LEGO DigiComp II

A LEGO version of an old "marble logic" computer called Digi-Comp II. I set out to rebuild it from LEGO, using various tidbits and plans from the internet. More pictures of the components can be found in my Brickshelf gallery here:

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=288822

I tried to recreate the original DGII design, but did make a few modifications, such as changing the "clear" switch to "clear once" style operation, & not bothering with the "auto/manual" switch (defaults to automatic) or neatly routing all the outputs back to a single collection tray (in particular, the "M/Q underflow"). It works amazingly well, and I think could be modified to essentially release four balls closely spaced in multiple mode.

I owe a debt of gratitude to the "Friends of Digi-comp" Yahoo group for advice & documentation, & to ESR & John Godfrey for making such an ingenious mechanical computer in the first place.

The finished model weighs about 10 pounds, & uses 14 simple switches, 21 flip-flops, 8 half flip-flops, and a ball release mechanism. I'm currently building a slightly improved copy at the request of a museum, for public display.

Category:

Howto & Style

Tags:

• DigiComp
• DCII
• GBC
• LEGO
• Rolling
• ball
• sculpture
• RBS
• marble
• logic
• computer
• binary
• technology

[NorthCountryTech]

Impressive. If you get bored again it might be interesting to think up a design for a memory bank and an instruction queue of some kind and make it into a programmable machine. :)

[brdavis5]

@NorthCountryTech It would be nice :). A significant problem is that balls only roll downhill... so setting up any system where things can feed back is difficult. Here, it's done with a large lever arm and a very long carefully adjusted string. That's tricky if you need to communicate a complex state back to the top.

[ariw2003net]

What museum? There's something that looks exactly like this at the System Source computer museum in Hunt Valley, MD. Or did they just build one based on your design?

[brdavis5]

@ariw2003net Actually, that's the one :). They asked me to build them a copy, so I did (with a few additional things like routing for the overflow balls). Glad to hear it's still on display.

[ariw2003net]

@brdavis5 Haha, that's a funny coincidence. I was just looking for mechanical logic gates/computers on the Internet and found this. I guess not too many people build this sort of thing. Awesome job, by the way, I have seen a live demonstration of this and it's really cool. Sometimes when I go to System Source, it's not really in a working state, but Bob usually fixes it sooner or later (he's my uncle).

[brdavis5]

@ariw2003net That is fantastic to hear! I'm glad you find it fun... and I find it FANTASTIC that it's still operational and (being made of LEGO) can be fixed and maintained fairly easily.

[disneya380]

we should all use this instead of windows

[Lewis1711]

Does anyone know where I can find a C compiler for this architecture???

[bulacha007]

damn finally the world makes sense !

[doldiz1]

I played Half-Life on it!

[GrizzlyRecoveryZone1]

so basically we're smartly manipulating the flow of energy to solve complex mathematical problems? Oh, so that's what computers are!

[legoclockfreak710]

@disneya380 at least you wouldnt get the blue screen of death