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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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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Recording Time Lapse of Endangered Reptiles Hatching

The tuatara is a reptile native to New Zealand, and thanks to the descendants of stowaway rats on 17th century ships, these little lizards are critically endangered. [Warren] was asked if he could film one of these hatchlings being born and pulled out a Raspberry Pi to make it happen.

[Warren] constructed a small lasercut box to house the incubating egg, but he hit a few snags figuring out how to properly focus the Raspi camera board. The original idea was to use a Nikkor macro lens, without any kind of adapter between it and the camera board. A bit of googling lead [Warren] to this tutorial for modifying the focus on the Raspi camera, giving him a good picture.

The incubator had no windows and thus no light, making an IR LED array the obvious solution to the lighting problem. Time was of the essence, so an off-the-shelf security camera provided the IR illumination. After dumping the video to his computer, [Warren] had a video of a baby tuatara hatching. You can check that out below.

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A Tiny Arcade Machine With Tinier Buttons

Building a MAME machine around a Raspberry Pi has been the standard build for years now, and tiny versions of full-sized arcade machines have gone from curiosity to commonplace. [diygizmo] just built one of these tiny arcades, but the fit and finish of this one puts it above all others. There’s a real, miniature joystick in there, along with 3D printed adapters for tact switches to make this one look like a lilliputian version of a full size standup MAME cabinet.

The entire enclosure is 3D printed, and most of the electronics are exactly what you would expect: A Raspberry Pi, 2.5″ LCD, and a battery-powered speaker takes up most of the BOM. Where this build gets interesting is the buttons and joystick: after what we’re sure was a crazy amount of googling, [diygizmo] found something that looks like a normal arcade joystick, only smaller. Unable to find a suitable replacement for arcade buttons, [diygizmo] just printed their own, tucked a tact switch behind the plastic, and wired everything up.

Add in some decals, paint, and the same techniques used to create plastic model miniatures, and you have a perfect representation of a miniature arcade machine.

Stereo Vision and Depth Mapping with Two Raspi Camera Modules

The Raspberry Pi has a port for a camera connector, allowing it to capture 1080p video and stream it to a network without having to deal with the craziness of webcams and the improbability of capturing 1080p video over USB. The Raspberry Pi compute module is a little more advanced; it breaks out two camera connectors, theoretically giving the Raspberry Pi stereo vision and depth mapping. [David Barker] put a compute module and two cameras together making this build a reality.

The use of stereo vision for computer vision and robotics research has been around much longer than other methods of depth mapping like a repurposed Kinect, but so far the hardware to do this has been a little hard to come by. You need two cameras, obviously, but the software techniques are well understood in the relevant literature.

[David] connected two cameras to a Pi compute module and implemented three different versions of the software techniques: one in Python and NumPy, running on an 3GHz x86 box, a version in C, running on x86 and the Pi’s ARM core, and another in assembler for the VideoCore on the Pi. Assembly is the way to go here – on the x86 platform, Python could do the parallax computations in 63 seconds, and C could manage it in 56 milliseconds. On the Pi, C took 1 second, and the VideoCore took 90 milliseconds. This translates to a frame rate of about 12FPS on the Pi, more than enough for some very, very interesting robotics work.

There are some better pictures of what this setup can do over on the Raspi blog. We couldn’t find a link to the software that made this possible, so if anyone has a link, drop it in the comments.

A Full IP Webcam With a Raspberry Pi

A Dropcam will run you about $150. Price out a Raspberry Pi, camera sensor, and a CCTV camera housing found on eBay, and it starts to look like there may be a cheaper replacement for a Dropcam sitting around on workbenches, if only someone can figure out the software. [Antoine] did just that, giving any Raspberry Pi the ability to stream H.264 video over a network.

[Antoine]‘s software is based on the raspivid tool distributed from the foundation, but that only takes care of capturing and encoding H.264 video from the camera sensor. To add IP camera support, the Live555 RTSP library was mixed in and combined to stream video over the Raspi’s network connection.

With a camera dome enclosure from the usual outlets, [Antoine]‘s project really starts to look professional. The specs are respectable, too: it can output a 1080 stream, and with a small modification to an Ethernet cord, this webcam has PoE. Future updates include the ability to record videos based on a trigger and possibly a webserver on the Pi for configuration. [Antoine] says he really isn’t up to speed with Javascript, so any help would be appreciated.

Turning the Raspberry into a CAD Workstation

Inventables has been working hard on a successor to the extremely popular Shapeoko CNC milling machine, and to bring digital fabrication to the masses, they’ve created Easel, possibly the easiest 3D design software you’ll ever use. [Sacha] was trying out the beta version of Easel and mentioned to the dev mailing list he was running his installation on a Raspberry Pi. One of the developers chimed in, and after a bit of back and forth we now have a workflow to use Easel with the Raspberry Pi.

Easel is a web app, but since the graphics, design, and g-code generation are handled locally, even the most rudimentary CAD suite would choke the decidedly low power Raspi. Instead, [Sacha] is using the Raspberry to grab 2D and 3D files, turn that into g-code for a machine, and send it off to a Shapeoko router.

Easel doesn’t yet have local sender support that works on Linux, so a separate piece of software is used to shoot the g-code over a serial port to the machine. That’s something that will probably be added in a later version of Easel, making a Raspberry Pi a great way to control router or milling machine.