Domino logic

September 1, 2008 10:46 PM

Neil Fraser builds logic gates out of dominoes. (See also this half-adder.) Via Mathpuzzle.
posted by Upton O'Good (18 comments total)

Pretty cool. Although rebuilding that XOR gate over and over must get pretty boring.
posted by grouse at 11:08 PM on September 1, 2008

To really make a complete computer, I’d need a NOT gate, which sadly is pretty complicated with dominos - I figure you’d need a clock and a mechanism to stand dominoes back up again - I’m imagining a piece of string tied to the pendulum of a grandfather clock, something like that anyway…

He already has an XOR gate. A XOR 1 = !A.
posted by delmoi at 11:18 PM on September 1, 2008

check out the rest of his pages.

the in-memory JS bmp generator was interesting.
posted by troy at 11:43 PM on September 1, 2008 [1 favorite]

And as kind of the converse, you can use computer technology as dominoes...One Thousand Five Hundred Dead Hard Drives!
posted by Kronos_to_Earth at 12:01 AM on September 2, 2008 [2 favorites]

I think the objection to using XOR for NOT is that you would have to inject 1s at just the right time for each NOT operation. This is similar to the complaints about using a sync signal. Perhaps a simpler solution might be to use two parallel lines, where the left line toppling is 0 and the right line is 1. NOT is then a simple cross-over. AND is a bit trickier, see here for my sharpie sketch. If you buy it (I don't have any dominoes handy), those two gates should be sufficient, with no need for injections.
posted by chortly at 1:42 AM on September 2, 2008 [1 favorite]

At current toy prices I believe it's still cheaper to build a computer out of Tinkertoys or water.
posted by twoleftfeet at 3:29 AM on September 2, 2008 [1 favorite]

Just a half-adder? Pshaw.

I once saw a guy use dominos to make a whole Python.
posted by orthogonality at 4:17 AM on September 2, 2008 [1 favorite]

thought this was really boring when i first saw it - and somewhat obvious.
posted by mary8nne at 4:22 AM on September 2, 2008

Is a planar circuit Turing equivalent? Otoh, dominos are nor planar since you can build bridges.
posted by jeffburdges at 4:42 AM on September 2, 2008

Watching someone stand up dominoes for three and a half minutes -- even in fast forward -- makes me want to break things.
posted by [NOT HERMITOSIS-IST] at 7:47 AM on September 2, 2008 [1 favorite]

Ha! That's great. It's not turing-machine-in-Conway's-Life, but it's nice.
posted by cortex at 7:56 AM on September 2, 2008

Kronos_to_Earth> you can use computer technology as dominoes...One Thousand Five Hundred Dead Hard Drives!

What a gratifying thlunking noise they make.
posted by adamt at 8:43 AM on September 2, 2008

Very nice. But wasn't the AND gate a bit off, in that the domino pattern required him to trigger the inputs in a particular order to get the result?
posted by Durn Bronzefist at 9:36 AM on September 2, 2008

No, the AND gate was fine; he just didn't demonstrate both orderings. I think he showed only the less obvious successful ANDing to save time. I noticed it too, for what that's worth, but I worked it out that the alternate order should easily succeed as well (take down the blocker ahead of time and the faller will fall just fine).
posted by cortex at 9:40 AM on September 2, 2008

Re-watched. Yep, I think you're right. The step ladder will let let the right column bypass the fallen left column, no problem.
posted by Durn Bronzefist at 10:42 AM on September 2, 2008

I like how it looks like I'm all flipping out there a little bit. Like AND ANOTHER THING.
posted by cortex at 10:44 AM on September 2, 2008

Turing machine in Conway's Life.
posted by Upton O'Good at 11:03 AM on September 2, 2008 [1 favorite]

I'm sure someone must've linked to this Lego Turing machine before, but I can't find it on Mefi.
posted by GeckoDundee at 6:04 AM on September 3, 2008