LEGO logic gates: a reliable binary adder

Serendipitously, I discovered a novel LEGO machine designed by Hiro Labo, a professor at a university in Osaka, Japan. This conceptually simple machine reliably performs binary addition on two single-bit numbers, without the excessive joint play and gear backlash I’ve experienced in other designs. Naturally, I had to replicate it: the plates on the left stack to form the adder on the right.

A day off from the world

It was a day for isolating ourselves from the world: the weather was still too frigid to go outside, plus we declared a no-news day. I prototyped a LEGO pneumatic AND gate that functions significantly better than the gates I built yesterday. However, I won’t be building a pneumatic adder any time soon because I don’t have enough pistons.

Stalled by joint play in a LEGO mechanical computer

All logic functions can be constructed using AND and NOT logic gates. Modern smartphones contain billions of logic gates. However, the LEGO machine I constructed today only has four AND and four NOT gates to perform binary addition on two single-bit binary numbers. As the signal propagates from the inputs on the left to the outputs on the right, the cumulative effect of joint play leads to unreliable output movements. I need to redesign the machine.