To test his new skills with his Arduino, [Ben] decided that he would build a robot. With no particular need to fill other than the need to build something cool he chose to build himself a tree climbing robot. He designed the body of the robot in Google Sketchup before beginning the build. The body is made mainly from aluminium, with four motors for the gripping legs and one for the spine. [Ben] controlled the motors with the familiar L298 motor driver chip and measured their position and speed using some cleverly mounted potentiometers.  The robot can climb trees of varying diameter by using the speed of the motors driving the legs to determine when the tree has been gripped.

[Ben] was then kind enough to write up a full instructable describing the build, this project includes a bit of everything, from motor control and liner drives to tips on creating a robot frame; a good read for someone wanting to get into robotics. Also check out the video after the break to see the robot in action.

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[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.

[Rumplestiltskin] has had work done on his double-hung windows to help prevent drafts and keep them in good working order. But there are still a few that rattle, and let in the cold of winter. Not this year; he’s added a small feature to the jamb that will keep out the cold weather.

A pair of jointing blocks were added to each window. The small block seen above is attached to the window jam with a couple of all-purpose screws, and hosts a machine screw which points toward the window frame. Since there is weather stripping between the two window frames, and between the frame and the outer jamb, tightening this screw will snug the frames up to close any small gaps. This has the unintended consequence of prohibiting the window from being opened (unless you don’t mind scraping the paint as the machine screw slides across the wood). But if only used in the winter months this is a viable solution.

We hate to admit it, but we missed out on the TI Chronos watch deal last week. While we’re still a little bit burned over the fact that these watches sold out so fast, [Ahmet] sent in his Open Source Bluetooth Watch and we’re thinking this could eventually be a decent replacement.

The watch is built around an Arduino Pro Mini, a scavenged Nokia LCD, and a BlueSMiRF Gold. The Bluetooth connects to a Nokia N900 with a little Bluetooth client app [Ahmet] wrote. He also wrote a small GUI for the watch’s LCD display. Afterwards, he was able to display missed calls, new email, and is now working on support for changing songs on his N900′s media player.

Admittedly, a little work needs to be done on the enclosure. Still, the potential for this watch is much greater than the iPod as a watch project we saw last year. Right now, we’re thinking about what could be added to [Ahmet]‘s watch. An accelerometer would probably be on the top of our list, but if you have any ideas feel free to leave them in the comments.

Check out the walk through of the watch’s functions after the break.

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Dippy birds are the toys that teeter-totter back and forth as the beak of  bird-shaped body dips into a container of water. The felt covering the beak and head picks up water and, through evaporation, cools that end of the glass tubing. The temperature changes cause the dichloromethane to either boil off, or condense, shifting the weight of the liquid thereby pivoting the glass body.

The real question is, does the temperature of the water cause the toy to move differently, and can that be measured to calculate the temperature of the water? [Craig] put that query to the test, by designing an apparatus to measure the motion of a Dippy Bird. A photointerruptor was used to measure the motion of the body, causing an interrupt each time the tail of the bird passes in between the sensor and the emitter. For control data a DS1820 temperature sensor was positioned near the felt on the head of the bird, and a relative humidity sensor captured readings at the same time. Data from the three inputs was collected over a two-day period. Although not a precise measurement, the motion of the bird did trend in the same ways that were recorded by the temperature and relative humidity sensors.

Continuing on with our high-voltage theme, today we have a page describing Marx generators by [Grenadier]. Marx generators are devices that produce pulses of very high voltage with fast rise times. For most of us, that means that they can make neat sparks. For the more serious types out there, that also means that they are great for driving some high-powered lasers, simulating lightning strikes, and even igniting the conventional explosives surrounding the core of a nuclear weapon! His page includes a video of his Marx generator producing some pretty sparks for those of us who aren’t so serious.

We have featured several of [Grenadier's] projects in the past. This one doesn’t deviate from his normal style of taking a subject and clearly describing it with lots of well-taken pictures.

Recently, he has been working on improving one of his projects that deviates from what he normally does. He is calling it “The Junkbox”. The Junkbox is something like a free online swap meet where you can sell your electronic parts.

This bar code tattoo was sent into us by [Lifespan]. Before going under the needle, [Lifespan] didn’t care much for tattoos. After seeing this video he realized that a tattoo could have dynamic content through domain redirection.

[Lifespan] spent a lot of time going over the different styles of 2D bar codes. QR codes were deemed ugly because of the three large squares in the corners. An EZ Code, like the one in his YouTube inspiration, are a proprietary format that must be read with a ScanLife app. He eventually settled on a Data Matrix bar code because of its open format and ubiquity in business and industry. To make the tattoo dynamic, [Lifespan] made the tattoo point to 5id5.com. With a little bit of smart phone wizardry, that domain can be redirected to any URL in a moments notice.

Like all well-planned tattoos, he found himself a very good artist to do the piece. [Connor Moore] managed to ink some skin at 15 dpi, which was a little risky, but the results came out great. While it’s not scarification via a laser cutter, barring fading this tattoo is technologically future proof.

[Leafcutter] is big in to making music and has put together all sorts of musical instruments and tools over the years. Recently, he was inspired to make his own piezo crystals, and wrote in to share the results of his experiments with us.

[Leafcutter] is no stranger to messing around with piezo elements, and after seeing [Collin’s] tutorial on making your own piezo crystals at home, he knew he had to give it a try. He stopped by the grocery store to fetch all of the ingredients, then followed [Collin’s] instructions to the letter…well, almost. It seems that he might have cooled the solution too quickly, so he found himself with a jar full of tiny, barely usable piezo crystals instead of larger ones like [Collin] was able to produce.

Undeterred, he decided to see if the stuff was any good, and rigged up a makeshift contact microphone using some conductive foil and a clamp. He piped the output to his amplifier, and wouldn’t you know it…it worked!

He has a small sound clip of what the mic sounded like on his site, and it worked pretty darn well despite the crystal’s tiny size. He is going to give the whole process another go, so we hope to see more experiments with bigger crystals in the near future.