Home automation with RC wall plugs and Raspberry Pi

[Jake] took some cheap hardware and figured out a way to use it as a huge home automation network. He’s chose a Raspberry Pi board to connect the radio controlled power outlets to his network. He wrote about his project in two parts, the first is hacking the RC outlet controller and the second is using the Raspberry Pi to manipulate it.

These RC outlets are a pass-through for appliances that connect to mains (lamps, consumer electronics, christmas trees, etc). Often the protocol used by the cheap-as-dirt remote is difficult to work with, but [Jake] really hit it out of the part on this one. In addition to simulating button presses for up to fifteen devices on the remote, he replaced the DIP switch package. This lets him change the encoding, essentially allowing the one device to control up to 32 sets of outlets. Theoretically this lets him command 480 devices from the Raspberry Pi. Since that board is a web server it’s just a matter of coding an interface.

Some of the inspiration for this hack came from the whistle-controlled appliance hack.

Kilonode: how to test a huge Xbee mesh network

So let’s say that you’re a developer on the Xbee team. You need to test the extremes of what the RF radio modules can do when in a large network. But in addition to numerous nodes, you also need to test the effects of distance on the radios. Since it’s not reasonable to distribute hundreds of the devices (each with their own power source) throughout town, you build a test setup like the 1 kilonode Xbee rig which the project manager, [Jared Hofhiens] is showing off.

He’s holding one blade from the rack-mounted system. Each of those squares is an Xbee module, there’s 32 etched onto the board. On the edge furthest from him there are a set of connectors which mate with the rack connectors, hooking the blade up to a set of terminal servers. These servers allow developers to ssh into individual modules. On the near side of the blade there’s a set of attenuation adjustment circuits. They allow adjustments of 0-40 dB of attenuation in 10 dB increments to adjust how strong the RF signals are, simulating distance between modules.

Thirty-two of these cards are mounted in the three racks seen above to make up the 1024 module node. We really appreciate this look behind the scenes and think you’ll enjoy the video tour after the break. If it leaves you wanting more check out how one company builds cloud storage. [Read more...]

LayerOne badges stop bullets; drive away

We love badges. And we’ve really got to thank [Charliex] for taking the time to write a huge post about this year’s LayerOne badges, especially since they’ve got their backs up against the deadline for pulling everything together in time.

Here it is, the stock badge on the left, with an add-on shield on the right. Now the original intent was to make this badge the chassis of an RC car. [Charliex] chewed through his development time trying to source toy cars that could be gutted for parts that would mount easily on the badge. This looked promising at first, but turned out to be folly. Instead what we have here is an Arduino compatible board with an RF transmitter which can be cut off and used separately if you wish. Attendees will be able to use the badge to take control of the toy cars (cases of them have been shipped to the conference), with the option to use the USB functionality to facilitate automation.

So what about stopping bullets? There is a bug in the module [Charliex] used to export the board design from Eagle. They came back from the fab house as 0.125″ substrate. That’s pretty beefy!

The conference is this weekend… better get on that!

The pi pad

In the world of electronics we have impedance; the combination of all forces which oppose the flow of electric current. Often times we have circuits with different impedances, 50 ohms for RF, or 75 for cable TV. It’s pretty important to use the right coax in these circuits, else you’ll be wondering why your RG-58 antenna feed line doesn’t give you anything good to watch.

It’s pretty important to match impedances when connecting different circuits. Apart from the obvious flaws such as a 50 ohm load blowing up a 300 ohm amplifier, there are subtler things such as signal reflection and destructive interference which might just be enough to break whatever it is your playing with. RF mosfets are not cheap! But how could we match impedances? Well we could always use a transformer, but those are rather expensive and bulky. What if we only have a box of resistors to play with? [Read more...]

Whistle controls for you home electronics

You know how to whistle don’t you? You just put your lips together and blow. But do you know how to make the electronics around you react to your whistled commands? Well [Befi] figured out a system that allows him to assign a whistled command to various home electronics.

He’s using a set of RF remote control outlets to switch power to various devices like a desk lap, or a turn table. The board you see in the image above is the remote control that came with the system, but that chip is an ATmega8 which he added to give round-about USB connectivity using a serial-to-USB converter. The technique is simple enough that we’d bet you can get this to work with an ATtiny2313 and the V-USB project but that’s another story.

The additional piece is the use of embedded Linux to detect and process whistled commands. In the video after the break [Befi] explains that he’s using a Dockstar along with a microphone to capture audio input. It uses a Fast Fourier transform algorithm to process the clip and pushes commands to the remote control after processing is complete. [Read more...]

Wardriving for Zigbee

Wardriving started out as a search for unprotected WiFi access points before hot spots were prevalent. And so this ZigBee protocol wardriving hardware which [Travis Goodspeed] put together really gives us a sense of nostalgia for that time. Don’t get us wrong, we love our pervasive WiFi access and don’t wish to go back to simpler times. But if the radio signals your looking for are scarce, locating them provides a challenge.

Regular readers will recognize that [Travis] is interested in all things RF. One of his projects included sniffing wireless keyboard packets out of thin air and displaying them on the screen of his Nokia N900. This is right along those lines but he’s upgraded to an N9 phone for the display hardware. He switched up the RF hardware, using a TelosB (a board he’s already familiar with) to get on the 802.15.4 ZigBee spectrum. This dev board has an expansion port which let him use an RN42 module for wireless communications with the phone. This means the sniffing hardware can be hidden away in a backpack or jacket. After all, nobody will question someone walking around staring at a smart phone.

Designing a Smarter RF transceiver

Two  months ago we featured a transceiver based on the Microchip MRF49XA, and a lot of feedback was sent to [hpux735] requesting that some brains be added onto the system. [hpux735] decided that if he was going to do it, might as well go the distance and make a make a native USB transceiver.

The prototype model is designed for use with the Atmel AT90USBKey, and uses the LUFA USB framework. The protocol and packet format was revised, and a Hamming Code implementation was built using look-up tables to give error control. Finally once the prototype was ready to go [hpux735] created some awesome little PCB’s that contain the AVR, radio, antenna hookups, and blinky lights (no project is complete without blinky lights) are all ready to go when you are.

This project has come quite a long way, covers 3 blog pages, uses a fair bit of ribbon cable, but you just got to love when a plan comes together.