Open Source Power Line Communication

April 5, 2014 by Eric Evenchick 40 Comments

Since we all have wires running throughout our houses to provide mains power, there’s a number of devices that piggyback on mains lines for communication. For his thesis project, [Haris Andrianakis] developed his own power line communication system.

The basic principle of the system is to inject a signal onto the power lines at a much higher frequency than the 50 or 60 Hz of the AC power itself. Using both active and passive filters, the signal can be separated from the AC power and decoded. This system uses frequency-shift keying to encode data. This part is done by a ST7540 modem that’s designed for power line applications. The modem is controlled over SPI by an ATmega168 microcontroller.

[Haris]’ write up goes into detail about some of the challenges he faced, and how to protect the device from the high voltages present. The final result is a remote display for a weigh scale, which communicates over the power line. Schematics, PCB layout, and software are all available.

The Mobile Phone PixelSWaLL

April 5, 2014 by James Hobson 12 Comments

As much as we hate to admit it, smart phones have become somewhat of a disposable item in today’s society. People upgrade their phones constantly and simply chuck their old ones. Of course, there’s plenty of things you can do with slightly out of date phones… Here’s one we haven’t seen before — a wireless multi-phone display!

It’s called the PixelSWaLL, and according to the author, his software can control up to 240 Android devices! To run this demo with just 9 phones, he’s using an old Apple Macbook running Windows 7 bootcamp, which sends the display info using an old Telmex router. Each phone or tablet runs the Android terminal application using Eclipse ADT which renders OpenGL in real-time. The server application was made with Delphi 7 and uses the DSPack library to read video files in order to send them over UDP via Indy 10. It’s a bit of a mouthful to explain, but the resulting display array is pretty cool!

Time to start collecting phones…

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Bike Pedals In Both Directions, Gets You To Your Destination AND Back

April 5, 2014 by Rich Bremer 48 Comments

[punamenon2] has built an interesting bike that moves forward regardless if it is pedaled forward or backwards! What? Yes, you read that correctly. Pedal forward or backwards and the bike goes forward. This project started off as any old cruiser with a free-wheeling rear hub. To pull off this mod a second free-wheel and sprocket had to be added to the current wheel assembly. One free-wheel and sprocket set is used when pedaling forward, the other set is used when pedaling in reverse. There is also a new chain tensioner that serves to not only keep the chain taut but also allows for the chain to change directions which ultimately allows this novel idea to work.

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Taking Pictures With A DRAM Chip

April 5, 2014 by Eric Evenchick 65 Comments

This picture was taken by using a DRAM chip as an image sensor (translated). A decapped 64k DRAM chip was combined with optics that could focus an image onto the die. By reading data out of the DRAM, the image could be constructed.

DRAM is the type of RAM you find on the RAM cards inserted into your motherboard. It consists of a massive array of capacitors and transistors. Each bit requires one transistor and one capacitor, which is quite efficient. The downside is that the memory needs to be refreshed periodically to prevent the capacitors from discharging.

Exposing the capacitor to light causes it to discharge faster. Once it has discharged past a certain threshold, the bit will flip from one to zero. To take a picture, ones are written to every bit in the DRAM array. By timing how long it takes a bit to flip from one to zero, the amount of light exposure can be determined. Since the DRAM is laid out in an array, each bit can be treated as a pixel to reconstruct the image.

Sure, modern CCDs are better, cheaper, and faster, but this hack is a neat way to totally re-purpose a chip. There’s even Turbo Pascal source if you’d like to recreate the project.

Thanks to [svofski] for the tip.

Web Interface For The FRAM LaunchPad

April 5, 2014 by Nick Conn 10 Comments

webUILaunchpad The Internet of Things is here in full force. The first step when adding to the Internet of Things is obvious, adding a web interface to your project. [Jaspreet] wrote in to tell us about his project that adds a web interface to his MSP430 based project, making it easy to add any project to the internet of things.

Creating a web interface can be a bit overwhelming if you have never done it before. This project makes it easy by using a dedicated computer running Linux to handle all of the web related tasks. The LaunchPad simply interfaces with the computer using USB and Python, and the computer hosts the webpage and updates it in real time using Node.js. The result is a very professional looking interface with an impressively responsive display that can control the on-board LEDs, read analog values from the integrated ADC, and stream accelerometer data. Be sure to see it in action after the break!

We could see this project being expanded to run on the Raspberry Pi with a multitude of sensors. What will you add a web interface to next? Home automation? A weather station? Let us know!

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Robot Cage Fighting Is Still A Thing!

April 4, 2014 by James Hobson 25 Comments

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Remember Battlebots? Turns out it is alive and well in Southern California at the National Tooling and Machining Association (NTMA) Robotics League. That’s right — high school students are getting to build remote controlled weaponized robots to battle to the death inside a poly-carbonate octagon arena. Awesome.

[Bradley Hanstad] wrote to us today to inform us of the 2014 Regional Competition — happening tomorrow at 10AM (PDT). We can’t make it there ourselves, but there is a live stream for everyone to see!

The league started just this fall which currently consists of 15 area high schools, community colleges, and technical schools. The goal of the league is to spark an interest in engineering and manufacturing in young students, while at the same-time providing hands-on education on the applied side of the sciences. It’s sometimes tricky to get students engaged in engineering competitions — but as soon as you say fighting robots you will have most peoples’ attention.

To see a teaser trailer for what is to come at these competitions, stick around after the break!

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Powering A RPi With Hydrogen

April 4, 2014 by Eric Evenchick 23 Comments

Looking for a new way to power your Raspberry Pi? The raspberryHy project aims to develop a small fuel cell designed for powering the credit card sized computer. It adds a proton exchange membrane (PEM) fuel cell, a battery, and custom control electronics to the Pi.

The system takes hydrogen in from a compressed hydrogen cartridge and feeds it through a regulator. This passes the hydrogen into the PEM fuel cell at the correct pressure, and creates a potential. The control electronics boost that voltage up to the 5 V required on the Pi’s USB port. There’s also an electronically controlled purge valve which periodically exhausts the fuel cell.

There’s a few reasons you might want to run your Pi with hydrogen. Run time of the fuel cell is limited only by the amount of hydrogen you can store. In theory, you could connect a large cylinder for very long run times. Combined with a battery, this could be quite useful for running Pis in remote locations, or for long-term backup power. The raspberryHy will be presented at Hannover Fair 2014 this month.