Android controlled t-shirt cannon

Every year, Qualcomm hosts the “Battle of the Schools.” This year the goal was to build homemade contraptions that would be judged on how cool they are. [Doug DeCarme], [Shaver Deyerle], and [Zach Rattner] – three Qualcomm employees at Virginia Tech – built an Android controlled t-shirt cannon for this event and ended up tying with Michigan State for first place.

The cannon is built around an Arduino Uno and a BlueSMiRF Bluetooth modem. [Doug DeCarme], the Android developer of the group, put together an app that would fire each barrel independently. The valves for the cannon are just 150 PSI inline sprinkler valves, bought from the local Home Depot. From the project breakdown, the team spent less than $150 on entire project.

From the video, we see that they’re getting some pretty good distance firing t-shirts at 160 PSI. Although we question the wisdom of using PVC as a pressure vessel holding 160 PSI, changing the PVC to a proper air reservoir wouldn’t be that hard.

VGA Pong on a chipKIT

[Nathan] got his hands on a chipKIT Uno32 development board and wrote a Pong sketch that you can play with a VGA monitor. We love the hardware that makes this feel very much like the classic. It uses a collection of resistor-based digital to analog converters to generate the color signals for the VGA protocol. The score for each player is show on a 7-segment display instead of being printed on-screen. And the paddles are made up of a pair of potentiometers.

You’ll remember that the chipKIT Uno32 is an Arudino compatible 32-bit development board. This project shows how the hardware handles, and how easy it can be to generate VGA signals with it if you know what you’re doing.

For those interested in the game physics themselves, [Nathan] provided a nice explanation about ball movement at the bottom of his post. If you need even more details, dive into the code package that he links to.

Playing DVDs on an iPad

[Harrison Jackson] figured out how to add DVD playback to an iPad. It doesn’t require a jailbreak, or any hardware modifications to your prized tablet. The work is done with some server-side processing and played back through the browser.

The popular open-source multimedia player VLC has the ability to encode from the command line during playback. [Harry’s] option flag mastery of the program allows him to convert a DVD to a 320×240 format that is iPad friendly. But this alone doesn’t get the video any closer to being on the iDevice. You’ll need to be running a webserver that can stream video. This example is on OSX, but since he’s using an Apache server it should be simple to reproduce on any Unix variant. Once you’ve enabled m3u8 files in the Apache mime-types, the iPad browser can be pointed to the file address VLC is kicking out and you’ll be watching a movie in no time.

We’ve wondered about replacing our home theater front-end with an ATV 2 running XBMC but the thought of having no optical drive in the living room requires some contemplation. If this becomes a feasible option (that isn’t downscaled from DVD quality) it will be a no-brainer to make that jump.

Don’t miss the demo video after the break. Full instruction are in the comment section of that clip.

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Building a simple FM transmitter bug

simple_fim_transmitter_hack_a_week

[Dino] got his hands on an FM transmitter “bug” kit via a friend, and thought it would make for an easy and fun Hack a Week project. The kit is simple two transistor half-wave FM transmitter, which the manufacturer suggests could be used to bug a room, hence the name. After poking a bit of fun at the instructions, [Dino] gets to work building the transmitter, wrapping things up in a little less than an hour.

Once he finished soldering everything together, he takes a few moments to test out the bug and to explain how various parts of the board work together in order to transmit the FM signal. He mentions that adding a dipole antenna would make it easy to extend the range of the transmitter, and briefly teases next week’s episode, where he plans on constructing a similar dual-stage transmitter.

This sort of FM circuit is one of the first few simple projects you would see in a beginner’s electronics class, so if you know anyone that is just starting to get their feet wet, be sure to pass this Hack a Week episode along.

Continue reading to see [Dino] explain the ins and outs of his FM bug transmitter.

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Skateboard tagging

We abhor vandalism, but we love art. Here’s a skateboard hack that lets skate punks young and old tag their turf while they ride. [D*Face], a multimedia street artist who grew up in London, added a mounting system to the bottom of his skateboard which includes a can of spray paint. We’re a bit surprised that there’s room enough for that, but the system fits nicely. They’re not locked into a constant stream because the system lets the rider (or a bystander) actuate the spray can via remote control.

But the brush is only one part of the painter’s tool chain. To get the most interesting effect, a pool was painted white to serve as canvas and a troupe of skaters was unleashed on it to try out the modified boards. Check out the video after the break to see the colorful and pleasing curves that result. We just hope nobody bailed and smeared the canvas at the same time.

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