Etch-a-Sketch automatically draws a tribute to Hack a Day


We have seen quite a few automated Etch-a-Sketch machines in our time, but when [Jason] wrote in to share his take on the subject, it came with a nice bribe attached. We are vain. It’s not something we are proud of, but when it comes to seeing the Hack a Day logo drawn out by a robot, consider us sold.

[Jason] has several CNC router builds under his belt, and thought it would be fun to automate his Etch-a-Sketch, a toy he loved as a child. He cut some gears and a face plate for the toy with his new CNC machine, then got busy programming his Propeller microcontroller to do his bidding.

A piece CNC software handles the conversion of a bitmap image to an outline, which is then converted to a CNC cutting path. The cutting path is translated into x/y coordinates by a bit of C++ code, before being fed into the microcontroller, which is running a small SPIN application he calls RoboSketch. The Propeller takes care of the rest, quickly drawing the image or pattern to the Etch-a-Sketch.

Continue reading if you would like to see a video of [Jason’s] tribute to Hack a Day, and don’t miss some of our previous automated Etch-a-Sketch coverage if this is something on your to-do list.

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Robotic gardener takes its cue from bomb disposal bots

[Dave] posted some pictures and videos of his ‘Nuntius’ robot on the Propeller forums. From the pictures it’s an impressive build, but to really appreciate [Dave]‘s skill, check out the Youtube demo.

The controller is a Propeller protoboard with bits of angle aluminum fastened together. Pots are positioned at the joints of the remote’s arm so the robot’s arm can mirror the shape of the remote. We usually see Armatron bots controlled via computer, or in the rare case of human control, a mouse. [Dave]‘s build just might be one of the first remote manipulator builds we’ve seen on Hack A Day.

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Propeller-based robot with basic object avoidance


The Parallax Propeller is a pretty powerful MCU as [Dino] recently discovered in his latest Hack a Week installment. He wanted to build a simple robotics platform that he could use for testing out various sensors, and he figured he might as well learn about a different type of micro controller in the process.

He pieced together his robot using a pair of old Roomba motors he had sitting around, mounting them on a standard RadioShack project box. A Propeller MSR1 control board runs the show, and a Propeller PING sensor is used to get an idea of what the robot’s surroundings look like. He is an admitted newbie when it comes to using Propeller micro controllers, but [Dino] was able to give his robot some rudimentary object avoidance abilities fairly easily. A few small bugs aside, he had the robot up and running in short order, a testament to how easy it is to work with the Propeller platform.

Stick around to see a brief video covering the robot’s construction we have embedded below.

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Digital Audio on the Parallax Propeller

[Beth] had the idea for transmitting digital audio over S/PDIF on a Propeller a few years ago, but only just got around to a writeup. For that, we thank her.

The writeup has a marvelous walkthrough of the S/PDIF protocol and the problems associated with with generating the signal. S/PDIF is a relatively resource-intensive protocol – the signal is clocked at 64x the audio sample rate. That signal is doubled for biphase mark code, keeping everything in sync. [Beth] says the microcontroller would neet at least 24 MIPS of processing power just to generate the S/PDIF signal – processing audio would be another task altogether. Because of the processing power needed, and the weird clock rates needed, [Beth] decided to go with the Propeller. The implementation uses only one core of the Propeller, leaving another seven cores available for sound synthesis or even a visualization over VGA.

[Beth] admits this could be done with just about any microcontroller (although it would need to be clocked at a multiple of 4.096 MHz for a 32kHz audio stream), but we really appreciate the work that went into bit-banging this signal.

Video of [Nick] at Gadget Gangster playing around with digital audio on a Propeller after the break.

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Propeller proto board has you flying in no time


[Parker] was in need of a Propeller development board to make working on his projects easier. More often than not, when he needed to prototype something, he would pull the only one he had on hand from his home made pinball machine, and replace it when finished. This was time consuming and cumbersome, so he decided he needed a better way of doing things.

He looked into purchasing a Gadget Gangster proto board which allows you to use a Propeller much like an Arduino, complete with support for shields and the like. Unfortunately, they were sold out and he was in a hurry to finish up a project. Rather than wait, he decided to build his own proto board, which would be more flexible than the COTS version – allowing him to add things like an Analog to Digital converter without having to use a shield.

He looked around online and found some schematics to follow, and had his proto board constructed in no time. It gets the job done and looks quite clean, considering it was put together using perf board.

Keep reading to see a video walkthrough of the Propeller development board construction.

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Remote-controlled tank tread robot will walk the dog for you


Instructables user [IAMTHEBOT] recently finished building his robot which can be controlled by a human using an R/C transmitter, via a PC, or through its built-in object avoidance system. The robot doesn’t seem to have a name, though Johnny Five might be appropriate.

The robot was built using plenty of erector set parts, as well as a Lynx motion tank tread kit. The robot is crammed full of controllers, including a Propeller USB servo controller which operates the arms, and a pair of Parallax motor controllers to manage the tread movement. A pair of Parallax Stamp controllers are used to drive these controllers as well as to manage the remainder of the robot’s functions.

The robot’s head consists of a custom pan and tilt wireless camera system, which allows him to drive it around from the comfort of his home, while watching the video stream on his PC. The robot also has the ability to roam around autonomously, avoiding objects using a ping sensor that can be mounted where the camera is currently located. It seems all that’s missing is Steve Guttenberg.

As you can see in the videos below, the robot manages pretty well on all sorts of surfaces, and even walks this guy’s dogs.

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What Development Board to Use? (Part Two)

We asked for responses to our last Development Board post, and you all followed through. We got comments, forum posts, and emails filled with your opinions. Like last time, there is no way we could cover every board, so here are a few more that seemed to be popular crowd choices. Feel free to keep sending us your favorite boards, we may end up featuring them at a later date!

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