←back to thread

The Analog Thing: Analog Computing for the Future

(the-analog-thing.org)
108 points cgeier | 2 comments | 19 Nov 24 17:09 UTC | HN request time: 0.001s | source
Show context
Ductapemaster ◴[19 Nov 24 18:36 UTC] No.42186703[source]▶
In my upper-division analog electronics class (the hard one), our lab project throughout the quarter was to build an analog computer that simulated the physics of a bouncing ball. Physical variables of the system were adjustable (gravity constant, coefficient of restitution, etc), and the ball was "released" by pressing a button. The output was viewed on an oscilloscope.

One of the hardest 10 weeks of my life, but also one of the most rewarding. Our team was one of the few that actually got it working in the end. I had to custom-make a gigantic breadboard to hold the entire circuit.

Today I still work in hardware, but mostly with digital circuits. While my analog knowledge has decayed over the last decade, that project and it's success gives me great confidence any time I have to deal with the domain.

If you want to take a look, here's a pretty similar project: https://www.analogmuseum.org/english/examples/bouncing_ball_...

replies(4): >>42186864 #>>42188122 #>>42188230 #>>42189794 #
1. klysm ◴[19 Nov 24 18:53 UTC] No.42186864[source]▶
Did the mathematical model being used have a differentiable heigh function? I’m imagining it would be the simplest if it didn’t but that could cause problems in the electronics.

Also what components did you have access to, just op amps?

replies(1): >>42187017 #
2. Ductapemaster ◴[19 Nov 24 19:13 UTC] No.42187017[source]▶
Just op-amps and FETs for the active components. The design from my memory was:

- To get position, 2 integrators were applied to an adjustable voltage representing gravity.

- The FETs were used to set initial states of the integrators.

- A comparator used to detect the table (y=0), flip the velocity and apply a scaling factor for restitution

The math was actually quite simple given its just the standard velocity equations — the challenge was in handling state changes in the electronics.

I looked around a little more and this video is a very close replica of what we built: https://www.youtube.com/watch?v=qt6RVrmvh-o