The Power of the Digi-Comp II

Last fall, we built an oversized Digi-Comp II for MIT, which we’ll be posting about in the near future. Today, MIT computer science professor Scott Aaronson published a short “paperlet” about the computational capabilities of the Digi-Comp II on his blog, Shtetl-Optimized:

…it’s amazing that such a simple contraption of balls and toggles could already take us over the threshold of universality.  Universality would immediately explain why the Digi-Comp is capable of multiplication, division, sorting, and so on.  If, on the other hand, we don’t have universality, that too is extremely interesting—for we’d then face the challenge of explaining how the Digi-Comp can do so many things without being universal.

Visited by Toymakers TV

Addie and Whisker of @tymkrs just posted video from their recent epic road trip including a visit to our shop. The video starts off in Colorado and wends through Arizona before getting to the bay area. After stops including the Internet Archive, the Electronics Flea Market and HSC, they arrive to tour our shop (starting at 11:53) before wrapping up at Tindie. We had a great time talking about the Eggbot, WaterColorBot, Digi-Comp II and miscellaneous vintage mechanical and electronic contraptions.

Dr. Nim

Our friend Brian (the designer of the EBB driver board which is used in the Eggbot) recently posted this picture on twitter, with the following caption:

Kids found 1966 ‘computer’ ‘game’ in the closet and LOVE it. Dr. Nim always wins. Our future may be OK.

Dr. NIM was designed by the same engineer, John Godfrey, who designed the Digi-Comp II, and it was manufactured in the mid-1960′s by the same company, E.S.R. Inc. It is even described in the same patent as the Digi-Comp II and works in the same manner, using mechanical flip-flops triggered by marbles. Only, to play the ancient game of Nim instead of doing binary calculations. We were very curious about how Brian came by one, and asked for more information. He wrote what follows:

We were on a week long vacation in Michigan. We rented a large house on the shore of Lake Michigan near Traverse City. The house looked like an extreme example of 1960′s decorating—nothing has been updated since. (Large tables with built-in ash trays, shag carpet, an old radio that had a “magic eye” that lit up when your FM radio station was ‘in hi-fi stereo’, etc.) And, in the closet with the games, was one called Dr. Nim. Us adults never gave it a second glance until one of the older kids noticed that it said “computer” on it, and pulled it out to see if she could get on Facebook with it. My ears perked up, and when I saw the front cover, I couldn’t stop playing with it. Which is not surprising considering my background as an embedded systems engineer. But what I couldn’t believe is that the kids loved it too! We were on vacation with 2 other families, each of which had 3 kids (like ours) of various ages. Very quickly, the 10 year old figured out how to beat Dr. Nim. Of course that made all the other kids want to try. Even the 4 year old learned to play. And then some of the other adults (even non-engineers) tried it for themselves, asking how it could possibly know how many marbles to take each turn so that it would (almost) always win. “How can pieces of plastic be a computer?” they asked. So we had a nice chat about where the term ‘computer’ comes from.

The thing that got me most excited was not that (modern) kids picked it up and were fascinated by it, nor that other adults were intrigued, but the thought that, in 1968 when it was available for sale to the general public, enough normal Americans bought it that it ended up in people’s game closets along with decks of cards and Monopoly. I suppose the thought of owning a ‘computer’ when such things were all the rage, was so new that spending a few dollars on a plastic mechanical game computer was something a lot of people did just out of curiosity.

And the instruction manual! I should have scanned it in. It has a mini-course in binary logic and boolean equations, ending with a discussion on how the game works, and how you can set it up in several different ways to play different games. And then it went on with “does this mean Dr. Nim can think?” and the open ended questions of machine thinking.

Too bad somebody doesn’t make something like that today . . . .  <grin>

After Brian wrote back to us, we found the manual for Dr. Nim through the Friends of Digi-Comp group. (Dr. Nim games frequently come up on eBay as well, if you’re interested in playing with one.)

The manual is truly incredible, with in-depth discussions about not just the mechanism of the game, but commentary on the effect of computing on culture in the long run. We’ll leave you with a thought from the manual, c. 1965:

The strides that man has made in the last 15 years in developing machines that extend and supplement his thinking are truly astounding. Who can say what enormous strides will take place in the next 15 to 30 years?

From the Mailbag: On the Digi-Comp II

dcii_2
Peter wrote in about his experience with the Digi-Comp II:

I just wanted you and the entire Evil Mad Scientist team to know that the Digi-Comp II was a big success.  I used it to explain digital computers to a group of second graders and fifth graders. In an age of iPads and smartphones, it’s surprisingly hard to demonstrate the beauty and magic of digital computer.  The Digi-Comp II was perfect, looked great, and worked flawlessly. Thanks!

Father’s Day Gift Guide

In anticipation of the upcoming father’s day holiday, we’ve put together a little gift guide with selections from our store. We’re also putting all of these items on sale now through June 12: just enter coupon code “VADER” in the shopping cart to receive 10% off.

dcii_2

First up is the Digi-Comp II, First Edition. It’s perfect for teaching the basics of binary math to kids and parents alike.

A5White

The Alpha Clock Five kit, in original Red Edition, the gleaming White Edition, or the brand-new Blue Edition, is the perfect clock for the discerning hobbyist. It’s eminently hackable and full-featured, with digits big enough to see across even the largest of garages or just next to the bed before you put your glasses on.

Diavolino-angle2

For someone expanding their electronic horizons, or working a ton of projects at once, our Diavolino Starter Packs, and AVR Starter Packs will keep them happily busy.

Our Octolively Modules would make an excellent addition to a furniture or remodeling project.

The Art Controller is a modern take on an old classic, perfect for someone with plenty of project ideas who just needs an occasional trigger.

Tools are always a great gift choice, and anyone would be proud to own our ESD-Safe Screwdriver Sets. Another great workbench addition would be our Standard LED Assortment.

Original Egg-Bot with Ostrich Egg-Bot

The Egg-Bot started out as a way for one father used to show his family how cool it could be to play with stepper motors. Both The Original Egg-Bot Kit and the Ostrich Egg-bot are on sale.

The father’s day sale runs through June 12: enter coupon code “VADER” in the shopping cart to receive 10% off these items.

Happy Father’s Day!

The Making of the Digi-Comp II, First Edition

Making Digi-Comp II 1st Edition - 10

We recently announced availability of our “first edition” wooden Digi-Comp II kits.  These are big kits, and there are a variety of different manufacturing steps and processes— from CNC routing to vacuum forming —that have somehow found their way into the build.   In this little photo essay, we’ll show you just what goes into the making of the Digi-Comp II, First Edition.

Continue reading

Digi-Comp II: First Edition

dcii_9

We’re pleased to finally announce availability of our brand new, long-awaited kit, the Digi-Comp II: First Edition. It’s a modern, fully-operational recreation of the original Digi-Comp II— the classic 1960′s educational computer kit —CNC routed from hardwood plywood.

The Digi-Comp II is a binary digital mechanical computer, capable of conducting basic operations like adding, multiplying, subtracting, dividing, counting, and so forth.  These operations are all conducted by the action of balls rolling down a slope, directed by mechanical switches and flip flops, and all powered by gravity.

We’ve been working on project for over two years now, and so we’ve written before, in some detail, about how the Digi-Comp II works, and what kinds of things you can do with it. We’ve written about our larger than life version of the Digi-Comp II, which uses 8 Balls.  We showed off that version at the 2011 and 2012 Bay Area Maker Faires and made a demonstration video to show how it works.   We have also written about our smaller wooden prototypes that we displayed at the 2011 Maker Faire New York.

 

dcii_2

Our new version, the “First Edition,” is a descendent of the latter.  As compared to the “2011″ model, it has a huge number of refinements— including an improved ball feeder that both fits 30 balls at a time (so you don’t need to refill during most calculations) and is jam resistant, a more compact and reliable start lever, better labeling, better flip-flop design, and internal baffles that slow the balls down, to prevent them from flying out of the machine.

 

dcii_10

Many of these improvements were made possible by slightly reducing the size of the balls that we use.  Whereas the “2011″ model used ½” ball bearings, the First Edition uses standard 11 mm pachinko balls, which are easily available, shiny, and rust resistant.  The fact that they are slightly smaller has allowed us to shrink some of the main circuitry, to allow for that larger ball feeder, to use thinner flip flops, and to fit the full machine into the same 10×24″ envelope that we had aimed for, which is considerably more compact than the 14×28.5″ size of the original.

 

dcii_3

One of the nice things about keeping the size under 24 inches long is that we can fit the entire top deck of the Digi-Comp II into our 12×24″ laser engraver— so that we can directly laser engrave markings onto the playfield.  And while it’s nice to be able to write out DIGI-COMP II in huge letters, the more important application is actually adding the individual markings by the flip-flops and registers:

dcii_6

You may notice that the laser marks are very sharp on the “mesas” of the playfield, and less sharp but more bold down below.   This is an intentional effect, created by laser engraving the playfield in a single pass, with the laser focussed just below the level of the “mesas.”  On previous versions, we’ve either lasered the two parts independently, fully in focus at each depth, or focussed the laser halfway between the top and bottom— which leaves the engraving to look uniform, but less sharp, at each depth.   But this method seems to create exactly what we want:  sharp up top where it’s easier to read, and bold down below where it’s harder to see.

 

dcii_5

The playfield itself is made of 1/2″ thick maple-faced veneer-core all-hardwood plywood.  This is a rock-solid material that is about as far from “hardware store” plywood as you can imagine.  We use a CNC router to cut the pivot and limit holes for the flip flops and to carve the channels— roughly 3/8″ deep —where the balls can roll.  The CNC router is precise enough that when we cut the channels for the balls, we evenly split one of the veneer layers, ending up with a clean inner surface.  The Digi-Comp II also has a lower deck, below the playfield, that supports the clear-register and complement functions.  The lower deck is carved in the same way, but does not have any laser engraving.

 

dcii_12

The lower deck is attached below the upper deck by six screws that come down from the top to meet six wing nuts below.  Between the two layers are 3/16″ spacers that keep the decks uniformly separated.  It turns out that it’s actually important to use six screws; our earlier prototypes tended to jam up when the spacing between the two layers wasn’t controlled well enough.

One of the other improvements is that the “First Edition” kit has a very sturdy stand, as shown above.  The laser-cut stand on the “2011″ model was flimsy, and the simple dowels on the original 1960′s kit were not much better.   The new stand is a glued assembly made of two rigid legs and a crossbeam, made of the same remarkably-hard plywood as the rest of the machine.  It can be attached to or detached from the playfield with the two fat thumbscrews.  It holds the playfield at an even 30° from horizontal, such that the top sits about 12 ½ inches above your desk top— a particularly good angle for viewing the playfield.  The stand is actually reversible, so that you turn it the other way and raise the playfield only about 20° from horizontal, giving the option of a slower speed of operation.  If you want to go faster instead, you can overclock the Digi-Comp II by putting a book below the stand to increase the angle.

 
dcii_1

The new ball release mechanism has been fine-tuned and greatly simplified.  We recently showed off a little video demonstrating how this part of the machine works.  The start lever— now nicely labeled —is made of laser-cut poplar, has a brass rivet as its bearing and a glued-in pachinko ball as a counterweight.  When pulled down by a human or a rolling ball, it pushes a stainless steel rod that moves the ball release at the top of the machine to release the next ball.

 

dcii_11

Finally, it’s worth noting that this is called the “Digi-Comp II: First Edition” for a reason: We are planning others.

The original 1960′s Digi-Comp II kit was made of thin vacuum-formed plastic (what we more often refer to as “coffee drink lid material”), supported by a sheet of masonite and fitted with injection-molded flip-flops and switches.  Our CNC-cut wooden versions are much more substantial, but also cost a lot more to make, both in terms of raw materials and fabrication time.  We’ve been slowly working towards what we hope will be a happy medium: a Digi-Comp II made of (more substantial) vacuum-formed plastic, reasonably sturdy, and at a more modest cost.  We still plan to release a version like that, hopefully within the next year.  This has been a long journey for us— making wonderful machines mostly because they are wonderful machines —and we’re very happy to release our first one into the world.

 

The Digi-Comp II: First Edition is now available to order at the Evil Mad Scientist Shop.

Maker Faire is (almost) here!

Digi-Comp II - 02

The 2012 Bay Area Maker Faire will take place May 19 and 20— just 9 days away — in San Mateo, California.
This is the big Maker Faire, and the best. If you’ve never been to Maker Faire, or if you’ve only been to one of the little ones, it’s an experience not to be missed.

Today (Wednesday, May 9) is the last day to buy advance discount tickets for Maker Faire. If you don’t have your tickets yet, this is a great time to get them.

This year we will again be bringing the Giant Digi-Comp II— our supersized binary digital mechanical computer —to Maker Faire. You can read all about the Giant Digi-Comp II here and see a video demonstration of it here. We will also be doing an Egg-Bot demonstration in the Maker Shed.

Finally, we’ll also be participating in Maker Faire Education Day (Thursday, May 17, for K-12 students).

We hope to see you there!

 

Maker Faire NY 2011 and the Digi-Comp II

mfny

Lenore with the Digi-Comp II prototype

We’re here in New York for the 2011 Maker Faire New York (the “World Maker Faire”), held for the second year at the– absolutely fantastic –New York Hall of Science.

This weekend, we’ll be showing off an all-new prototype version of the Digi-Comp II. Back in May, at the Bay Area Maker Faire, we showed off a giant-scale version of the Digi-Comp II, documented here on our blog both in photos and with video.

Our new prototype is at the scale of the original (mid 1960′s) Digi-Comp II, which used half-inch diameter glass marbles. Rather than marbles, we’ve opted for half-inch diameter chrome steel balls–miniature pinballs or overgrown pachinko balls, depending on your perspective. The original machine was made of thin vacuum-formed plastic, supported by a sheet of masonite and fitted with injection-molded flip-flops and switches. While our final version will be fabricated from (very sturdy) vacuum-formed plastic, we’re currently in a phase of functional testing, using CNC-machined wooden versions.

Digi-Comp II (wooden prototype)-- overview

Here is what the whole machine looks like. Despite using the same size ball, the overall size is a bit smaller than the original: 10×24″ versus 14×28.5″. From testing, it’s clear that there are some places that a little more vertical room would make for a more user-friendly design, so it is likely that our final version will be closer to 25-26″ in length.


Digi-Comp II (wooden prototype)-- top section

The top surface of the machine is cut from 1/2″ thick plywood, using a CNC router to make 3/8″ deep channels where the balls can roll. After routing, we added all of the labels by laser engraving. The flip-flops and switches are laser cut from thinner plywood, and rotate on simple plain bearings consisting of 1/16″ diameter stainless steel pins and slightly larger holes drilled through the wood. At the upper right, you can see the ball-release mechanism, which releases a ball when the actuated by the pushrod.

As with our giant model, the design is a functional but not exact replica of the original. All of the flip-flops, registers, and switches are approximately in the original locations, but the “wiring” (really, rolling ball paths) has been created from scratch. One of the non-obvious things when you first look at the Digi-Comp II is that there are actually two levels to the machine. The six “black holes” that you can see above drop the ball down to the lower level, as a shortcut to the bottom or (for certain functions) to flip switches on the top side.


Digi-Comp II (wooden prototype)-- bottom section

On the bottom half of the machine you can see the ball return as the stripy ramp in the center. The stripes on the ramp arise from cutting plywood at an angle (see here for another example). Below that is the Start Lever. When a ball presses down the start lever, it pushes the pushrod that releases the next ball from the top.


We’ll be demonstrating our prototype Digi-Comp II all weekend at Maker Faire. If you’re in the area, please drop come see the Maker Faire, say hi, and try it out!

    Additional resources:
  • If you’d like more information about the Digi-Comp II in general, please take a look at our prior articles (again, with photos and with video).
  • The official site for our project is digicompii.com
  • If you are interested in the forthcoming kit version, please sign up for the Evil Mad Science Mailing List.

A video introduction to the Digi-Comp II

Several weeks ago, we talked about bringing our giant Digi-Comp II to Maker Faire. But now we’re back, and we wanted to show everyone how it works– not just the many folks who came by to see it at Maker Faire.

For those of you just joining us: The Digi-Comp II is a classic 1960′s educational computer kit– an automatic binary digital mechanical computer, capable of conducting basic operations like adding, multiplying, subtracting, dividing, counting, and so forth. These operations are all conducted by the action of marbles rolling down a slope, directed by mechanical switches and flip flops that act as logic gates. Our version is a modern, larger-than life remake. A functional clone, but sized up to use billiard balls instead of small marbles.

(The video is embedded here; if you can’t see it, click through to view it on YouTube.)

Full size

The machine is big at roughly 4×8 feet, and somewhat difficult to video or photograph. To get the overhead view for our video, we ended up moving the machine out to our loading dock and standing above it. The overview shot above required the further assistance of a ladder perched above the edge of the loading dock.

Digi-Comp II - 01

You can find additional photos of our giant Digi-Comp II in this flickr photo set.

See also our prior blog post about this machine, and, of course, digi-compii.com for future updates.