Twitip

Last year one of the interesting posts in TwiTip that really caught my attention was the post about how to turn a bedroom light on and off with Twitter.

In the comment, I hinted about how that hack works — after peeking at the source code. For most people, it appears like magic but really it is quite simple if you understand how different parts interact.

Once you are aware about how a typical system like this works, hopefully you can come up with more ideas to make use of the technology.

What Do You Need?

What appears to be magic actually is a set of tools and electronic devices working together. Each of them is able to communicate with the device next or before it.

There are a few components that work together in the light switch scenario:

1. A computer system with controlling software. Obviously the computer has to be on for it to accept messages and to send them to the right devices. Smart home devices also have programmable controller and remote so signals could also be sent from this remote instead of a computer.
2. A hardware controller. You need an electronic circuit that is able to receive signals from your computer (either via serial or USB port) and respond to it. It can be as simple as an on-off switch. If the device includes support for dimming lights, you will be able to extend the feature to dim instead of just turning on and off. As you see, the controller plays a critical role here.
3. The controlled object. In this case, it is a light. There is nothing special about the object. Just that the signal from the controlling device — most likely computer — instruct the controller to do something that in turn do whatever it is programmed to do to the object.
4. Communication mechanism. The last part of the system is a communication mechanism that lets you send signal to the computer system.

There are many ways to send instruction signals to your computer. Some email clients are able to filter subject line or content body and then run custom command. That means you can control and execute the controlling software wherever you have an email client.

An alternative would be posting a Twitter message (via cellphone or any Twitter client). Using Kwiry and Jott, you may even use your voice to post to Twitter. Ping.fm lets you use cellphone, instant messaging services, and others to send your message to Twitter.

Of course, you are not limited to Twitter. As long as you can fetch the data and process it later with your computer, you can use it as a communication mechanism.

I bet you can come up a few other options right now, can’t you?

How to Control Bedroom Light with Twitter

As a simple example, based on the model above, allow me to explain how to control the light with your cellphone and Twitter.

First of all, the setup requires a controller like Insteon PowerLinc Controller. The controller is able to connect to the computer via a USB interface, which in turn sends signal to a light dimmer. Setup is necessary to identify the device you want to control.

That’s for the hardware and controller part. The next thing is to find a way to setup the software so it sends signal to the controller. iLink Insteon scene management software is available under Linux with both graphical and command line interface.

With the command line version, you can type in command and instruct the controller to send the appropriate signal to the dimmer. Once that works, you need to automate the command.

This is when Twitter plays a role. With the published RSS feed, a simple script can be used to poll the RSS on a regular basis — such as every second. Based on the content of the tweet, the script execute the appropriate command to turn the light on and off.

Of course, you may want to setup a separate Twitter account just for this to avoid confusing your followers with your home automation command.

If you need real-time response, Twitter may not be suitable for this application because that means you have to rely on Twitter and the speed of which it updates the RSS feed. However, controlling devices via Twitter sounds just cool.

Note: Yes, with such setup, you can also send an instruction to turn the light on and off using your instant messaging client if you set that up first, such as using ping.fm.

Possible Applications

Imagination is the limit when it comes to applying this setup to other things. Switching the light on and off may just be the easiest application.

Here are some other ideas to start with:

• Turn another computer on and off. Shutdown can be done with the shutdown command, available in both Windows and Linux. I’m sure there is a similar function with Mac-based computer as basically it is UNIX-based. Turning on the machine is a bit tricky though. But one possible idea would be to enable wake up on LAN feature, both in the motherboard and the BIOS and then trigger the data packet through another computer.
• Brew coffee. Isn’t it great if you are able to turn the coffee machine on so it starts brewing coffee even before you get off the bed? A simple on and off electric circuit can help you. It works pretty much like the light switch scenario. Now even if your coffee maker doesn’t come with a programmable timer, you can have a cup of your favorite coffee ready before you walk out of your bedroom. Of course, the coffee maker has to be loaded with coffee and water and setup in a way that it automatically runs when it is powered.
• Play a song / music / recording. Wouldn’t it be nice if you could come home with your favorite music welcoming you? How about recording your voice and then play it back when someone else in the room? Many media players allow you to run them via command line and specify the name of the music or media files for playback.
• Run software program. It is possible to instruct your computer to execute certain software program, such as performing data backup to another partition or even to another host.
• Adjust room temperature. This can be as simple as turning the air conditioner on or off. More advanced options can be made available if the software supports them.

Basically what you can do depends on the controlling software and hardware.

Home automation is quite a popular topic recently. Thanks to the Internet and various communication protocols, now controlling various devices become easier, although some of the solutions are less elegant than others.

This post may not be particularly useful for mission critical task, but I think you’ll agree it makes a fun project for the weekend.

Leave your ideas and thoughts about it below.

Hendry Lee helps bloggers overcome strategic and technological challenges in starting and growing their blogs.

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Follow Hendry on Twitter (@hendrylee).