The Why and How of Infrared Repeater Systems
Infrared (IR) is a long wavelength light in the band that exists below visibility to the human eye. IR-wavelength light emitting diodes (LEDs) are used in remote controls because the diodes require very little power. They are able to turn on and off quickly enough to create the digitally-coded messages to which remotely-controlled devices respond. Being light invisible to the human eye, an IR pulse is not distracting or annoying when activated.
IR repeater systems are used most commonly with audio/video systems that distribute video and sound throughout multiple rooms or locations in a home or business. They can enable full control over each component in the system from every distributed location, assuming each component in the system works with an IR remote.
The IR "window" or pickup on remotely-controlled components contains a device called a photo diode. These devices are designed to respond to infrared light, recreating the digital code as an electrical pulse, which causes the audio or video component to respond in the desired manner. There are literally hundreds of different code sets for consumer electronics products.
IR repeater systems are so-named because they simply reproduce the IR code generated by an IR remote. The basic system consists of:
- The connecting block that accommodates the power supply and connections
- One or more photo diode units (often referred to as the "repeater" or IR target)
- One or more "emitter" or IR flasher LEDs
Three conductors are required in the hook up wire running from the connecting block: two for DC power and one to carry the signal. The same type of wire used for telephone lines or alarm systems is commonly used in repeater systems, and is generally run in-wall back to the IR connecting block.
The emitter LEDs "flash" the code for the audio/video components to be controlled, as seen by the IR target's photo diode. A target must be installed and wired in every location where control over the A/V system is desired. Targets are usually designed to mount into a standard electrical junction box in a location that offers reasonable exposure to the remote control's IR commands.
When the IR remote is pointed at the target and any button is pressed, the photo diode "sees" the IR emitted by the diode in the remote and creates an electrical pulse equivalent to the IR code. This code is transmitted back to the connecting block, which also provides power for the targets and flashers, and then on to the A/V components requiring control commands.
Flasher diode holders typically include a pressure-sensitive adhesive that attaches the LED directly over the IR window of each home theater receiver, media player, satellite box, etc. When the connecting block receives the pulsed code from any target, it causes all of the emitter diodes to flash the code. Only the A/V component that "recognizes" the code will respond. Universal remotes are often used at each target location along with that monitor or TV's remote. Modern universal remotes will operate most functions on home audio/video equipment.