Two-Stage Tentacle Mechanisms Part II: The Cable Controller

A few weeks back, we got a taste for two-stage tentacle mechanisms. It’s a look at how to make a seemily complicated mechanism a lot less mysterious. This week, we’ll take a close look at one (of many) methods for puppeteering these beasts by hand. Best of all, it’s a method you can assemble at home!

Without a control scheme, our homebrew tentacle can only “squirm around” about as much as an overcooked noodle. It’s pretty useless without some sort of control mechanism to keep all the cables in check at proper tension. Since the tentacle’s motion is driven by nothing more than four cable pairs, it’s not too difficult to start imagining a few hobby servos and pulleys doing the job. To get us started, though, I’ve opted for hand controllers just like the puppeteers of the film industry.

Enter Manual Control

Hand controllers? Of all the possibilities offered by electronics, why select such an electronics-devoid caveman approach? Fear not. Hand controllers offer us a unique set of opportunities that aren’t easy to achieve with most alternatives.

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The Bootup Guide To Homebrew Two-Stage Tentacle Mechanisms

What’s not to love about animatronics? Just peel back any puppet’s silicone skin to uncover a cluster of mechatronic wizardry that gives it a life on the big screen. I’ve been hunting online for a good intro to these beasts, but I’ve only turned up one detailed resource–albeit a pretty good one–from the Stan Winston Tutorials series. Only 30 seconds into the intro video, I could feel those tentacles waking up my lowest and most gutteral urge to create physical things. Like it or not, I was hooked; I just had to build one… or a few. This is how you built a very real animatronic tentacle.

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I built this. And you can too!

If you’re getting started in this realm, I’ll be honest: the Stan Winston Tutorial is actually a great place to start. In about two hours, instructor Richard Landon covers the mindset, the set of go-to components, and the techniques for fabricating a tentacle mechanism with a set of garage tools–not to mention giving us tons of real-film examples along the way [1].

We also get a sneak peek into how we might build more complicated devices from the same basic techniques.  I’d like to pick up exactly where he left off: 4-way two-stage tentacles. And, of course, if you’ve picked up on just how much I like a certain laser-cuttable plastic at this point, I’m going to put a modern twist on Landon’s design. These design tweaks should enable you to build your own tentacle and controller with nothing more but a few off-the-shelf parts, some Delrin, and a laser cutter… Ok, fine, a couple 3D printed parts managed to creep their way in too.

bom_graphicIn a good-ol’ engineers-for-engineers fashion, I’m doing something a little different for this post: I’m finishing off this series with a set of assembly videos, a BOM, and the original CAD files to make that beast on the front page come to life. As for why, I figured: why not? Even though these mechanisms have lived in the robotics community and film industry for years, they’re still lacking the treatment of a solid, open design. This is my first shot at closing that gap. Get yourself a cup of coffee. I’m about to give you every bleeding detail on the-how-and-why behind these beasts.

All right; let’s get started.

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Arduino Powered Knife-Wielding Tentacle Will Leave You In Stitches

Writing articles for Hackaday, we see funny projects, and we see dangerous projects. It’s rare to find a project which combines the two. This one somehow manages to pull it off. [Outaspaceman] is familiar with LittleBits, but he’s just starting to learn Arduino programming. He completed the blink tutorial, but blinking an LED just wasn’t enough fanfare for the success of his first Arduino program. He connected the Arduino Mega’s LED output to a pair of LittleBits which then switch a servo between two positions. A bare servo wouldn’t be much fun, so [Outaspaceman] connected a tentacle and a small Swiss army knife. Yes, a knife.

The tentacle in question is designed to be a finger puppet. There’s something about a tentacle waving a knife around that is so hilarious and absurd that we couldn’t help but laugh. We’re not alone apparently, as this video has gone viral with over 1 million views. It’s almost like a violent revenge of the most useless machine. For the technically curious, the tentacle’s seemingly random motion is analogous to that of the double pendulum.

Our readers will be happy to know that [Outaspaceman] has made it to the Arduino servo tutorial, and is now controlling the servo directly, no LittleBits needed. We just hope he has a good way to turn his creation off – without the need for stitches.

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Printed Tentacles For PCB Probing

Every hacker workbench has one or more of those “helping hand” devices to aid in soldering and assembly. When it comes to testing and debugging though, it could get tricky if you have to start handling test probes while looking at the meter display or fiddling with knobs on the oscilloscope. Sometimes one has to test a board that has just pads for test points. Or maybe you need to directly probe pins on an IC. Checking multiple signals on I2C, SPI, Serial or USB is not too easy with just two hands. [Giuseppe Finizia] is an electronic engineer at the Scientific Investigations Department of the Carabinieri in Italy. He works as a senior analyst in the Electronic Forensics Unit and deal’s with technical investigations on seized electronic devices. To help him in his investigative work, he designed and built a 3D printed PCB workstation with octopus-like tentacles that provides all the additional fingers needed.

The tool is basically a base with adjustable clamps where the test PCB can be fixed. Around the base, up to twelve articulated “tentacles” can be fixed. Various test accessories are attached to the ends of these tentacles – Alligator Clips for holding electronic parts, IC Hook Clip Grabbers, Micro SMD Grabber Test Clips and some others that he is still working on. [Giuseppe] used  MOI 3D modeling software to design his device, and the files are available on Thingiverse for download. He does warn that printing all the parts, specially the tentacle units, can be quite tricky on a regular 3D printer. He used a ZORTRAX M200 printer in high resolution mode and Z-HIPS filament. However, it may be easier to just use machine shop flexible coolant pipe for the tentacles. This may require some sort of modification to the base mounts and the business end of the tentacles though.

Thanks to [CFTechno] for sending in this tip.

Robotic Tentacles For A Disturbing Haunted House

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[ivorjawa] is putting on a haunted house this Halloween that we really don’t want to go to. His robot tentacle is already supremely creepy, and we’re assuming it will only be more frightening once it’s covered in fabric and foam rubber.

Each tentacle can move on two axes thanks to four steel cables running through this strange Geiger-esque contraption. In the base of the tentacle are two stepper-motor driven cylinders that take up slack on one cable and draw out another cable. Two of these control boxes, driven by a stepper motor and an Arduino motor shield, allow the tentacle to reach out and grab in any direction. You can check out the mechanics of the build on [ivorjava]’s flickr

On a semi-related note, even though we’re more than a month out from Halloween, we should have more Halloween builds in our tip line by now. If you’re working on one, don’t be afraid to send it in, even if you’re just showing off a work in progress.

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Tentacles And Phalanges Made From Drinking Straws

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He human hand is one of the most impressive pieces of machinery – biological, mechanical, or otherwise – that you’ll ever lay eyes on.  With two dozen degrees of freedom, the hand can gently caress the most fragile flower petal without bruising it, or beat a hammer into an anvil with tremendous force. Simulating the human hand, however, is quite a challenge that requires dozens of servos and complex mechanical linkages. [Tomdf] over on Instructables is able to create hands, tentacles, and other weird biological contraptions using spring-loaded drinking straws and custom-made 3d printed joints.

[Tomdf] got the idea for drinking straw phalanges after seeing a few 3D printed drinking straw connectors meant to be used for creating 3D objects out of disposable plastic tubes. After designing a new spring-loaded joint for drinking straws, [Tomdf] is able to add a few lengths of thread to serve as ligaments to control the segments of drinking straws. It’s a similar setup to the horrible demon spawn we saw at Maker Faire last year, but far more extendable for any project that might pop into your head.

You can check out the drinking straw tentacles in action after the break.

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Learn About Robot Arms By Building Pedro 2.0

Whether you’re a kid or a kid at heart, learning about science and engineering can be a lot more fun if it’s practical. You could sit around learning about motors and control theory, or you could build a robot arm and play with it. If the latter sounds like your bag of hammers, you might like Pedro 2.0.

Pedro 2.0 is a simple 3D-printable robot arm intended for STEAM education. If you’re new to that acronym, it basically refers to the combination of artistic skills with education around science, technology, engineering and mathematics.

The build relies on components that are readily available pretty much around the world—SG90 servo motors, ball bearings, and an Arduino running the show. There’s also an NRF24L01 module for wireless remote control. All the rest of the major mechanical parts can be whipped up on a 3D printer, and you don’t need a particularly special one, either. Any old FDM machine should do the job just fine if it’s calibrated properly.

If you fancy dipping your toes in the world of robot arms, this is a really easy starting point that will teach you a lot along the way. From there, you can delve into more advanced designs, or even consider constructing your own tentacles. The world really is your octopus oyster.