Mechanical Marvel Trades Courage For Chocolate

October 30, 2017 by Steven Dufresne 4 Comments

When we see what [Jason Allemann] does with LEGO, we wonder why more one-offs aren’t made this way. This time he’s made a Halloween mechanical marvel that will surely scare more kids than anything else they’ll encounter on their rounds — so much so that many may even decline the chocolate it dispenses. Who wouldn’t when to get it you have to reach over an animatronic skeleton hand that may grab you while a similarly mechanized spider may lunge onto your hand.

The chocolate dispensing, the hand and the spider are all animated using four motors, a LEGO Mindstorms EV3 brick to control them, and a touch sensor. When a kid presses a pumpkin attached to the touch sensor, the next chocolate candy is lowered by gravity onto a conveyor belt and carried forward to the awaiting child. That much is automatic. At the discretion of [Jason] and his partner [Kristal], using an infrared remote control and sensor, they can activate the skeleton hand and the lunging spider at just the right moment. We’re just not sure who they’ll choose to spare. It is Halloween after all, and being scared is part of the fun, so maybe spare no one? Check out the video below and tell us if you’d prefer just the treat, or both the trick and treat.

We do have to wonder if there’s any project that can’t benefit from LEGO products, even if only at the prototype stage or to help visualize an idea. As a small sample, [Jason]’s also made a remote-controlled monowheel and an actual working printer along with a Morse key telegraph machine to send it something to print.

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Cable Bots, Arise! Domination Of The Universe Is At Hand

October 20, 2017 by John Baichtal 30 Comments

Most CNC robots people see involve belts and rails, gantries, lead screws, linear bearings, and so forth. Those components need a rigid chassis to support them and to keep them from wobbling during fabrication and adding imperfections to the design. As a result, the scale is necessarily small — hobbyist bots max out at cabinet-sized, for the most part. Their rigid axes are often laid out at Cartesian right angles.

One of the exceptions to this common configuration is the delta robot. Deltas might be the flashiest of CNC robots, moving the end effector on three arms that move to position it anywhere in the build envelope. A lot of these robots are super fast and precise when charged with carrying a light load, and they get put to work as pick-and-place machines and that sort of thing. It doesn’t hurt that delta bots are also parallel manipulators, which means that the motors work together to move the end effector, with one motor pulling while the matching motor pulls.

But while Cartesian CNC bots are sturdy workhorses, and deltas are fly-weight racehorces, neither can really cut it when you want to go gigantic. In terms of simplicity and scale, nothing beats cable bots.

Cable Bots

Cable bots use wires or strings pulled by reel-mounted motors, with dimensions limited only by the room to mount the motors and the tensile strength of the cables used. When the strings are tensioned you can get a surprising degree of accuracy. Why not? Are they not computer-controlled motors? As long as your kinematic chain accounts for the end effector’s movement in one direction by unwinding another cable (for instance) you can very accurately control the end effector over a very wide scale.

The following are some fun cable bots that have caught my eye.

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Making Spirographs With LEGO And Math

June 29, 2017 by John Baichtal 11 Comments

Master LEGO builder [Yoshihito Isogawa] has been on a roll lately, cranking out a number of robots that make drawings reminiscent of the classic Spirograph toy. For instance, he built an elegant drawbot out of LEGO elements, seen above. At first glance the monicker “spirograph” seems wrong, because where are the gears? However, [Yoshihito] has them stashed underneath the sheet of paper, with magnets controlling the pens.

His drawbot consists of a platform (cleverly, an inverted LEGO plate) upon which a sheet of paper is laid. One or two pen holders, each with a pair of magnets underneath, rest on the sheet of paper. Beneath the plate, two pairs of spinning magnets rotate around a double layer of 11×11 curved racks, which then play the role of the classic spirograph rings. An EV3-controlled motor powers the whole thing.

He also makes use of an obscure part–the 14-tooth bevel gear, last manufactured by LEGO in 2002 and even then it was mostly sold in part assortments intended for the education market. It’s so obscure LEGO doesn’t even provide the gear in their online building program LEGO Digital Designer, though (of course) the LDraw folks re-created it — it’s brick 4143 in the library, seen below.

Spirograph Gear Math

This gear becomes important in spirograph-style projects because tooth count is everything. There really aren’t that many spirograph designs that can be made with LEGO, because there are a limited number of gears and they mostly have the same tooth counts–the smaller ones sport 8, 12, or 16 teeth, medium-sized ones 20 or 24 teeth, and larger ones 36 or 40 — see a pattern? Such predictability may be great for a building set, but it doesn’t engender a lot of spirograph diversity.

When you compute the number of vertices in a spirograph shape, you take the least common multiple of the two gears (or sets of gears) and divide by the small gear. So a 60-tooth turntable turning a pair of 14-tooth gears has an LCM of 420, and you divide by 28 to get the number of vertices: 15. Remove one of those smaller gears and the vertices increase to 30. The challenge in creating new shapes with a LEGO spirograph lays in swapping in new gears, just like the original toy, and having more ways to come up with unusual gear ratios makes for more interesting drawings.

Another that makes the 14-tooth gear so alluring to [Yoshihito] is that it’s one of the few LEGO gears with a number of teeth not divisible by 4. Among other things this means the gear meshes with an identical gear at 90 degrees. Usually the gears have the same number for each quarter of the circumference and meshing becomes a matter of jogging one gear a scosh. This can be a problem because LEGO axles have a “plus” shaped profile, and you may not want everything on that axle tilted as well — having a 90-degree solution makes a lot of sense.

[Yoshihito] designs LEGO robots out of Isogawa Studio and has written several books on advanced LEGO techniques, published by No Starch. He specializes in small and elegant mechanisms — finding the perfect set of elements that work together effortlessly. You can see an example in the gear assembly to the right — a pair of the aforementioned 14-tooth bevel gears, turned into a normal gear with the help of that golden spacer, none other than a One Ring from LEGO’s Lord of the Rings product line. You can find videos of his projects on YouTube.

[Yoshihito] has released a number of variants of the spirographing drawbot. What’s next? Maybe a harmonograph?

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Make A Plotter Out Of Rulers

June 16, 2017 by John Baichtal 13 Comments

Instructables user [lingib] made a clever and inexpensive pen arm plotter that uses plastic rulers for arms. An inspiring sight for anyone without a bunch of robot parts lying around,

The electronics are straightforward, with an Arduino UNO and a pair of Easy Drivers to control NEMA17 stepper motors connected to robot wheels, which serve as hubs for the rulers. At the end of the arms, an SG90 micro servo raises and lowers the pen as commanded, shoving the whole pen assembly off the paper with its horn—an elegant solution to an age-old drawbot problem. He even wrote wrote a custom Processing program that allows him to control the plotter from his desktop

[lingib]’s experimented with different kinds of drawing machines, including a drum plotter (video after the break), a V-plotter, as well as a rolling drawbot.

You’ll find tons of Hackaday posts about all types of drawing machines, including vintage plotters, plotters for making circuit boards, and even one built out of cardboard.

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These Sands Of Time Literally Keep Time

December 6, 2016 by Steven Dufresne 13 Comments

Hour glasses have long been a way to indicate time with sand, but the one-hour resolution isn’t the best. [Erich] decided he would be do better and made a clock that actually wrote the time in the sand. We’ve seen this before with writing time on a dry erase board with an arm that first erases the previous time and then uses a dry erase marker to write the next time. [Erich]’s also uses an arm to write the time, using the tip of a sea shell, but he erases the time by vibrating the sandbox, something that took much experimentation to get right.

To do the actual vibrating he used a Seeed Studio vibration motor which has a permanent magnet coreless DC motor. Interestingly he first tried with a rectangular sandbox but that resulted in hills and valleys, so he switched to a round one instead. Different frequencies shifted the sand around in different ways, some moving it to the sides and even out of the sandbox, but trial and error uncovered the right frequency, duration, and granular medium. He experimented with different sands, including litter for small animals, and found that a powder sand with small, round grains works best.

Four white LEDs not only add to the nice ambience but make the writing more visible by creating shadows. The shells also cleverly serve double duty, both for appearance and for hiding things. Shells cause the arms to be practically invisible until they move (well worth viewing the video below), but the power switch and two hooks for lifting the clock out of the box are also covered by shells. And best of all, the tip that writes in the sand is a shell. There’s plenty more to admire about the cleverness and workmanship of this one.

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Founding A Company In Shenzhen For Eight Days

November 30, 2016 by Brian Benchoff 17 Comments

Nadya Peek is one of the hackers that should require no introduction for the regular Hackaday reader. She is a postdoc at the Center for Bits and Atoms at the MIT Media Lab. She’s responsible for Popfab, a CNC machine that fits in a suitcase and one of the first implementations of a Core XY stage we’ve seen. Nadya has joined the ranks of Rudolf Diesel, Nikola Tesla, Mikhail Kalashnikov, and George W.G. Ferris by having a very tiny piece of the Novena laptop bear her name. She’s built cardboard CNC machines, and taken the idea of simple, easy to build printers, routers, and drawbots worldwide. She just defended her thesis, the gist of which is, ‘How to rapidly prototype rapid prototyping machines.’ She’s also one of this year’s Hackaday Prize judges, for which we have the utmost appreciation.

This year, the organizers of the Fab 12 conference on digital fabrication in Shenzhen turned to Nadya and her team to bring their amazing experience to conference attendees. A workshop was in order, but Nadya didn’t have time to organize the logistics. The conference organizers made a deal: the Center for Bits and Atoms would teach a workshop, but getting all the materials and electronics was the responsibility of the organizers.

Upon arriving at the Shenzhen Sheridan, Nadya found the organizers didn’t hold up their end of the bargain. The cardboard, motors, electronics, and glue were nowhere to be found. A “rider” doesn’t quite translate from English, it seems. This is Shenzhen, though, where you can buy all the cardboard, motors, electronics, and iPhone clones you could imagine. What was the solution to this problem? Founding a company in Shenzhen for eight days.

Half a tourist’s guide to Shenzhen and half a deconstruction of what goes into cardboard CNC, Nadya’s talk for the 2016 Hackaday SuperConference covers what happens when you have a week to build a company that will build machines that build machines.

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Sandy Poems Drawn By A Robot Named Skryf

October 15, 2015 by James Hobson 14 Comments

If you were lucky at the 2015 World Maker Faire you may have stumbled upon strange writings of poetry on the ground — written in sand. While at first confusing, if you followed the poetry along you also caught a glimpse of Skryf, a draw bot by [Gijs van Bon].

The creator was asked to perform poems for a festival about transition and letting go. Naturally, building a robot to write poetry in sand was the downright obvious answer to the question.

I was asked to perform 40 poems during a 10 day festival, and the poems were about transition and letting go. And then I thought the obvious thing to do as an artist is to make a machine that writes those poems with sand. I started writing them, and when the third poem was written, the first one was completely gone, and it was such a beautiful thing.

The robot uses a laptop for input, which is connected to the bicycle carriage. One servo controls the left-to-right movement, and another releases the sand. Forward and back is controlled by the main drive train, which must have been fun to account for (they aren’t servos!)

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