Like most hackerspaces, when the folks at DIYode, the Guelph, Ontario hackerspace, aren’t in the workshop, they’re on IRC. It’s a great way to build a community, complete with a bot that collects and catalogues to-do items, meeting topics, posts events to IRC, and even does a bit of text-to-speech so members currently at the DIYode can listen in on the IRC room. There’s also a webcam for the DIYode space that members check constantly. [Simon] thought it would be a great prank to freak out those members that constantly check the webcam, and we’ll say he succeeded with a little help from the Alabama Face Guy.
The build listens for a specific phrase in the IRC room – “Hey, someone just entered the shop without the doorbot noticing” – and sends a command via Python to an Arduino to raise and lower a cardboard cutout of a sneering face in front of the web cam. For an April Fool’s build, this is probably one of the most creative and creepy we’ve seen this year.
[Ivan] made something special with this car stereo hack. He altered the head unit to play MP3 files from USB and added an auxiliary line-in. But looking at it you’d never know. That’s thanks to the work he did to create a false button hiding the audio jack, and a false cassette hiding the USB port and MP3 player display. Possibly the best part is that the radio itself still works like it always did.
There are several components that went into making the system work. It starts with the cassette/radio head unit. To that he added an MP3 player with remote which he picked up on Deal Extreme. He wasn’t a huge fan of the IR remote that came with it so he rolled in a remote that mounts on the steering wheel. To pull everything together he used a PIC 16F877a. The microcontroller controls the lines which tell the head unit if a tape has been inserted. When [Ivan] selects either the Aux input or wants to play MP3s from a thumb drive the uC forces the head unit into cassette mode and the audio from the player is injected into the cassette player connections.
To help deter theft [Ivan] created two false fronts. The end of a cassette tape plugs into the USB port. The rewind button plugs into the Aux jack. You can get a good look at both in the demo after the break.
Continue reading “MP3/USB/Aux hack hidden behind cassette facade”
Here’s a really quick video which takes a different approach to understanding the Fourier Series than we’re used to. If you’re a regular reader we’re sure you’ve heard of the Fourier Series (often discussed as FFT or Fast Fourier Transform), but there’s a good chance you know little about it. The series allows you to break down complex signals (think audio waves) into combinations of simple sine or cosine equations which can be handled by a microcontroller.
We’ve had that base level of understanding for a long time. But when you start to dig deeper we find that it becomes a math exercise that isn’t all that intuitive. The video clip embedded after the break changes that. It starts off by showing a rotating vector. Mapping the tip of that vector horizontally will draw the waveform. The Fourier Series is then leveraged, adding spinning vectors for the harmonics to the tip of the last vector. The result of summing these harmonics produces the sine-based square wave approximation seen above.
That’s a mouthful, and we’re sure you’ll agree that the video demo is much easier to understand. But the three minute clip just scratches the surface. If you’re determined to master the Fourier Series give this mammoth Stanford lecture series on the topic a try.
Continue reading “Retrotechtacular: The Fourier Series”