Skip to main content

Understanding IR Remote Controls

By
When hearing the word 'Remote Control', the first thing that comes to most people’s mind would be the TV remote control. They have become so common that other devices - CD/DVD players, Fans, Air-conditioners, Refrigerators, Washing machines etc. - are also getting the same sort of remote controls. These days it's easy to find that almost all consumer electronic devices have a remote control.
Almost all of these are IR remote controls.

What is IR?
IR, or Infrared, is an electromagnetic radiation that has a wavelength between 0.7 and 300 micrometers (frequency range between 1 THz and 430 THz).
The Electromagnetic Spectrum

There are several advantages in choosing IR for remote controls, such as:
  • Low power requirements
  • Low circuitry costs
  • Simple circuitry
  • Portability
  • Few international regulatory constraints
  • High noise immunity 
However, there are a few disadvantages like requiring line of sight, blocked by common materials, short range and light and weather sensitive. Most of these aren't much of a problem with basic remote controls. Interference from sunlight and other IR sources could pose a problem to them. This problem is normally avoided by adding an IR filter that is only sensitive to the specific frequency range of IR remotes (the dark coloured piece of plastic on the remote and on the receiver is this filter).

Another technique is to modulate the IR signal to a frequency between 30 KHz and 60 KHz. Since IR radiation from the sun or other IR sources isn’t modulated, it's easy to filter out the noise caused by them and get only the modulated signal.

Let’s talk about some of the common IR encoding methods used in remote controls in the next post.

References
http://en.wikipedia.org/wiki/Infrared
http://en.wikipedia.org/wiki/Electromagnetic_spectrum
http://trace.wisc.edu/docs/ir_intro/ir_intro.htm
    Labels:

    Comments

    1. Sandeep EllawalaJanuary 10, 2011 at 9:57 AM

      I was just wondering, now if we modulate Infrared signals into 30KHz-60KHz frequency range, they fall down the spectrum of frequencies and basically propagate as radio signals of low frequency. What kind of changes can we expect in this case compared to IR. For an example, propagation distance would have a direct impact I suppose.

      ReplyDelete
    2. Thimira AmaratungaJanuary 10, 2011 at 11:06 AM

      My knowledge of theories associated with signal propagation is very low (for now...), but I think the higher frequency determines the propagating distance. So, i think that the higher frequency modulated to a lower is equivalent to the same lower frequency modulated to the higher, which would make the propagation distance the same in both cases. I might be wrong about it. We'll need an opinion of an actual expert in signal physics...

      ReplyDelete
    3. Sandeep EllawalaJanuary 10, 2011 at 12:47 PM

      Modulating a signal from one frequency to another would not destroy the signal pattern itself. This is what happens exactly in the standard Analog telephone system. Near exact reproduction of a signal of high frequency can be achieved with a lower frequency signal. I have to agree on that with you. But 30KHz - 60KHz is less prone to effects from sunlight and such I think because they belong to ground wave range. Let's see if someone with better expertise can come up with an answer.

      ReplyDelete

    Post a Comment

    Popular posts from this blog

    Selecting the Correct Gauge Wires for your RC Models

    By
    When we are building RC models (aircrafts, multicopters etc.), something we typically overlook is what type of wires to use to distribute power in them. Usually, we try to reduce the weight of the model, so we tend to go with smaller wires. But, we cant expect to put in small circuit-wires and have them handle the amount of power needed. If you look at the wires that comes in the output leads of a Li-Po, or the wires that comes on a standard XT Jack, you'll notice that they're quite huge. Large gauge wires on a Li-Po and XT connectors These need to be huge to handle the amount of amperage that goes through them. So, we should also consider the amperage, and the length of wire needed when selecting the size (gauge) of the wires.
    Post a Comment
    Read more

    What do the prop size numbers mean?

    By
    Have you been trying to shop for propellers - either online or at a hobby shop - and got confused of the numbering used to denote the size of the propellers? You see things like " 10 x 4.5 CW ", or " 8055 CCW ". What do these numbers mean? A 8 x 4.5 CW and CCW Propeller Set It's actually quite simple once you figure it out. The first number denotes the diameter of the prop (length from tip-to-tip). The second number denotes the pitch of the prop. Here, the pitch is denoted as a length, not a angle. Let's see how that works.
    1 comment
    Read more

    Li-Po Batteries Explained - Part 2

    By
    I explained about Li-ion batteries (the predecessor of Li-Po) in my earlier post ( Li-Po Batteries Explained - Part 1 ). Now let's see what these 'Lithium Polymers' are. Lithium-Polymer Batteries - The real ones Li-Po batteries - also known as Li-Poly, Pi-Pol, PLI and PLI - are a type of rechargeable batteries that uses same types of electrodes as the Li-ion batteries. The difference is with the electrolyte it uses. Instead of the liquid solvent used in Li-ions, Li-Po uses a polymer electrolyte. In the original design, which dates back to the 1970's, the electrolyte is a dry, plastic-like, thin film. It doesn't conduct electricity, but allows the exchange of ions between the electrodes. Theoretically, with this design, batteries could be made very thin (less than 1 millimeter) and to a variety of form factors. And because of the electrolyte being dry, the manufacturing process can be simplified and the safety of the battery will be higher because of no risk in
    2 comments
    Read more