IR Extenders

IR Extenders

Ever since the first remote controls for televisions came out in the 1950s, mankind has been fascinated with the idea of controlling their television, stereo, VCR, DVD player, and everything else they could without having to get out of their comfortable chairs. Today, we have remote controlled fans, microwaves, lights for our homes, and as soon as somebody figures out how to do it, I'm sure we'll have a remote controlled device to
walk the dog.

I remember those early remotes, my grandparents had one. It had four buttons on it, allowing you to change the channel up or down, mute the sound, or adjust the volume and turn the television on or off. But, that early
controller didn't work the way they do today; it worked by ultrasound (high-frequency sounds). When you pushed one of the buttons, it "clicked," striking a metal bar inside the unit, which in turn produced the sound; each of
the buttons hit a different bar, producing a different sound.

While that wireless controller was a technological breakthrough in its day, it was nothing compared to modern infrared controllers, which can perform a multitude of tasks, including tasks that aren't even accessible from the devices main control panel.

How Infrared (IR) is Used in Controllers

Infrared, is electromagnetic energy in a frequency range directly below the visible light spectrum. It most often registers as thermal radiation, or in other words room-temperature heat. If we look at the electromagnetic light spectrum, we find infrared (highlighted in yellow on this diagram).

Light Spectrum


Infrared is light, but it's not visible to the human eye. However, we can develop instrumentation that is capable of "seeing" this light. Infrared photography, whether film or electronic, is able to capture images in infrared.

As with other light, infrared can change somewhat in frequency, and it can also have data imposed upon it through a number of means.
These means include:

  • Shifting the frequency (frequency modulation) of the light slightly to carry analog signals or to indicate digital ones and zeroes
  • Interrupting the light (pulse modulation), forming digital ones and zeros, somewhat like sending Morse code
  • Shifting the strength or amplitude of the light (amplitude modulation) to carry analog signals or to indicate digital ones and zeros

Which of these methods are used depends upon the manufacturer, as there are no universal standards for infrared controllers. Phillips created one, which some other companies have used, but it is not widely accepted as a standard. Japanese companies have some similarity of design, with their controllers sending a manufacturer's identifying code before sending the signal.

IR Control Circuits

Today, almost all remote controllers are digital, having a simple internal microprocessor, which converts button pushes into 4-bit digital codes. These codes are modulated and transmitted by an infrared diode. An infrared phototransistor in the device being controlled (usually hidden behind a window in the control panel) receives this signal. Another microprocessor decodes this signal, which it then passes it on to the device being controlled.

You must realize that the microprocessors used for the coding and decoding these signals are about as complicated as what you'd find in an average digital watch. They are amongst the simplest microprocessors available today.

Universal controllers are only controllers that have been programmed to replicate the various programming styles that different manufacturers have used. When you buy a universal controller, you have to "program it", letting it know the devices it will be controlling. This essentially means inputting a four digit code, and assigning that to one of the device selection buttons. From then on, at least until your batteries die, every time you press the button to select that device (tv, DVD, stereo) the universal controller will replicate the way that the manufacturer's controllers

Two important little notes I need to mention about universal controllers. First of all, when the battery dies or is removed, so is the code you put in. Don't lose your instructions, or you'll be buying a new universal remote. The second thing is that they don't replicate your devices controller perfectly. So, you may find that some commands don't work properly.

Besides the problem of not having a standard that everyone agrees on, meaning that you and your friends need a collection of controllers to manage your entertainment center, the other big problem with IR remotes is that because they are operating by transmitting light, they are limited to line-of-site operation.

Time for an IR Extender

This is where IR Extenders come in to help us out. Let's say that you want to be able to control the entertainment center in your living room from your master bedroom. That way, when the kids are being too noisy at night, you can turn off the TV (okay, maybe you've got some other reason to control it).

An IR Extender will allow you to remotely control your TV, or whatever other remote control device you want, like your stereo system, from another room. 
The IR Extender basically consists of two parts:

      •   The receiver - Which picks up the signal from your remote control and sends it
to the transmitter.

      •   The transmitter - Which sends the signal it received on to the IR sensor (phototransistor) in
the device you want to control.

In a sense, an IR Extender is a repeater. Whatever information it receives, it then sends out again. That way, it really doesn't have to understand which system or protocol your device is using. All it has to do is receive the signal and send it back out again.

For an IR Extender to work, the transmitter needs to be located within line-of-site of the device that you are trying to control. The receiver needs to be located within line-of-site of the location where you want to be able to control the device from. For example, you could have your receiver in the kitchen, to control the entertainment center in the living room. This would give you the capability to mute the sound or pause the movie, when you receive a phone call.

IR Extender Systems come in two flavors:

      •   Wired - Where you run a hidden wire from the receiver to the transmitter. Although more work to install, the nice thing is that they are unobtrusive, almost invisible and not a bother.

      •   Wireless - These units have a radio transmitter, which receives the IR signal from your remote control and converts it to radio waves, which are then transmitted to the radio receiver. The radio signal is then converted back to an IR signal and broadcast to the device you want to control. These units are much simpler to install, but are more obvious.


Rich Murphy