28-03-2012, 04:49 PM
How Remote Controls Work
[attachment=19143]
The world's first remote controls were radio-frequency devices that
directed German naval vessels to crash into Allied boats during
WWI. In WWII, remote controls detonated bombs for the first time.
The end of the great wars left scientists with a brilliant technology
and nowhere to apply it. Sixty years later, some of us spend an hour
looking for the remote before we remember there are buttons on the
TV.
In this article, we'll examine the infrared technology used in most
home theaters, look at the difference between IR and RF remotes,
find out the difference between a "universal" and a "learning" remote
and check out some of the other high-tech features you can find on
remotes today, like PC connectivity, RF extenders and macro
commands.
Infrared Remote Controls: Inside
The dominant remote-control technology in home-theater applications is infrared (IR). Infrared light is
also known as plain-old "heat." The basic premise at work in an IR remote control is the use of light to
carry signals between a remote control and the device it's directing. Infrared light is in the invisible
portion of the electromagnetic spectrum.
Infrared Remote Controls: The Process
Pushing a button on a remote control sets in motion a series of events that causes the controlled
device to carry out a command. The process works something like this:
1. You push the "volume up" button on your remote control, causing it to touch the contact
beneath it and complete the "volume up" circuit on the circuit board. The integrated circuit
detects this.
2. The integrated circuit sends the binary "volume up" command to the LED at the front of the
remote.
3. The LED sends out a series of light pulses that corresponds to the binary "volume up"
command.
Radio Remote Controls
Radio-frequency (RF) remote controls are very common. Garagedoor
openers, car-alarm fobs and radio-controlled toys have always
used radio remotes, and the technology is starting to show up in
other applications, too. They're still pretty rare in home-theater
devices (with the exception of RF extenders, which we'll discuss on
the next page), but you will find RF remotes controlling certain
satellite-TV receivers and high-end stereo systems. You'll also find
Bluetooth-based remotes that control laptops and smartphones.
(See How Bluetooth Works to learn about this radio technology.)
Instead of sending out light signals, an RF remote transmits radio
waves that correspond to the binary command for the button you're
pushing. A radio receiver on the controlled device receives the
signal and decodes it. The problem with RF remotes is the sheer
number of radio signals flying through the air at any given time. Cell
phones, walkie-talkies, WiFi setups and cordless phones are all
transmitting radio signals at varying frequencies. RF remotes
address the interference issue by transmitting at specific radio
frequencies and by embedding digital address codes in the radio
signal. This lets the radio receiver on the intended device know
when to respond to the signal and when to ignore it. To learn more
about the technology of radio-frequency remotes, check out How
Remote Entry Works.
[attachment=19143]
The world's first remote controls were radio-frequency devices that
directed German naval vessels to crash into Allied boats during
WWI. In WWII, remote controls detonated bombs for the first time.
The end of the great wars left scientists with a brilliant technology
and nowhere to apply it. Sixty years later, some of us spend an hour
looking for the remote before we remember there are buttons on the
TV.
In this article, we'll examine the infrared technology used in most
home theaters, look at the difference between IR and RF remotes,
find out the difference between a "universal" and a "learning" remote
and check out some of the other high-tech features you can find on
remotes today, like PC connectivity, RF extenders and macro
commands.
Infrared Remote Controls: Inside
The dominant remote-control technology in home-theater applications is infrared (IR). Infrared light is
also known as plain-old "heat." The basic premise at work in an IR remote control is the use of light to
carry signals between a remote control and the device it's directing. Infrared light is in the invisible
portion of the electromagnetic spectrum.
Infrared Remote Controls: The Process
Pushing a button on a remote control sets in motion a series of events that causes the controlled
device to carry out a command. The process works something like this:
1. You push the "volume up" button on your remote control, causing it to touch the contact
beneath it and complete the "volume up" circuit on the circuit board. The integrated circuit
detects this.
2. The integrated circuit sends the binary "volume up" command to the LED at the front of the
remote.
3. The LED sends out a series of light pulses that corresponds to the binary "volume up"
command.
Radio Remote Controls
Radio-frequency (RF) remote controls are very common. Garagedoor
openers, car-alarm fobs and radio-controlled toys have always
used radio remotes, and the technology is starting to show up in
other applications, too. They're still pretty rare in home-theater
devices (with the exception of RF extenders, which we'll discuss on
the next page), but you will find RF remotes controlling certain
satellite-TV receivers and high-end stereo systems. You'll also find
Bluetooth-based remotes that control laptops and smartphones.
(See How Bluetooth Works to learn about this radio technology.)
Instead of sending out light signals, an RF remote transmits radio
waves that correspond to the binary command for the button you're
pushing. A radio receiver on the controlled device receives the
signal and decodes it. The problem with RF remotes is the sheer
number of radio signals flying through the air at any given time. Cell
phones, walkie-talkies, WiFi setups and cordless phones are all
transmitting radio signals at varying frequencies. RF remotes
address the interference issue by transmitting at specific radio
frequencies and by embedding digital address codes in the radio
signal. This lets the radio receiver on the intended device know
when to respond to the signal and when to ignore it. To learn more
about the technology of radio-frequency remotes, check out How
Remote Entry Works.