that TV remote from 1983. You know you don’t really need it anymore, right?