Printing Text with a Chart Recorder

A chart recorder printing 'Hello World'

Chart recorders are vintage devices that were used to plot analog values on paper. They’re similar to old seismometers which plot seismic waves from earthquakes. The device has a heated pen which moves across a piece of thermally sensitive paper. This paper is fed through the machine at a specified rate, which gives two dimensions of plotting.

[Marv] ended up getting a couple of discontinued chart recorders and figured out the interface. Five parallel signals control the feed rate of the paper, and an analog voltage controls the pen location. The next logical step was to hook up an Arduino to control the plotter.

However, once the device could plot analog values, [Marv] quickly looked for a new challenge. He wanted to write characters and bitmaps using the device, but this would require non-continuous lines. By adding a solenoid to lift the pen, he built a chart recorder printer.

After the break, check out a video of the chart recorder doing something it was never intended to do. If you happen to have one of these chart recorders, [Marv] included all of the code in his writeup to help you build your own.

[Read more...]

The Radius T-T Velomobile

The Radius T-T Velomobile human powered vehicle


Over the past year, [Dave] has been hard at work on his human powered vehicle. One year and six hundred hours of build time later, the Radius T-T Velomobile is complete. This 80 lb. vehicle features a custom body, mirrors, and integrated lights.

The Radius T-T started out as a TerraTrike recumbent tricycle. [Dave] built the body by laying up fiber glass on a foam mold. To that he added a variety of 3D printed accessories such as lights and mirrors. Inside the cockpit, the driver can control turn signals and flashers.

[Dave]‘s blog provides a massive amount of documentation on the build. Everything from 3D modelling of the vehicle in Blender to the rear view mirror design is discussed. This great looking build should move along quickly with its lightweight design, but we’re still waiting to hear how fast it goes. Either way, it should be a fun mode of transport which will definitely turn some heads.

CERN Shows Off New KiCad Module Editor

Photo from video demo of new KiCad module editor

CERN, the people that run a rather large particle collider, have just announced their most recent contributions to the KiCad project. This work focused on adding new features to the module editor, which is used to create footprints for parts.

The update includes support for DXF files, which will make it easy to import part drawings, or use external tools for more complex designs. New distribute tools make it easy to space out pads evenly. The copy and paste function now allows you to set a reference point, making it easy to align blocks. Finally, the pad enumeration tool lets you quickly set pin numbers.

CERN has already implemented a new graphics engine for KiCad, and demonstrated a new push and shove routing tool. The work plan for CERN’s KiCad contributions shows their long term goals. If you’re interested in what CERN is doing with KiCad, you can check out the CERN KiCad Developers Team on Launchpad.

After the break, watch a quick run through of the new features.

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Carpool DeVille: The World’s Fastest Hot Tub

The Carpool DeVille Hot Tub Car

Back in 1996, a group of engineering students at McMaster University set out to build a fully functional hot tub housed in a working car. They chopped up an abandoned 1982 Chevy Malibu and converted it into The Carpool.

That group of students graduated, and began work on the Carpool DeVille. Six years later, they’re ready to take it to Bonneville Salt Flats to claim the title of “world’s fastest hot tub.”

There has been some substantial modifications to the vehicle to make the Carpool a reality. A custom fibreglass tub was built to drop into the passenger compartment, and heat exchangers were added to the stock engine system to heat the water. The plumbing and pumps for the tub reside in the truck, while the original V8 engine is up in the front. A custom air suspension system allows them to carry the massive volume of water. There’s even a marine throttle to control gas and brake from the driver’s seat in the tub.

The folks behind the Carpool DeVille ran a Kickstarter to fund their race costs. The campaign is over, but you can still check out the story and pictures of the conversion. Since it was a successful campaign, we’re looking forward to seeing this custom vehicle out on the salt flats.

Proper Debugging for Energia Sketches

Moving a sketch from Energia to Code Composer Studio

Energia is a tool that brings the Arduino and Wiring framework to Texas Instruments’ MSP430 microcontrollers and the MSP430 Launchpad development board. This allows for easy development in an Arduino-like environment while targeting a different microcontroller family.

One problem with Energia and Arduino is the difficulty of debugging. Usually, we’re stuck putting a Serial.println(); and watching the serial port to trace what our program is doing. Other options include blinking LEDs, or using external displays.

Code Composer Studio, TI’s official development tool, allows for line-by-line debugging of applications. You can set breakpoints, watch the value of variables, and step through an application one instruction at a time.

The good news is that the latest version of Code Composer Studio supports importing Energia sketches. Once imported, you can step through the code and easily debug your application. This is a huge help to people developing more complex software using Energia, such as libraries.

TI gives us an overview of the new feature in a video after the break.

[Thanks to Adrian for the tip!]

[Read more...]

Pi Musicbox 0.5 Released

Pi MusicBox Logo


Have an extra Raspberry Pi kicking around? Pi MusicBox provides a way to quickly turn it into a standalone streaming device that can fetch music from tons of sources. The latest release of Pi MusicBox adds a bunch of new features.

We took a look at this software over a year ago, and noted that it made streaming Spotify easy, and had support for controlling tracks using Music Player Daemon (MPD). The newest release supports AirPlay, DNLA, Google Music, SoundCloud, and several other music sources.

Since the analog audio output on the Pi isn’t great, Pi MusicBox includes support for a variety of USB sound cards. It’s also possible to use the HDMI port for digital audio output, which can be connected into your home theatre system.

If you want to build a standalone music device, this looks like a great place to start. The user community has built a variety of projects that run this software, which are featured on the Pi MusicBox homepage.

Android Doorbell Notifier

Breadboarded circuit to detect when doorbell rings

It’s always unfortunate to find a FedEx tag on your door saying you missed a delivery; especially when you were home the whole time. After having this problem a few times [Lee] decided to rig up a doorbell notifier for his Android phone.

[Lee]‘s doorbell uses a 10 VAC supply to ring a chime. To reduce modifications to the doorbell, he added an integrated rectifier and a PNP transistor. The rectifier drives the transistor when the bell rings, and pulls a line to ground.

An old Netgear router running OpenWRT senses this on a GPIO pin. Hotplugd is used to run a script when the button push is detected.

The software is discussed in a separate post. The router runs a simple UDP server written in C. The phone polls this server periodically using SL4A: a Python scripting layer for the Android platform. To put it all together, hotplugd sends a UNIX signal to the UDP server when the doorbell is pushed. Once the phone polls the server a notification will appear, and [Lee] can pick up his package without delay.


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