Throwing Pis into the Stratosphere

It’s always exciting to see the photos from High Altitude Ballooning (HAB) outings. While it’s no surprise that the Raspi is a popular choice—low cost, convenient USB jacks, etc.—this is the first build we’ve seen that uses an OLED during the trip to show real-time data on-screen to be picked up by the on-board webcam. (Though you may have to squint to see it at the bottom middle of the above image).

[Fabrice’s] payload made it to 26,000m, and the screen he chose, an ILSOFT OLED, performed admirably despite the extreme conditions suffered (temperatures can reach -50C). The last time we saw a near-space Raspi payload was a couple of years ago, when [Dave Akerman] was closing in on UK balloon altitude records. [Dave] hasn’t stopped launching balloons, either, testing new trackers and radio modules, as well as his most recent build that sent a Superman action figure to the skies—all recorded in glorious HD.

Check out both [Dave] and [Fabrice’s] blogs for loads of pictures documenting the latest in High Altitude Ballooning, and stay with us after the jump for a quick video of [Fabrice’s] OLED in action.

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$2 FM Transmitter for Raspberry Pi

We love re-purposed consumer gear. [Tobias] sent us the link to his project to that uses a cheap, discontinued cellphone gadget to create a Raspberry Pi controlled FM radio transmitter.

The Sony-Ericsson MMR-70 radio transmitter apparently used to connect to a cell phone and broadcast music. But the Walkman cellphones in question are a little bit old in the tooth, so one can buy the transmitter units for cheap on the resale market. What makes the transmitters even more interesting is that you can activate and deactivate the radio, change frequency or output power, and even send RDS station and song information.

It turns out (link in German) that the radios have an AVR ATMega32 microcontroller and a NS73 radio transmitter module, which can be entirely controlled over I2C. (Schematic here as PDF.) The units also have handy test points strewn all around. Once the test points were mapped out, one could completely ignore the on-board AVR microcontroller and control the FM transmitter module directly using the Raspberry Pi’s I2C outputs.

And that’s where [Tobias] stepped in. He wrote an I2C daemon for the Raspberry Pi that lets you control the FM transmitter via simple commands. All you have to do is solder up a bunch of test points, install [Tobias]’s software, write a batch script, and you’re on the air. For instance, this makes building a FM radio retransmitter for online streamed audio a one-day project. You can see his working example on youtube. Of course, you’ll want a web-based remote control interface to go with that.

If you’re interested in hacking along, and don’t have a Raspberry Pi application in mind, Sparkfun used to sell the NS73 radio transmitter so you can find lots of good information about the chip. We’d love to see a stand-alone broadcasting gizmo that actually utilizes the onboard AVR chip, but our hats are off to [Tobias] for making the Raspberry Pi version so accessible.

“Stomach Shot” Halloween Costume

Halloween may have come and gone, but [Luis] sent us this build that you’ll want to check out. An avid Walking Dead fan, he put in some serious effort to an otherwise simple bloody t-shirt and created this see-through “stomach shot” gunshot wound.

The project uses a Raspi running the Pi Camera script to feed video from a webcam on the back of his costume to a 7″ screen on the front. [Luis] attached the screen to a GoPro chest harness—they look a bit like suspenders—to keep it centered, then built up a layer of latex around the display to hide the hard edges and make it more wound-like. Power comes from a 7.4V hobby Lipo battery plugged into a 5V voltage converter.

After ripping a small hole in the back of his t-shirt for the webcam and a large hole in the front for the screen, [Luis] applied the necessary liberal amount of fake blood to finish this clever shotgun blast effect.

The Raspberry Pi Model A+

A few months ago we were lucky to get the scoop on a new Raspberry Pi a few days before it was officially announced. This model ended up being the Raspberry Pi Model B+, with improvements that included more USB ports, not-dumb mounting holes, more GPIOs, and a decent microSD card connector. Today, we’re proud to leak another revision to the Raspberry Pi ecosystem – the Raspberry Pi Model A+

There really aren’t many details for this new revision of the Raspi, but we can make some educated guesses. The new model features the same not-dumb mounting holes as the B+, 58mm wide by 49mm wide. All the ports are moved to two sides of the board, and the analog audio and video are combined into one 3.5mm jack. Like the normal Model A, this one doesn’t have Ethernet and only one USB port, but the improvements seen from the B to the B+ are still there: a good microSD card socket is on the back, and the 40-pin GPIO header replaces the old 26-pin header. There’s no word if the A+ will feature a RAM upgrade – when the Model B was ramping up production The Foundation decided to bump the RAM up to 512MB. This could happen with the A+, but we’re not holding our breath.

There’s no word when the A+ will be announced, or when it will start shipping. The educated guess would say tomorrow morning, with an analysis of how much power this thing consumes a week after it starts shipping.

Deck the Halls with a Raspberry Pi Controlled Christmas Tree

You know the holiday season is getting close when the Christmas light projects start rolling in! [Osprey22] is getting a jump on his holiday decorations with his Christmas Tree light show controlled by a Raspberry Pi. Yes, we know he could have done it with an Arduino, or a 555, but the Raspi makes for a convenient platform. With a WiFi module, code changes can be made remotely. The Raspberry Pi’s built-in audio interface also makes it easy to sync music to flashing lights, though we’d probably drop in a higher quality USB audio interface.

[Osprey22’s] Raspberry Pi is running his own custom python sequencer software. It takes an mp3 file and a sequence file as inputs, then runs the entire show. When the music isn’t playing, the Pi loops through a set of pre-defined scenes, changing once per minute.

The hardware itself is pretty straightforward. The Raspberry Pi controls 8 solid state relays through its GPIO interface. 8 strings of lights are more than enough for the average tree. [Osprey22] topped the tree off with a star made of wood and illuminated by a string of 25 WS2801 RGB LED pixels.

Click past the break to see [Osprey22’s] tree in action!

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Fox Hunting with a Raspberry Pi

No, not a real fox! [KM4EFP] is a ham radio operator with a passion for fox hunting, which is an event where several radio operators attempt to find a broadcasting beacon (a “fox”) using radio direction finding techniques. [KM4EFP] has just built his own portable fox using a Raspberry Pi in a very well-built enclosure.

Since the fox could be outside for a while, the project was housed in a reasonably weatherproof ammunition case. A mount for an antenna was attached to the side, and it is hooked up to a GPIO pin on the Raspberry Pi. The entire device is powered by a 6000 mAh battery pack which allows the fox to broadcast long enough to be found.

The software running on the Raspberry Pi is very similar to the Pi FM transmitter program but it is specially made for ham radio broadcasting instead. Almost no extra hardware is needed to get the Pi broadcasting radio, as these software packages can drive the antenna directly from the GPIO pin. This is a great twist on the standard FM transmitter that ham radio enthusiasts everywhere can use to start finding those wily foxes!

Nixies and Raspis for a Modern Vintage Calculator

There are a few very rare and very expensive calculators with Nixie tube displays scattered about calculator history, but so far we haven’t seen someone build a truly useful Nixie calculator from scratch. [Scott] did just that. It’s a complete, fully-functional electronic calculator with all the functions you would expect from a standard scientific calculator.

The calculator uses IN-12 Nixies, the standard for anyone wanting to build a clock or other numerical neon discharge display. Each Nixie is controlled by a K155D driver chip, with the driver chip controlled by an I2C IO expander.

The keypad is where this gets interesting; electronics are one thing, but electromechanicals and buttons are a completely new source of headaches. [Scott] ended up using Cherry MX Blue switches, one of the more common switches for mechanical keyboards. By using a standard keyboard switch [Scott] was able to get custom keycaps made for each of the buttons on his calculator.

The brains of the calculator is a Raspberry Pi, with the I2C pins going off to listen in on the several IO expanders on the device. A Raspi might be a little overkill, but an Internet-connected calculator does allow [Scott] to send calculations off to WolframAlpha, or even the copy of Mathematica included in every Pi.

[Scott] has put his project up on Kickstarter. Videos below.

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