Bootstrapped Tools, Live Stopped Motion, and a Dekatron Computer

Dallas Texas played host to an epic Hackaday meetup last weekend. The Dallas Makerspace was kind enough to open their doors, and we sure used them. Attendance was over capacity, with a line all night to screen-print your own T-shirt, a set of lightning talks that lasted nearly two hours, and plenty of hardware show-and-tell.

We’ll start off with three of the most impressive builds displayed. First is a set of simple designs that can be used to make tools in parts of the world where even a hammer is a luxury. Then it’s on to a clever entertainment device that uses discrete stopped-motion figurines to make live animations. We’ll take a look at the Witch-E project which is building a replica of the famous Dekatron-based computer. And finish up with the surprise hit of the meetup.

Cool Tools From an Engineer Without Borders

It was a pleasure to meet Larry Bentley, who gave a stellar lightning talk about the tool designs he’s been working on for the developing world.

A lightning talk is only seven minutes, but Larry spent the rest of the night with people crowding around his table to get a look at the very functional tools he built with the most basic of materials. Above you can see him holding a hack saw and a bit brace, both made out of rebar.

Larry is active with Engineers Without Borders, which has taken him to many different parts of the world. For some communities, even a hammer is a tool beyond reach. Check out his toolbox above and you’ll see a stick with a big bolt through it. Financially, this is a more approachable version of a hammer.

So how do you cut the hole in the stick to make your hammer? Larry brought along a DIY drill press he had made. Our fancy electric drill presses spin up to high RPM, but this one uses low RPM and high pressure. A bolt is used to apply leverage to the work piece while the bit is twisted by hand. Check out the close shot on that mechanism. It uses dimpled washers and some ball bearings to create a DIY bearing. And it works well enough to drill through a hardened steel file!

Live Stopped Motion

Live action and stop motion are opposites, right? It’s really hard to catch the effect on camera, but in person this stopped motion animation looks incredible. Colin McGinn built it by mounting figurines on a chain. Each figure is a different frame of the animation, and a synchronized LED works as the “shutter”. I can vouch for him, but if you need more proof, the patent office also thinks he’s onto something: he was just issued a patent.

Colin notes that this isn’t a zoetrope, which traditionally are circular barrels with pictures or models in them. Here’s how he describes the system which is called Tru.D:

Tru.D 3D is a 3D video system. It requires no projection, no optics, and no glasses. Unlike theaters that offer “3D” movies, this is real, true 3D video

This version of the device uses a chain, and Colin’s next iteration will be a system that uses many pulleys to route the chain back and forth. The goal is to get to an animation that lasts about 90 seconds! Can you imagine this scaled up to a theater-size installation? The physics implications of that thought get really interesting.

Witch-E Project is a Dekatron Computer


It was great to run into David Anders who has been featured a ton of times on Hackaday already (here’s an early Linux tablet hack he pulled off). He gave a talk and was showing off the progress of the Witch-E project.

The Harwell Dekatron computer was also known as WITCH. David is part of an effort to recreate the computer as an educational opportunity and they’ve come a long way with it. Of course a project like this can’t depend on having dekatron tubes and all the bits that drive them so Dave has worked up an LED-based stand-in demonstrated below.

The dekatrons are only one piece of the puzzle, though. You also need a punch-tape reader (and writer) to program the original WITCH. For the Witch-E program there is a tape-based reader that uses a computer printer to print the dots on calculator paper, with phototransistors to read back in the data. Who knew modern printers still had banner mode that is used to print on the continuous tape? On the right is a working prototype of the computer which includes a register to take input from the tape reader or switches and push them into the dekatron registers. Keep an eye the front page, Brandon will be posting a full article on Witch-E soon.

Hackaday Dallas

This is such a small part of what went on at the event. Thank you to Brandon Dunson for doing so much planning leading up to the highly successful night. Thank you to Dallas Makerspace for letting us use their meeting rooms. And a big thanks to Supplyframe, Hackaday’s parent company, for providing pizza and beverages for over 100 people, and for underwriting the T-shirt screen-printing.

Speaking of which, Pearce Dunlap led the shirt screen-printing. Look how calm he and Brandon look before the onslaught began. Pearce ended up doing a huge amount of work that night. We had 25 shirts on-hand and had told people to show up early because we’d run out of shirts quickly. And then a ton of people brought their own shirts!

We kept that screen busy long after our supply of shirts was done. I believe we even ended up running out of the white ink purchased for the event. It’s a good problem to have, and a metaphor for the night — so many interesting people, and so many things to do. This was a meetup I’ll remember for a long time to come.

7 thoughts on “Bootstrapped Tools, Live Stopped Motion, and a Dekatron Computer

  1. very cool. When I was doing stop motion for a studio we didn’t like calling it “stop motion”. Think about it, it’s not moving. The models are STOPPED! You are making them move. We called it make motion, but that was the 80’s

    1. I’m not sure which aspect of “Tru.3D” he patented, but the article makes the distinction that his project is not on a spinning “barrel”, so I’m assuming it’s the chain linked frames that’s being considered new. It can’t be the stroboscopic aspect, which every animation of this type uses. A project that would be closer to prior art is the one below, but [Colin McGinn] probably would make the distinction that his isn’t being projected:
      As a person who has been building things like this for decades, and is hoping to continue, it is worrisome that a patent was issued for his project. I’ve been intending to resurrect my battered and broken stroboscopic projects from years past in 3D printed form, but have been distracted by all the other new projects my 3D printer has made possible.

  2. Thermal receipt printers are continuous…
    I am not sure if it is still true, but a dozen years ago, radiosondes included punched paper tapes to load its characteristics before launching. Therefore, punched paper tape readers were still available.

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