DISCLAIMER

This is just for fun, I will rework things but hopefully this is a fun 7 min read. Regardless I think the Veritasium videos on analog computing gave me brainworms. Being surrounded by the charm of digital computers all my life, I can't help feel mystified by these silly guys. Even if these computers never make a comeback, I hope I am able to share the spark I see in them.

What are they?

Analog computers are used for creating an analog of an existing thing. Basically the computer is running a simulation with calculus, although I wont bore you with heavy equations/math, promise! c:

How do they work?

Anything physical that we can trick into doing math, we've made into computers. A electronic voltage, the number of turns on a shaft, the distance of a paper, even hydraulics have been used to represent signals for analog computing. As long as whatever is representing the analog signal can change within a range of two numbers (ex: any number within 10 to -10), it works! Along with being continuous, all math operations are happening at the same time as all other operations of a program. These features make analog computers function very differently from digital computers in terms of use and the components that make them up. Yet, I would like to show that the math operations commonly used are actually deceptively simple. (for clarity I will be assuming you are using an electronic analog computer but other types might apply)

(Setting the X axis to time, the Y axis is the range for the analog signals. Red and Green (if needed) are inputs, and blue is the output.

Coefficient

This math operation takes our input, and multiplies it by a value we set to our output. The set value in this example is .5, but like our signals, this multiplier's value may be anything within a set range.

Adder

Adder: Takes the total value of both (or more!) analog input signals to our output.

Most math operations are pretty self-explanatory. inverters flip positive and negative values. Multipliers multiply analog signals. But, nothing compares to...

✨️Integrators✨️

Integrators are the bread and butter of analog computers! The integrator adds up all inputs over time, and outputs the running total. Think about it like a cup slowly filling up with water, your input is the flow into(or out of) the cup while your output is the fullness of the cup. Before, all you were able to solve were algebra equations. Now you can suddenly do so much more by introducing time into your toolbox.

The easy part

The diagrams for programming analog computers might look daunting, but they're once again, very simple. I'm betting the math operations we went over are going to be most of what you see in programs. The symbology might take a little getting used to, but it really is plug and play!

The hard part

I currently do not know enough about writing programs for analog computers, and hope to someday come back to explain! (spoiler its a lot of differential equations)

That's it for now, I made the graphs in desmos, I heavily used the analog computing wikipedia page and the analog thing documentation as reference/for crosschecking. I also used www.analogmuseum.org for the first 2 refrence images (the first computer shown is a COMDYNA) Also thank you to my friends for crossreading for readability c: wawa