robryk @robryk@qoto.org
I enjoy things around information theory (and data compression), complexity theory (and cryptography), read hard scifi, currently work on weird ML (we'll see how it goes), am somewhat literal minded and have approximate knowledge of random things. I like when statements have truth values, and when things can be described simply (which is not exactly the same as shortly) and yet have interesting properties.
I live in the largest city of Switzerland (and yet have cow and sheep pastures and a swimmable lake within a few hundred meters of my place :)). I speak Polish, English, German, and can understand simple Swiss German and French.
If in doubt, please err on the side of being direct with me. I very much appreciate when people tell me that I'm being inaccurate. I think that satisfying people's curiosity is the most important thing I could be doing (and usually enjoy doing it). I am normally terse in my writing and would appreciate requests to verbosify.
I appreciate it if my grammar or style is corrected (in any of the languages I use here).
Joined Nov 2020
@delroth While experimenting with self-hosting be aware that the state machine for following has no support for reconciliation (so if you mess up the state on your side, it might stay inconsistent forever without anyone noticing).
Things that are very weirdly broken in a nearly-necessary way: https://bugs.busybox.net/show_bug.cgi?id=15101
https://www.msri.org/people/staff/levy/files/MCL/Zvonkin.pdf
This is a:
a) tale of trying to teach young (preschool) kids actual mathematics (not counting),
b) description of an approach to that
c) book that contains problems that are simply stated and sometimes nontrivial (in particular games, where the winning strategy is very unobvious).
robryk
boosted
Another standard electronics practice is slapping a cheap and huge electrolytic capacitor on the DC power line, even in low-power devices. Clueless audiophiles would tell you it's like a pool of water that buffers energy to smooth the voltage. Until you realize their high series resistance and inductance make them useless at > 1 MHz in modern electronics, and often makes no sense.
What's the true reason? Resonance damping and control-loop stability. The inductor and capacitor are the input of a PSU form an LC resonator. At its natural frequency, noise voltage is not filtered but is significantly increased, ringing like a bell. Also, a regulated power supply has negative resistance, resonance turns a power supply into an oscillator.
A cheap and huge capacitor has high series resistance, it works as friction to dissipate energy, making it unable to ring. The capacitance also needs to be huge, since resonance occurs at a low frequency, the AC reactance must be low. For bonus, you get DC energy storage as explained by "conventional wisdom". All from a cheap low-quality capacitor... "It's not a bug, it's a feature!" #electronics
I am once again slightly-amusedly-enamored by Freefall:
http://freefall.purrsia.com/ff3900/fc03821.png
Helix: How was my story telling?
Sam: Not bad. You'll get better with practice.
Sam: Storytelling is an art that comes naturally to humans and sqids. It starts almost as soon as we can form sentences.
Dialog: My dolly wanted a cookie.
Sam: Robots see the world as it is and naturally tell the truth. It's a bad habit and with my help, one you'll learn to overcome.
robryk
boosted
"it should be about as labor-intensive to wire wrap through-hole components as it is to solder them"
Mass production uses wave soldering. You simply insert all the parts into the board, soak the board into molten solder, and pull it out. bingo, the full board is soldered within seconds. You can't wrap all the wires within seconds."due to wire shape, unwanted capacitances are kept much smaller in wire wrap (compared to e.g. a 2-layer PCB),"
Due to physical construction, unwanted inductances are much higher compared to a PCB. Even for advanced wire-wrap boards with ground planes (people used them in the late 80s during wirewrap's last days), it's still difficult to match a PCB's performance. A typical 4-layer board's signal layer is 0.1 mm above the ground plane, a wire-wrap board it's typically 5 mm, causing a 40x increase of loop area."no need for explicitly making multi-layer PCBs: the problems of routing, possibly stacking layers (for >2 layer ones), coating vias, etc. just go away."
One huge motivation to use a multi-layer PCB in modern designs is not even extra layers for the signals, but to have solid power and ground planes that contain nothing but solid copper. A copper pour on a multi-layer PCB naturally forms microstrips, the simplest kind of microwave transmission line, which is required to support high-speed digital signal transmission. Likewise, the capacitance between the signal layer and a ground plane is a feature, not a bug. Because of its planar circuit nature of a PCB, characteristic impedance is tightly controlled and extremely reproducible. Overlapping wires over a ground plane do not have a consistent characteristic impedance.Even in lumped circuits and analog designs when controlled impedance does not matter, a solid ground plane is often still important to minimize loop area and parasitic inductance. Modern power MOSFET's switching speed is reaching 100 volts per nanosecond.
Standard wire-wrap construction is ill-suited above 10 MHz. Even back in the late 80s when electronics is made of really slow through-hole parts by modern standard, wire-wrap already started to show serious signal integrity problems.
---
But... Believe it or not. All of these problems I listed have been solved already in the 80s by combining the best of both world. The final next-gen invention was called "Multi-Wire" circuit board. It looks like a normal PCB but its inner layer uses insulated wires for connections, allowing overlapping traces. The ground planes and outer layers are similar to PCB. Reportedly,
IT can convert a multi-layer PCB design with 12 signal layers to a six-layer board with just two signal (wiring) layers.
But it was an highly expensive technology, and did not see much uses outside niche high-end applications. Today Hitachi is one of the few companies that still offer this service.https://www.swtest.org/swtw_library/2013proc/PDF/SWTW13-22.pdf
I still get amused once in a while by the combination of pomp and absurdly detailed requirements in the Swiss constitution:
"Im Namen Gottes des Allmächtigen!
Das Schweizervolk und die Kantone,
in der Verantwortung gegenüber der Schöpfung,
(...)
gewiss, dass frei nur ist, wer seine Freiheit gebraucht, und dass die Stärke des Volkes sich misst am Wohl der Schwachen,
geben sich folgende Verfassung:
(......)
Der Anteil von Zweitwohnungen am Gesamtbestand der Wohneinheiten und der für Wohnzwecke genutzten Bruttogeschossfläche einer Gemeinde ist auf höchstens 20 Prozent beschränkt.
(...)"
Wow, https://gcn.gsfc.nasa.gov/other/221009A.gcn3 was a Gamma Ray Burst that caused noticeable disturbance of ionosphere.
...
"Both. You learn that it's not about recipes at all."
"So, you do anything you want with magic?"
"Well, not just by wishing it. When you learn how to think about magic, you learn how to predict its effects."
"...and then I can try to figure out what to do so that I would have the effect I want?"
"Yes. Just like when you deal with any other part of the world."
Pratchett's #dragons are to all dragons just like gnomes are to people in standard fantasy settings. (They all are tinkerers, though out of necessity~.)
2685. 2045
"I have another appointment that would be really hard to move, in terms of the kinetic energy requirements" is my favourite phrase of the week
robryk
boosted
Frist psot!
I today realized (yet another) reason why one must slowly start steam boilers: steam flow provides cooling of e.g. superheaters. Thus, if the heat output of the furnace is combined with lower-than-expected-at-that-heat-output steam flow, you'll overheat the superheater.
robryk
boosted
Okay. I really, really want /sees my posts in their home tab/ and /can see my locked posts at all/ to be separate things. I want to the former to be totally open again, and I want the latter to be more restricted than it is now.
Please, please can we make this happen? #mastodev
robryk
boosted
RT @element_hq@twitter.com
‼️ IMPORTANT: Please upgrade Element to address a critical security update. For more background see ➡️ https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients
https://element.io/blog/important-security-update
🐦🔗: https://twitter.com/element_hq/status/1575155711054680064
robryk
boosted
2677. Two Key System
title text: Our company can be your one-stop shop for decentralization.
(https://xkcd.com/2677)
(https://www.explainxkcd.com/wiki/index.php/2677)
robryk
boosted
I'm looking for an USB XLR interface that's Linux-friendly. Currently I'm using Behringer UMC202HD and it's constantly problematic.
Boosts welcome!
I enjoy things around information theory (and data compression), complexity theory (and cryptography), read hard scifi, currently work on weird ML (we'll see how it goes), am somewhat literal minded and have approximate knowledge of random things. I like when statements have truth values, and when things can be described simply (which is not exactly the same as shortly) and yet have interesting properties.
I live in the largest city of Switzerland (and yet have cow and sheep pastures and a swimmable lake within a few hundred meters of my place :)). I speak Polish, English, German, and can understand simple Swiss German and French.
If in doubt, please err on the side of being direct with me. I very much appreciate when people tell me that I'm being inaccurate. I think that satisfying people's curiosity is the most important thing I could be doing (and usually enjoy doing it). I am normally terse in my writing and would appreciate requests to verbosify.
I appreciate it if my grammar or style is corrected (in any of the languages I use here).
Joined Nov 2020
