[HN Gopher] Brandon's Semiconductor Simulator
___________________________________________________________________
Brandon's Semiconductor Simulator
Author : dominikh
Score : 178 points
Date : 2025-05-10 00:37 UTC (22 hours ago)
(HTM) web link (brandonli.net)
(TXT) w3m dump (brandonli.net)
| em3rgent0rdr wrote:
| When spice simulation isn't deep enough... Very educational to
| show how circuit elements work "under the hood"...for example the
| LC example doesn't use an L element and a C element as building
| blocks, but rather it is the two metal plates in close contact
| which form the bulk of the circuit's capacitance and it is the
| loop of metal itself which form the inductance.
| amelius wrote:
| I wonder how they simulate EM in only 2 dimensions.
|
| I also wonder why the simulator only allows to show E and D
| fields, and not H and B.
| Steuard wrote:
| I don't pretend to know what this simulation is doing, but
| for the record, electromagnetism works just fine in 2D. You
| might be thinking "but magnetic fields are intimately tied to
| cross products, which only work in three dimensions." But you
| can set up the equations of electromagnetism just fine either
| using differential forms or bivector magnetism
| (https://arxiv.org/abs/2309.02548), and it works in any
| dimension you'd like. (The cross product version is really a
| narrow and sometimes misleading special case.)
|
| Possibly related: there are options to "View B" and "View H"
| in the _scalar_ dropdown, not in the vector one. That may be
| closely related to the fact that in two dimensions, the
| magnetic field has just a single component. Whether you
| describe is as a 2-form or a bivector, the magnetic field is
| an antisymmetric rank-2 tensor: an antisymmetric matrix. In
| 3D, that means 3 independent components, and there 's a one-
| to-one mapping to vectors (more or less). But in 2D, an
| antisymmetric matrix has just one independent component. (And
| in 4D, it's got six: this is precisely the relativistic
| electromagnetic field tensor, that in 3D splits into an
| electric part and a magnetic part. My paper has more
| details.)
| amelius wrote:
| Thanks but I was thinking more about how fields drop off in
| 2D space versus 3D space. Simple electrostatic example:
| consider a 1D string of identical resistors. Voltage drops
| linearly as you go along this string. Now consider a 2D
| grid of resistors: voltage does not change linearly anymore
| if you move between two points (current will move in a more
| complicated spread-out pattern). So the dimensionality
| changes how fields behave.
| ajb wrote:
| That's true, but it's actually a property of the circuit.
| Any circuit that fits into a 2d space will work the same
| if simulated in 3d: voltage will still drop off linearly
| along a 1d resistor.
|
| This is because it's actually an emergent property
| already in 2d space.
|
| Consider a resistor shaped like a capital letter Z in 2d
| space, with ground at one end and 1V the other. (Assume
| also that the Z has a square aspect ratio). The potential
| along the bar in the middle will initially be equal,
| because all points on the bar are equidistant from our
| voltage sources (AKA charges) . But the potential will
| drop along the arms of the Z. So charge will move along
| the arms and accumulate at the corners, until there is
| _also_ a voltage drop along the bar, and ohms law holds.
| stunningllama wrote:
| That's exactly right! In my simulation quantities like E
| and J are vectors with x and y components. In contrast B
| can be thought of as a vector (or bivector, technically)
| pointing in the z direction, but since it it only has one
| component it's simpler to just lump it in with the other
| scalars. (Aside: Having the simulation be in 2D brings in
| some interesting toplogical restrictions on circuits).
|
| - Brandon
| gfody wrote:
| Sebastian Lague has been making one of these and youtubing it,
| the videos are great here's the latest one
| https://www.youtube.com/watch?v=HGkuRp5HfH8
| gblargg wrote:
| Note that these are at very different levels of detail. Lague's
| is at the digital logic level, while Brandon's is some level
| around atoms/electrons.
| petermcneeley wrote:
| Amazing work feels very similar to Paul Falstad page
| https://www.falstad.com/emstatic/index.html.
|
| This really needs a WebGPU port. Multigrid on a GPU is moderately
| easy.
| 1d22a wrote:
| The similarity is likely not a coincidence!
|
| > (c) Brandon Li, 2025. Ported to Javascript with the help of
| Paul Falstad.
| stunningllama wrote:
| Brandon here. I was very much inspired by Falstad's applets.
| I had him take a look at my simulation and he generously
| offered to make a JS port.
| kragen wrote:
| It looks awesome, and I want to express my special
| appreciation that you used red and blue instead of red and
| green.
| mhh__ wrote:
| Really sexy
| paulgerhardt wrote:
| Fun. I am reminded of the long forgotten Zachtronics
| semiconductor game "KOHCTPYKTOP: Engineer of the People" [1]
|
| [1] https://www.zachtronics.com/kohctpyktop-engineer-of-the-
| peop...
| djmips wrote:
| Did you know that archive supports old Flash games like this
| via the Ruffle Flash emulator?
|
| https://web.archive.org/web/20160305205215/http://www.zachtr...
| hteaf wrote:
| cefFlashbrowser can do it better
| ryani wrote:
| This is also available (with an included Flash emulator, so
| playable on modern machines) in Zach's free retrospective
| "Zach-like" [1]
|
| [1] https://store.steampowered.com/app/1098840/ZACHLIKE/
| HKH2 wrote:
| ChipWizard is the updated version and it's in Last Call BBS
| (from Zachtronics).
| spicybright wrote:
| The UI is rough but this is very impressive!
| bdbenton5255 wrote:
| Very clean, educational and informative. Well done, from one
| Brandon to another!
| gitroom wrote:
| im super into stuff like this, takes me back to messing with
| circuit sims for hours
| kragen wrote:
| This looks exciting, but the images make it look like maybe it's
| two-dimensional?
| showmexyz wrote:
| So how accurate are the results?
| westurner wrote:
| Which other simulators show electron charge density and heat
| dissipation?
|
| Can this simulate this?:
|
| "Synaptic and neural behaviours in a standard silicon transistor"
| (2025) https://www.nature.com/articles/s41586-025-08742-4 ..
| https://news.ycombinator.com/item?id=43506198
|
| What about (graphene) superconductors though?
___________________________________________________________________
(page generated 2025-05-10 23:01 UTC)