IR - Extending an IR receiver
- 1 Applications for extending an IR receiver
- 2 Overview of IR recievers
- 3 Wiring
- 4 Types of IR detectors
- 5 Extending an IR dongle
- 5.1 Preparing the plug end
- 5.2 Preparing the receiver end
- 6 References
- 7 See Also
Applications for extending an IR receiver
Moving a MythTV (or any media center machine for that matter) to a location other than that of the display can often be the most affordable solution to the stubborn problem of noise. Space constraints or aestetics may prevent a machine from residing near the display. Power-users often centralize their equipment to a machine room in the basement such as this fellow has.
Ultimately, if the machine that needs to be controlled is not within line-of-sight (LOS) of the remote control or outside of it's nominal range, an IR receiver mounted in the viewing room can be wired to the remotely installed frontend. A classic example is the common practice of moving the machine to a cupboard or room [under the stairs] because space isn't available in a small apartment.
Another popular practice with the advent of the wall mounted flat-panel display is to hide all of the existing home theatre equipment in a rack or enclosure flush to a wall or hiding them behind a panel or in a nearby closet, thus creating a streamlined or minimalist decor.
In this scenario each piece of equipment would also need to have it's respective IR signal forwarded or "repeated". An IR control system would be used to collect, concentrate and then deliver the signals from any remote control to the proper piece of equipment (eg. HT receiver, sat/cable box, DVD).
Regardless of the control system used to forward the IR signals, the room where a user will control the equipment must have some form of IR receiver which should be mounted in a location where the user's remote control will maintain maximum LOS. In most cases the IR receiver cable supplied with many tuner cards (often called a "dongle") isn't long enough to reach the remotely located machine.
These receivers use a small IR diode encased in plastic leading to a short three-conductor cord which terminates in a connector, typically a 2.5mm stereo phone plug or DB-9 serial port connector.
Additionally, the methods used in this article extend to the use of home-built IR receivers, ready-built do-it-yourself (DIY), retail and commercial offerings. Furthermore, a remote computer running lirc can be used as a powerful IR control system as described by Mike Dean on mythtv-users. Many of the prebuilt and retail solutions also include an IR blaster making them a transceiver. Lirc can be configured to use an emitter, blaster or direct wiring to control external components such as set top boxes for cable or sat, your TV and even your A/V receiver. With some scripting finesse, a complete automation system can be designed around Lirc.
Overview of IR recievers
An IR receiver at a minimum consists of an IR detecting diode such as the Vishay TSOP 17xx series (datasheet, PDF) which detects the IR energy pulses and converts them to an electrical signal. The diode requires voltage to operate, a signal line to transmit the signal, and a ground. A diode is often used to provide rudimentary over-voltage protection and a voltage regulator can be used to provide more exacting regulation. Here is a schematic from Trimbitas Sorin's excellent blogpost which details the typical application of an IR detecting diode.
The detection device usually requires +5V but can often be packaged with a voltage regulator expecting higher voltages. Many commercial receivers require +12V and have additional capabilities such as talkback LED's to indicate when a button is being pressed. Always refer to the supplied documentation for proper usage.
An IR receiver also requires decoding circuitry which is generally found on the tuner card or device. In the case of a USB connected device, the decoding circuitry is located alongside the detector
Nearly any type of low voltage cable can be used to carry IR signals. VCC is generally 5-12V and the signal is usually ~3-4V. With that in mind, it becomes obvious that a 4-conductor, 12-gauge speaker cable is not an ideal choice as any considerable length will introduce excessive resistance to the circuit. Common cable types used to carry IR signals are:
- Category 5 (Unshielded Twisted Pair, solid 26ga, 8 conductor in 4 pairs)
- Security cable (Unshielded, solid 22ga, 4 conductor)
- Audio cable (Shielded Twisted Pair, 22ga, 2 conductor)
- Coaxial cable using [#Over coaxial cable|baluns or transceivers (RG/59 or RG/6, typical)
Types of IR detectors
Dongles bundled with tuner cards
The following is a listing of IR capable tuner cards. Most will ship with a remote and the IR dongle but some OEM cards may ship with the jack and associated receiver circuitry.
Readybuilt -- Retail
For the less adventurous, prebuilt receivers can be purchased. Some of the original vendors have since closed doors but are included here for completeness and because some sites are still up and contain useful information.
- IR Blaster.info has separate serial IR receivers and blasters for sale
- IguanaWorks makes a very tidy little kit which has an exceptionally high-powered transmitter that you can buy from them unassembled or assembled (slightly more) for around $30USD.
- USB-UIRT makes a USB infrared transceiver which works well with LIRC.
- CommandIR Mini combines multiple IR blasters with a built-in universal remote receiver. It's a Linux-only device so a bit pricier but you get a guarantee it will work with devices like set-top boxes, Linux tech support, and setup that doesn't require multiple LIRC instances.
DIY -- Homebrew
- Lirc's own page for do-it-yourselfers
- Trimbitas Soren's excellent blog write-up with diagrams and detailed photographs with tools]
- The Manoweb Site also has excellent documentation and photgraphs of how to build your own serial port receiever (the proprietor originally sold them over the internet but indicates on the site that as of 2007 Jul, pre-built receivers will no longer be shipped)
Extending an IR dongle
IR dongles are, in effect, the tail end of the full receiver circuit which resides on the tuner card or module (with the notable exception of USB connected IR receivers). The rest of the circuitry resides on the tuner card or device and all that is needed to make the cable longer is some length of suitable cable, some tools and a way to connect it all back together again.
Preparing the plug end
Cut and prepare the receiver cable
Identify the cable conductors
Prepare and solder Category 5 to jack end of cable
Punching down to the telephone connecting block
- 66block 01.jpg
1. Identify the pairs or conductors needed
- 66block 02.jpg
2. Punch down green pairs
- 66block 03.jpg
3. Splice and crimp the white/brown conductor
- Hauppauge 04.jpg
4. Connect stereo plug to capture card
Preparing the receiver end
Connecting receiver cable to RJ-45 modular connector
2. Cut conductors to length for connector insertion
Connecting Category 5 cable to RJ45 keystone
- Wallplate quadkey.jpg
3. Attaching to wall-plate
4. Installing receiver cable
General Overview of IR Transmission in Free Space, Vishay Corp.
Disturbance Sources for IR Receiver Modules, Vishay Corp.