The wooden frame seen above hosts a parabolic reflector making up one side of a wireless network link. This is a Fab Lab project called FabFi which uses common networking hardware to setup long-distance wireless Ethernet connections. It’s a bit hard to tell in the image above, but the reflector focuses radio waves on the antennae of a router we’re quite familiar with, the Linksys WRT54G. It’s held upside-down in an enclosure meant to protect it from the elements. The node above manages to complete a connection spanning 2.41 miles!

One of the core values of the project is to develop hardware that is easy to build with limited resources, then to make that knowledge freely available. Anyone who has the ability to download and print out the 2D design file can build a reflector for themselves. As we’ve seen in other projects, paper stencils and hand tools can handle this job with no need for a laser-cutter (which was used for the prototype). WRT54G routers are inexpensive and the project uses the open source firmware OpenWRT. They can be run from 12VDC power which means a car battery works when mains power is not an option. The system has been running in Afghanistan for two years and hardware failure is still in the low single-digits.

[Thanks das_coach]

The Linksys router seen about is a WRT54G version 1. It famously runs Linux and was the source of much hacking back in the heyday, leading to popular alternative firmware packages such as DD-WRT and Tomato. But the company went away from a Linux-based firmware starting with version 8 of the hardware. Now they are using a proprietary Real Time Operating System called VxWorks.

[Craig] recently put together a reverse engineering guide for WRT54Gv8 and newer routers. His approach is purely firmware based since he doesn’t actually own a router that runs VxWorks. A bit of poking around in the hex dump lets him identify different parts of the files, leading to an ELF header that really starts to unlock the secrets within. From there he carries out a rather lengthy process of accurately disassembling the code into something that makes sense. The tool of choice used for this is IDA Pro diassembler and debugger. We weren’t previously familiar with it, but having seen what it can do we’re quite impressed.

[Image via Wikimedia Commons]

[Chris Kantarjiev] is an amateur radio enthusiast (call sign K6DBG) and does a lot with the APRS. We think his build, turning a WRT54gl router into an APRS gateway will be very useful for the APRS tracker builds we’ve been covering.

Setting up an Internet Gateway, or igate, on APRS usually requires a ‘real’ computer. [Chris] didn’t like that idea, so he took aprs4r, igate software for embedded devices, and pruned it down to fit on the 4MB of flash and 16MB of RAM in the WRT.

The actual APRS hardware is connected though headers soldered onto the WRT54gl’s board which go to a small PIC-Based TNC. [Chris] argues that the APRS ‘backbone’ is great, but there aren’t enough nodes on the network for full coverage. We thing this would be a great way to put cheap hardware out in the wild to cover those gaps in the APRS network.

Check out the video for a rundown of the modded WRT54g after the break. If you’re interested amateur radio, Field Day is coming up in just 2 weeks. Find a local club and check out what’s possible with amateur radio.

Meet TIPI, the Telepresence Interface by Pendulum Inversion. TIPI is something of a surrogate, giving physical presence to telecommuters by balancing an LCD screen and camera atop its six foot frame. The user has full control of the robot’s movement, with their own camera image shown on the display so that others interacting with the bot will with whom they are conversing.

A pair of 12.5″ wheels connec to DC motors via a gear box with a 37:1 ratio. These specs are necessary to recover from a sudden 20 degree loss of equilibrium, quite impressive for a bot of this stature. An Orangutan SVP board monitors a two-axis accelerometer and a gyroscope for accurate positioning data. This board automatically keeps balance, while taking user commands from a second control, a Beagle Board. The Beagle Board handles the communications, including sending and receiving the video signals, and delivering incoming position control data to the Orangutan. Separating the two systems guards against a screen-shattering fall by making sure the hardware likely to face slow-down or lockup is physically separate from that responsible for balance.

Check out the video clip after the brake to see some balancing goodness. It shouldn’t be hard to build your own version for much less than the $15k price tag enjoyed by some commercial versions.

[Tom Lee] and his colleagues just moved to a new office. The doors are setup like a security checkpoint with electronic strikes and buttons on the inside to allow entry. The button simply completes a low-voltage circuit, activating the strike which made it quite easy to patch into. They build an interface board with a small relay to complete that circuit. As we’ve seen before, Linksys routers have plenty of extra room in the case so there was no problem housing the new circuit in this tiny network device. Now [Nicko] and his friends can use a custom app to input an access code or to verify a device ID from a cell phone and gain entry. The door still has keyed locks in case of a power outage. In fact, the only change made to the system was the addition of two wires to the “door release” button as seen above. See the one-touch device ID authentication in the video after the break.

This hack is similar to the GSM door entry from last year. In this case, the phones are communicating with the door via web interface and not the GSM network.

[Thanks Nicko Margolies]

[Craig] wanted to use Boxee on his TV but his computer was in a different room. He rigged up a rather dubious method of delivering the A/V signal (this is a hack in the most guttural sense). More interesting to us is his solution for a remote control interface. We’re familiar with building USB connected infrared receivers but [Craig] decided to patch one into the serial connection on his Linksys WRT54G router.

Surprisingly there’s a lot of space in the router case to add more electronics. He connected a 7805 voltage regulator to the 12v supply for the router and used it to power an IR receiver module and an ATmega328. Because the serial port of the router needs 3.3v he uses a zener diode and resistor to drop the communications voltage. By loading Tomato as the router firmware the remote control signals can be communicated back to a python script running on the host machine.

We do have a few opinions about possible improvements. The use of an ATmega328 is about 30kB worth of overkill. We know that software-based usb infrared receivers run on under 2 kilobytes of programming space. Also, the IR receiver module used (TSOP1738) is obsolete. In this case, we might recommend the TSOP34138. By changing to this part and using a low-power AVR you should be able to run off of the router’s 3.3v regulated supply. This would get rid of the additional regulator and prevent adding even more heat inside the router chassis.

But hardware selection arguments aside, we love the creativity of this solution. Nice work!

Reader [john] finished up his home power monitor over the holiday weekend. It uses a pair of current transducers clamped onto the mains. These output 0-3V and are read by the Arduino’s ADC. The Arduino averages samples over a 20 second period, calculates power used, and uploads it using an Ethernet Shield. The shield can’t do DNS lookups, so he uses a WRT54G to negotiate with the remote webserver. He admits that the system could be more accurate; it can’t detect small loads like wall warts. He also says that money could be saved by talking serial to the router instead of over ethernet. Here are the current usage charts.

You can find many power monitor projects like this in out Home Hacks category.

[Andrey Mikhalchuk] Has posted some great instructions on how to build an inexpensive router based robot. Starting with a Linksys WRT54GL, he takes us through the process of disassembling and modifying it to directly control servos.  He has put together a custom version of OpenWRT Linux that you can download from his site.  After testing to make sure everything is functional, he goes through a quick and dirty chassis build.  As you can see from the picture above, there are lot of household items thrown in there such as rubber bands and zip ties.  After adding a camera mounted on two servos for x y movement, he fine tunes it and lets it go.

This project looks fairly simple, cheap, and fun.  It may look familiar as it is very similar to our Wifi Robot post from August.

[thanks Matt]

[rocketman] has posted about a new event at Defcon dubbed WarBallooning. They are using a Kismet drone (a modified WRT54G), a webcam, and a few high gain antennas. The balloon will be launched at about 15 stories and will be remotely fed targets chosen directly by the Defcon participants. The the directional antenna will be mounted to the camera so pan and tilt can be controlled. The Kismet CSV files will be available for everyone after the event.

If you are interested in WarDriving or building you own high-gain antennas, we suggest you check out this WiFi biquad dish antenna mounted on a car. If cars are too boring, or you do not have one, you could always go WarSailing or WarFlying. Yes, the permutations are endless.

[photo: JoergHL]