Fixing Misaligned PVC With Kerf Bends

misalignment-coupler

Our old pal [Jeremy Cook] is doing his own remix of [Theo Jansen]‘s Strandbeest, and like the original, he’s using PVC pipe. Unlike the originals, he’s powering it with motors, not wind, and this has caused a few problems in transmitting mechanical power through a piece of PVC. Nothing is perfect, and in a few points in the legs movement the shaft shakes violently. One motor was lost and another nearly so before [Jeremy] came up with a flex coupler made from PVC.

The technique [Jeremy] is using has seen a lot of use with people building laser cut enclosures. It’s called kerf bending, and it works simply by cutting a few slits in a panel that allow it to bend slightly. This technique was replicated by [Jeremy] on a miter saw, cutting eight slots halfway through a one inch PVC pipe, with each successive cut offset 90 degrees.

The new design works well for transmitting power, and he’s not ruining motors any more. Check out the video below.

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Boxing + Arduino + Geometry = Awesomeness

arduino-boxing-blocker

Imagine a machine that [Anderson Silva] could throw a punch at, that would locate his fist in real time and move a punching pad to meet his moving fist. How would you do it? Kinect? Super huge sensor array? Sticking charm? What if we told you it could be done with two electret microphones, an Arduino, and a Gumstix? Yeah, that’s right. You might want to turn your phone off and sit down for this one.

[Benjamin] and his fellow students developed this brilliant proof of concept design that blocks incoming punches for their final project. We’ve seen boxing robots here before, but this one takes the cake. The details are sparse, but we’ve dug into what was made available to us and have a relatively good idea on how they pulled off this awesome piece of electrical engineering.

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Measuring Magnetic Fields with a Robotic Arm

MagneticArm

Learning how magnets and magnetic fields work is one thing, but actually being able to measure and see a magnetic field is another thing entirely! [Stanley's] latest project uses a magnetometer attached to a robotic arm with 3 degrees of freedom to measure magnetic fields.

Using servos and aluminium mounting hardware purchased from eBay, [Stanley] build a simple robot arm. He then hooked an HMC5883L magnetometer to the robotic arm. [Stanley] used an Atmega32u4 and the LUFA USB library to interface with this sensor since it has a high data rate. For those of you unfamiliar with LUFA, it is a Lightweight USB Framework for AVRs (formerly known as MyUSB). The results were plotted in MATLAB (Octave is free MATLAB alternative), a very powerful mathematical based scripting language. The plots almost perfectly match the field patterns learned in introductory classes on magnetism. Be sure to watching the robot arm take the measurements in the video after the break, it is very cool!

[Stanley] has graciously provided both the AVR code and the MATLAB script for his project at the end of his write-up. It would be very cool to see what other sensors could be used in this fashion! What other natural phenomena would be interesting to map in three dimensions?

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The Amazing Ping-Pong Robot was Fake

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Well — you guys were right. As it turns out, it was actually a pair of animators who fooled the internet.

Not sure what we’re talking about? Last month, the [Kuka Robot Group] put out a highly polished video showing an industrial robot playing table tennis against the apparent world champion of the sport — it was extremely well done and entertaining to watch, but unfortunately… also fake. Weeks after the first [Kuka] video came out, someone named [Ulf Hoffmann] released another video, a small table tennis playing robot that looked almost feasible.

As some of our readers pointed out:

The movements seemed unnatural for the size of the servos and arm structure. ~ James

CGI. As others have pointed out, the shadow of the arm disappears when the robot is show from the side, even though they were added in the other shots. ~ Brandon

My cgi tip off was the cable under the table. It stretches instead of sliding around. ~ Aj

Notice it’s running Outlook Express and Internet Explorer – no self respecting hacker/maker would run those apps – lol. ~ vonskippy

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The Auto Parking Mecanum Robot

mecanum

A while back, Hackaday visited the Clark Magnet School in Glendale, California to sneak a peek on their STEM-focused curriculum, FIRST robotics club, awesome A/V classroom, and a shop that puts most hackerspaces to shame. We saw a few builds while we were there, but [Jack]‘s auto parking mecanum robot was in a class by itself. It deserves its own Hackaday post, and now that [Jack] is on Hackaday Projects, he’s sharing all the details.

The most impressive aspect of [Jack]‘s build is the mecanum wheels; the side plates for the wheels were designed by [Jack] himself and machined on his school’s Haas mill. When the plates came out of the mill they were flat, and each of the fifteen little tabs on the plates needed to be bent at a 45 degree angle. With a CNC jig and a lot of time on his hands, [Jack] bent the tabs for all eight plates.

In addition to the plates, the rollers were custom made from non-expandable polyurethane poured into a CNC milled mold. That’s a one-part mold; [Jack] needed to make sixty of these little parts, one at a time.

The electronics are built around an Arduino Mega communicating with a joystick via an XBee. [Jack] found the relays in the off-the-shelf motor board couldn’t handle the current, so he replaced them with much, much larger ones in a hack job we’d be proud to call our own handiwork. There’s also a little bit of code that allows this motorized cart to pull off the best parallel parking job anyone could ever wish for. You can see that and a few videos of the construction below.

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A Mini Op-Amp Based Line Following Robot

LineRobot

There’s no denying it. Super small robots are just cool. [Pinomelean] has posted an Instructable on how to create a mini line following robot using only analog circuitry. This would make a great demo project to show your friends and family what you’ve been up to.

Analog circuitry can be used instead of a microcontroller for many different applications, and this is one of them. The circuit consists of two op-amps that amplify the output of two phototransistors, which control each motor. This circuit is super simple yet very effective. The mechanical system is also quite cool and well thought out. To keep things simple, the motors drive the wheel treads, rather than directly through an axle. After the build was completed, the device needed to be calibrated by turning potentiometers that control the gain of each op-amp. Once everything is balanced, the robot runs great! See it in action after the break.

While not the smallest line follower we have seen, this robot is quite easy to reproduce. What little robots have you build lately? Send us a tip and let us know!

[via Embedded Lab]

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3 DOF Open Source Robot Arm Is Just the Beginning

Arm3-v1

[Dan Royer] of Marginally Clever had a dream. A dream to build an open-source 6 DOF robot that anyone can make! To do so, he’s been learning robotics for the past two years, and has just finished the first step — he’s designed and built an open source 3 DOF palletizing robot!

He’s based this little guy off of the commercial ABB 460 palletizing robot, which is a tried and true industrial robot. It features all laser cut parts, a few nuts and bolts, some stepper motors and an Arduino UNO for the brain. He’s released all of the design files on Thingiverse and the firmware on GitHub – yet another project we’d like to build if only we had a laser cutter!

And don’t worry, the Arduino UNO is only being used for this first prototype — he’s already started writing code for the RUMBA (Reprap Universal Mega Board with Allegro-driver) controller for revision 2.

Stick around to see it write its first greeting with a marker — Hello World!

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