Monitoring water levels with a Parallax Ping sensor


When you need a mechanism to detect the water level within a container or tank, you have several different options. Most people opt for a simple float or probe that sits in the water, while others use optics to sense when the water is reaching an undesired level.

This device built by [Danilo Abbasciano] uses a Parallax Ping sensor instead. If the sensor is placed at the top of a well, cistern, or other water container, it can accurately calculate the height and volume of the fluid inside. This is done by using the Ping’s readings in conjunction with a few values already known to the user, namely the dimensions of the container.

In his implementation, the readings are relayed to a simple LCD panel for easy viewing, and a small piezo speaker is used to sound an alarm when the water level reaches a predefined threshold. This sort of measuring device can be quite useful in situations where a contact-based sensor would be subject to chemicals and corrosion, or where contamination is a concern.

We don’t need to brainstorm projects; xkcd does that for us

[Randall Munroe], the guy behind our favorite web comic xkcd, gave us yet another great project idea that falls on the heels of securing our valuables and silencing loud car stereos. The xkcd forum has been talking about how to implement this, and we’d like to hear what Hack A Day readers think about this idea.

The project isn’t much different from 3D photography. [Carl Pisaturo] has done a lot of art and experimentation based on this idea that basically amounted to largish binoculars. A poster on the xkcd forum has already built this using mirrors, but we’re wondering how much the parallax can be increased with this method. Two cameras and a smart phone would also allow automatic pan and tilt that corresponds to head movement.

We’re not quite sure if this idea can be applied to astronomy. The angular resolution of the human eye is around one arc minute, every star except for the Sun has an annual parallax less than one arc second. If anyone wants to try this out with a longer baseline (From Earth to Pluto for example), we would suggest simulating this in Stellarium. Seeing the moon as a sphere would be possible with a few hundred miles between cameras, though.

Tell us how you would build this in the comments, and be sure to send in your write-up if you manage to build it. We’ll put it up right away.

Thanks to [Theon144] for sending this in.

EDIT: Because the comments are actually bearing fruit, check out the thread on the Hack A Day forums for this post: link.

Meet Radio Shack’s new Parallax lineup

It looks like Radio Shack is pretty serious about their new found commitment to their focus on the DIY, inventor, creator and geek demographics. [Ken Gracey], Parallax forum guru, put up a post on the Parallax stuff that will be sold at Radio Shack. Everything is priced, “below spousal approval level,” but no word on what those prices are.

Here’s the (probably not conclusive) list we gleaned from the pics: 2-axis joystick, gyroscope, GPS, compass and altimeter modules, an infrared sensor, 2×16 backlit LCD, BASIC stamp 2 board, and an XBee 2-pack that we assume would be priced above girlfriend approval levels.

We’re curious about how many (and in what quantity) of these items will be stocked at the East Nowheresville strip mall, and again there’s no mention of improving the selection of individual components.

At Hack A Day, we were thinking how amazing a Radio Shack ‘component vending machine’ would be. A modified pick and place machine that will dole out caps, resistors, other components, and has the potential to be competitive with online stores. Anyone feel like sending that suggestion in?

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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