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Comment by usrusr | Hacker News Reader

Oh, it's an analog computer. I was hoping for water-driven logical gates. I think those could be awesome as interactive urban decoration installations. Perhaps a three bit adder in the park that you can also dip your feet in on a hot summer day, disturbing the calculation currently keyed in at the top. Why is that not a thing!

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I think it's a really cool idea. How To Invent Everything (by Ryan North) describes a water logic gate that works as either AND or XOR gate depending on which drain you look at.

I have my doubts about pulling it off as he describes, though. It depends on two streams of water flowing out of angled pipes such that such that when they both flow, they collide and combine into one stream falling straight down. That seems pretty finicky to get right.

Edit: Someone did it! The AND gate worked great, the XOR not so much. So they made it out of greedy siphons instead: https://www.youtube.com/watch?v=IxXaizglscw

Nice, can we call those solid state? I was thinking more along the lines of sluice gates mechanically operated by floats.

I have for years wanted to build a digital clock using water. I believe fluid gates and transistors are a thing, but they probably depend on a substantial flow/current, and I imagine they'd be hard to miniaturize. So you'd need a big header tank (corresponding to a high Vcc).

The display I envisaged would be a seven-segment dispay, made simply by pushing a dyed immiscible liquid in and out of transparent tubes in the display window.

I expect it would be messy; imagine waking up to the morning alarm, reaching for the snooze button, and getting a bucketful of cold water tipped over your head.

IN the 60s and 70s there were ideas of using actual ponds as computers

Because you haven’t made it a thing yet ;) But you absolutely should.

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