Infra-Red Remote Control
A large part of Home Automation is about taking control of devices regardless of where you happen to be. Sooner or later, it inevitably becomes a requirement to capture, simulate or relay infra-red remote control. This article gives an overview of some of the options.
The biggest drawback with IR remote control as a means of operation is that it usually has to operate without any feedback mechanism. As such, it is impossible for a controller to be certain that a command has been correctly actioned. In planning for automated IR control of devices, it is also important to be aware of that people may intervene and set a device to a new, unknown state. This can be particularly tiresome for devices that do not have discrete commands, but instead toggle commands. For example, often the same button on a remote control is used to turn a television both on and off. If a person turns the device off manually, when a controller believes the device is actually on, the next automatic command sent to turn the device off actually turns it on, and chaos reigns.
There are two strategies to circumvent this issue. First, many devices support additional infra red commands over and above those on the supplied remote control - these may include discrete commands for certain toggle actions. A search on the web, or trial and error, can uncover these. The second strategy is to adopt control by proxy: if only the automatic controller is allowed to control a device directly, then there is a good chance that the device will be in a known state. Thus any instruction to the device is routed indirectly via the automatic controller. Whilst in some situations this can be cumbersome, in others it can be an elegant solution to retaining control of the device.
Relaying Infra-Red Signals
Relaying infra-red signals allows control of equipment which isn't in direct line of sight of the remote control. Typical scenarios include controlling a set top box in the lounge from the bedroom (perhaps to change the channel on a satellite or cable receiver), or situations where equipment is hidden out-of-sight - whether in a cupboard or in perhaps in node zero.
In either case, the solution is to relay the infra red signal using a infra red extender. Three options are available: a wireless extender, a wired extender or coax extender.
Wireless extenders generally perform poorly, and can interfere with wireless LAN networks and video senders. I wouldn't recommend one except as a last resort.
Wired extenders demodulate the IR signal, transmit it over low voltage cabling and then reconstruct the signal at the receiving end. Cheap wired extenders are battery powered, the more upmarket models, such as those made by xantech are mains powered. Considering the simple job that wired extenders perform, I think they are unreasonably expensive - if you are handy with a soldering iron, you can readily build your own for no more than a couple of pounds. Nigel Orr's circuit has been successfully constructed by many.
The last category of extender is the coax extender, such as that manufactured by Triax and retailed by Keene Electronics and others. These use the existing aerial distribution system to transmit the infrared signal back to a receiver unit. They work well, and avoid the need for a dedicated cable run between points, but are costly.
Computer Control - Sending IR signals
Simulating a remote control using a computer is very straight forward, although it requires some simple custom hardware. A good starting point the Linux infra-red remote control project, which although Linux specific, provides links to a wide range of generic Infra-red sources. For Windows users, Dante's Infrared Remote Manager provides both details of the hardware and the software required to take generate infra red commands.
Users of the Comfort security system have options for both sending and receiving infrared commands. Through the addition of a simple IR LED, which is available for a few pence from electronic suppliers such as Farnell. By default, Comfort is capable of sending a number of learned IR commands. This capability can be extended to cover an infinite number of commands using ACE software. Comfort can support multiple IR senders: each IR LED requires a dedicated output zone.
Most of the dedicated Home Automation controllers such as Ocelot and Home Vision are also infra-red capable.
PC Computer Control - Receiving IR signals
Demodulating and decoding IR signals is marginally more complex than originating them.
For standalone PC use, IRMan is excellent value and works well - with one caveat - it has to be programmed to discriminate the commands you want to send, in much the same way as a learning remote. Tedious, but not a show stopper for most applications. The unit uses a serial interface, and, with various Visual Basic custom controls are available, it is a doddle to program against.
As mentioned previously, the Linux infra-red remote control project also provides plenty of detail regarding receiving IR signals.
Universal Remote Controls
Universal remote controls provide an effective way of eliminating remote-control clutter, and if the Home Automation controllers are IR enabled, can also provide an effective interface to the house control systems. For impartial advice on programmable remote controls in general,Remote Central is probably the definitive resource. Amongst UK Home Automators, the Philips Pronto has an almost cult following. This learning remote has a backlit touch screen and is supplied with software which allows the end user to define and layout their own custom pages for the device. Whilst the Pronto does have shortcomings, I don't think there is anything better on the market at the present time.
|
