Robot Clock Writes Time Over and Over and Over

We’ve seen quite a few clocks that write the time out with a pen or marker. If you think about it, this really isn’t a great solution; every whiteboard marker will dry out in a day or two, and even if you’re using a pen, that’s still eventually going to run out of ink.

[ekaggrat] wanted a drawing clock that didn’t have these problems, and after taking a look at a magnetic drawing board, was struck with inspiration. The result is a clock that will perpetually write the time. It’s a revision of one of his earlier builds and looks to be much more reliable and mechanically precise.

A clock that writes time needs some sort of surface that won’t degrade, but can be written to over and over again. Whiteboards and glass won’t work, and neither will anything with ink. The solution to this problem was found in a ‘magnetic writing board’ or a Magna Doodle. These magnetic writing boards have a series of cells encapsulating iron filings. Pass a magnet over one side of the board, and a dot of filings appear. Pass a magnet over the opposite side of the board, and the filings disappear.

[ekaggrat]’s time-writing robot consists of a small Magna Doodle display, a robotic arm controlled by two stepper motors, and two solenoids on the end of the arm. The kinematics come from a helpful chap on the RepRap forums, and with the ATmega644 and two stepper drivers, this clock can write the time by altering the current flowing through two solenoids.

A video is the best way to experience this project, and you can check that out below.

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Hackaday Prize Semifinalist: An Affordable Robotic Arm

Industrial robot arms are curious devices, found everywhere from the back of old engineering classrooms where they taught kinematics in the 90s, to the factory floor where they do the same thing over and over again while contemplating their existence. For his Hackaday Prize entry, [Dan] is building a big robot arm. It’s not big enough to ride on, but it is large enough to automate a few processes in a reasonably well-equipped lab.

This is not a tiny robotic arm powered by 9 gram hobby servos. For the bicep and tricep of [Dan]’s arm, he’s using linear actuators – they’re high precision and powerful. A few months ago, [Dan] tried to design a hypocycloid gear but couldn’t get a $3000 prototype to work. Although the hypocycloid is out, he did manage to build a strange differential pan/roll mechanism for the wrist of the arm. It really is a thing of beauty, and with the engineering [Dan] has put into it, it’s a very useful tool.

If you’d like to meet [Dan]’s robot arm in person, he’ll be at the 2015 NYC Maker Faire this weekend. Check out [Dan]’s Hackaday Prize video for his robot arm below.

The 2015 Hackaday Prize is sponsored by:

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Human Gestures Control this Robot Arm

[Ray Kampmeier] just finished writing some code to allow him to control his robotic arm using force-sensitive hand gestures! He calls it the Robo Marionette.

He’s using a MeArm 4 DOF robotic arm, a Sensel touch interface, an Arduino Uno, and a servo shield for the Arduino to control the MeArm. All the code you need is available on his GitHub, but unfortunately the Sensel touch interface isn’t actually available to the public yet.

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Robot Arm Wields Laser, Cares Not For Your Safety

Here at Hackaday we’ve covered a bunch of DIY laser diode projects. And for good reason, they are just cool. We’ve seen people add lasers to their 3D printers, stick one in a milling machine, use a highly modified scanner and even build a simple XY gantry specifically for the task. To say the least there is definitely a wide range of methods for moving around a laser but we’ve never seen anything like what [Sp4rky] sent in to us. He and his friends outfitted an old educational robot arm with a laser.

The robot arm is a 5 axis Armdroid 5100 picked up from eBay for a couple hundred dollars. It didn’t come with a controller but all of the stepper drivers were housed in the base of the arm. After a little tinkering around with the inputs the team was able to get the arm to move by sending serial commands from a PC, through an Arduino Mega which then sends the appropriate signals to the uni-polar stepper drivers. That was the easy part of the build.

The hard part was getting the arm to hold the laser at a consistent angle and height above the table. Inverse Kinematics to the rescue! Since the desired position of the laser, as well as the length of the arm segments is known, mathematical formulas can be derived to determine the necessary arm segment and joint positions while moving the laser around. The process flow starts out with an image in Inkscape, g-code is then generated with this plugin, then sent to the Arduino running a modified version of GRBL that has the inverse kinematic formulas. The Arduino directly controls the stepper drivers and the robotic arm moves. The Arduino also controls 3 constant-current laser drivers made from LM317 regulators. Three laser drivers, why?

Triple Laser Robot[Sp4rky] got his laser diode modules out of surplus medical equipment and, unfortunately, the rated optical wattage was quite low. Since he had 3 diodes, he decided to try to combine the 3 low power beams into one high power beam. This can be done using a prism. A prism splits sunlight into a rainbow of colors because each wavelength(color) of light that passes through the prism is bent a different amount. Since the laser diodes only put out one wavelength of light, the beam bends but does not split or diffuse. A 3D printed bracket points each laser diode at a 3-sided pyramidal prism which sends the combined beam of light straight out the bottom towards the object to be cut or engraved.

This project is cool enough that we would have covered it even if [Sp4rky] wasn’t burning a Hackaday logo. Although it doesn’t hurt for anyone wanting their project to get covered!

Open-Source Robotic Arm Now Within Reach

For anyone looking for a capable robotic arm for automation of an industrial process, education, or just a giant helping hand for a really big soldering project, most options available can easily break the bank. [Mads Hobye] and the rest of the folks at FabLab RUC have tackled this problem, and have come up with a very capable, inexpensive, and open-source industrial arm robot that can easily be made by anyone.

The robot itself is Arduino-based and has the option to attach any end effector that might be needed for a wide range of processes. The schematics for all of the parts are available on the project site along with all of the Arduino source code. [Mads Hobye] notes that they made this robot during a three-day sprint, so it shouldn’t take very long to get your own up and running. There’s even a virtual robot that can be downloaded and used with the regular robot code, which can be used for testing or for simply getting the feel for the robot without having to build it.

This is a great project, and since it’s open source it will be great for students, small businesses, and hobbyists alike. The option to attach any end effector is also a perk, and we might suggest trying out [Yale]’s tendon-driven robotic hand. Check after the break for a video of this awesome robot in action.

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Hacklet 30 – Robot Arm Projects

Robot arms – they do everything from moving silicon wafers to welding cars. Many a hacker has dreamt of having their own robot arm to serve them beer help them build projects. This week’s Hacklet features some of the best robot arm projects on!

robotarm1We start with [4ndreas] who is building this incredible 3D Printable Robot Arm. Inspired by large industrial robots, [4ndreas] has given us an entirely 3D printable design. [4ndreas’] 3D design experience really shows here. This arm looks like it just finished work at a local assembly line! The arm is BIG too – printing the parts took him about a week, and used around 1.2kg of ABS filament! [4ndreas] has recently split the project off into two halves: his blue arm is driven by stepper motors, while the orange arm is a DC motor affair. Both of the arms can use his awesome gripper design. Check out the project page for videos of the arm in action!

6dofarmNext up is [Dan Royer] and his 6DOF Robot Arm. [Dan’s] didn’t want to spend upwards of $10,000 on an industrial arm, so he built his own from wood, plastic, and easily obtainable parts. As the name implies, the arm has 6 degrees of freedom. The electronics consist of beefy NEMA 17 stepper motors and a RUMBA controller, which was originally designed for 3D printers. Dan even created some novel encoder mounts. Each joint has an encoder, which will allow the robot to run as a closed loop system. [Dan] originally entered this arm in The Hackaday Prize 2014. While it didn’t get him to space, we’re betting it will be able to get him a soda!


No robot arm Hacklet would be complete without featuring [ben.phenoptix] and the awesome MeArm. MeArm is a pocket-sized robot arm which uses tiny 9 gram servos for locomotion. It’s built from laser cut acrylic and standard hardware. We loved the MeArm so much that we featured it as one of the challenges in our Embedded Hardware Workshop in Munich. More recently, [Ben] and MeArm have had a great run on Kickstarter. Let’s hope those arms are good at stuffing, addressing, and mailing out packages!


owiFinally we have [Kenji Larsen] with Reactron material transporter. The material transporter is just a small part of [Kenji’s] larger Reactron project. It started with an OWI-535 robot arm. The OWI is really a toy – a plastic kit which builds an open loop DC motor driven arm. [Kenji] has put some serious time into modifying his particular arm. He experimented with molding his own potentiometers for each joint before settling on a printed circuit board based design. Once the new system was in place, he found that his resistors were good for about 10,000 cycles. Not bad for a modified toy!

There are quite a few robot arm projects we weren’t able to cover in this edition of The Hacklet – you can check them all out on our brand new Robot Arm Projects List!

That’s it for this Hacklet, As always, see you next week. Same hack time, same hack channel, bringing you the best of!