Most of our electronic devices in our home such as DVD player, TV, Surround Sound Receiver, are controlled by Infrared (IR). Our regular remote controllers are designed for issuing these IR commands. In order to efficiently use an IR controlled device in our home automation system, there are a few things we need to consider.
Turning it on
Standing in front of our TV, we are in control. If the TV is off, we press that big red button which says POWER, and the TV turns on. Once we decide to turn the TV off, we do exactly the same. We press the big red button which says POWER, and the TV turns off. Simple. Even a toddler can do it. But how about our home automation system?
Definitely Maybe
What is obvious for us, to see whether the TV is on or not, it is a challenge for the home automation system, which has no eyes to see. Using the same button, POWER, is another challenge. Since the POWER button works like a toggle, alternating between on and off, it is quite difficult for the system to exactly determine, what is going to happen, when it sends the POWER command to the TV. If we instruct the system to turn the TV on, while the TV is on, the POWER command will turn it off. So exactly the opposite will happen, not what we asked the system to do.
The INPUT button
Let’s watch a DVD instead of our regular TV channels! Our DVD is conneted to the TV via INPUT2. Simple. We pickup the TV remote, and press the INPUT button. If we can not see the DVD player’s screen at once, we keep pushing the INPUT button, until will finally get to the DVD. Once we are done, we switch back to our regular program, by pressing the same INPUT button, untill the TV signal shows up. That’s another easy task for us, but another difficult task for the automation system.
Working Around
There are many ways to work around these problems, however these methods are still exactly what they are called, they are only a work around. Let’s see an example:
Discrete Infrared controls
Instead of having only POWER and INPUT commands, we can use (if we are lucky to find them) the so called discrete commands. Power ON and Power OFF instead of POWER, and INPUT2, INPUT-TV commands instead of INPUT. This should be good enough!
But let’s see what happens, if we instruct our control system, to use these commands.
The TV is On, and we instruct the control system, to turn the TV on. Since we have a discrete ON command now, that should take care of that. And yes, the TV does not turn off this time, but something else happens. The TV screen blinks for a few second and we loose a few seconds of our favorite TV show.
Let’s try now, the INPUT-TV command. While the we are watching our regular TV channel, let’s issue the INPUT-TV command. Nothing should happen, since we are watching TV already. Once we pushed the INPUT-TV button, the TV screen freezes for a second or two, and switches to TV input, just in case.
If we can live with the work arounds above, our automation system will do what we instruct it to do, even if there will be a few artifacts, during the process.
We deserve better
If we are planning to have a home automation system, we should choose our TV, DVD and other equipment, accordingly. It is most of the time, not even a money issue. Many of the TV, DVD, Receiver manufacturers make the custom installation friendly version of the same products. These custom friendly units are equipped with a 2-way communication device, which allows the automation system to check their current status, and then issue the desired commands accordingly.
The most commonly used 2-way communication method is called RS-232, or serial protocol. It is very easy to recognize those devices which can be controlled via RS-232. They have a 9 pin connector with the label : RS-232.
Load me up
Our home automation system is equipped with serveral RS-232 ports, anticipating this commonly used method, to be the major way controlling our electronic devices.
Connecting our TV via the RS-232 port to the automation system, there is no more maybe. Before the systems would issue the ON command, it will first check the status of the TV, via the RS-232 link. And if the TV sends back the response, that is already On, nothing else need to be done. Clase closed.
