Glen Anderson’s created an analog computer that uses water to demonstrate digital logic
A computer that uses water instead of electricity? That’s what Glen Anderson and his daughter, Dale, are demonstrating at Maker Faire Bay Area this weekend. He invites kids to fill buckets and dump them into one of four water tanks. On Friday, I asked him how it was going. “I am adding 1 and 1 but getting 1,” he said. Something was wrong and he was working to fix it.
Glen said his goal for the project was to demystify how computers “think”.
Glen showed off his project at Maker Faire in 2019 and he’s back this year with a set of posters explaining how they work.
I asked David to tell us about himself and his project.
I was a CPU designer in the 1990’s in Silicon Valley. I bragged to my 4 young girls at the time that I would be famous someday for the water computer that I tinkered with on and off during their childhood, thus the tongue-in-cheek name. I worked on cool things like a hardware divider and square root!
I’m a EE from Berkeley, and there’s long been this analogy of height of water meaning voltage for analog circuits, you can model a lot with high fidelity including capacitance and inductance etc, even AC effects. I always thought there should be a digital version of this analogy showing how neat it is to perform digital logic when all you have to work with is this magic 3-terminal device called a transistor (or vacuum tube before that). I wanted to demystify how computers work. I mean, it’s complicated but also understandable.
The key is this ping pong ball that floats in a “high voltage” (water pressure) and controls a gate flap o-ring thing that connects source to drain or not. This is like the “semi” in semi-conductor. The channel in a transistor conducts only when there is a voltage present at the gate terminal. Same for my water transistor.
So then I use that to build a 4-bit adder using standard logic techniques with a NOT and NOR gate. It uses 65 transistors total to add two 4-bit numbers such as 9+12.
Different ages react differently. Little kids just like to play with the water and tubes, and as they get older they will figure out the NOR (NOT_OR) logic of the gate by trying inputs. And then some try to understand the whole adder, more complex functions like the XOR function needed to produce the sum bit. In 2019 we had some kids hang with me all day just because they were attracted to the mechanism and helped me with the water pumping which I’ve kept manual on purpose to make the exhibit interactive (and fun–no pump and electricity needed)
There are a few water logic demonstrations on the web (youtube) that are neat, but a fundamental difference is mine are powered gates like in a real computer. The water doesn’t just flow from up high and flow all the way down using the signal itself which degrades. So my architecture is scalable and you can do things like perform memory functions (flip flops and latches). I even filed a provisional patent and let it expire on purpose just to put this invention in the public domain. I’ve thought of making it a product toy but that’s a lot to take on. I think this thing is unique in the world!
Come see Anderson’s Famojus Water Computer at Maker Faire Bay Area on Mare Island.
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