General > General Technical Chat
What do you do when fellow engineer wants to crash project?
tom66:
--- Quote from: Geoff-AU on October 10, 2022, 11:59:01 am ---All I know is I'm bloody confused by this thread
--- End quote ---
The guy is endlessly posting about how someone or something is conspiring against his employment/projects/job prospects etc., how the UK economy is going down the shitter and how he's trying to save it if only someone would listen. It's probably best to not rationalise it.
tggzzz:
--- Quote from: Geoff-AU on October 10, 2022, 11:59:01 am ---
--- Quote from: tom66 on October 06, 2022, 09:43:29 am ---Another treez/Faringdon post where I think the OP may be projecting a bit hard.
--- End quote ---
All I know is I'm bloody confused by this thread
--- End quote ---
Don't worry about anything in a thread by treez/faringdon, except where bystanders might be hurt. The guy has History.
Here's a recent complete barely literate OP from faringdon, "Totem pole gate drivers on the web are poor". It needs decyphering before responding.
--- Quote from: Faringdon on October 09, 2022, 01:27:45 am ---Hi,
All the totem pole gate drivers i find on the web dont have the "extras" that are needed to make this work well.
Eg, they dont have an upper Darlington for the upper txtor of the totem pole.
And thus they lack the added circuitry to sweep out minority carriers from the Darlington to make it switch faster.
They also lack the cctry added to sweep out the minority carriers from the lower PNP of the totem pole.
Also, the web offerings lack the diode used to reduce cross conduction.
As you know, the easiest way to do totem pole driver is to actuate the totem pole with a low side common emitter BJT to pull down the centre point....and a resistor to pull up the centre point..
But as discussed, the ones on the web are all pretty awful.
Do you know of any with the needed "extras"?
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T3sl4co1l:
--- Quote from: niconiconi on October 10, 2022, 10:37:57 am ---At the fastest time base, Tek 7104 sweeps "faster than light". Though I never saw a screenshot to show it. TekWiki has a screenshot but the beam moves "only" at 95% of c.
--- End quote ---
Phase velocity, not group velocity. ;)
The same as saying, you can spin a flashlight and claim the beam goes "superluminal" at whatever great distance, where the flashlight is presumably still visible (and for suitable laser-based value of "flashlight", that's easy enough to test). Clearly the beam, no matter how you're shaking it around, still travels at the speed of light as it goes. The variation in amplitude travels at the speed of light; the correlation with nearby points in space is irrelevant. I could just as well flick the switch on and off and claim that, because the wavefront changes at all points (at some given distance) simultaneously, the (phase) velocity is infinite. :)
Tim
niconiconi:
--- Quote from: T3sl4co1l on October 10, 2022, 02:54:23 pm ---
--- Quote from: niconiconi on October 10, 2022, 10:37:57 am ---At the fastest time base, Tek 7104 sweeps "faster than light". Though I never saw a screenshot to show it. TekWiki has a screenshot but the beam moves "only" at 95% of c.
--- End quote ---
Phase velocity, not group velocity. ;)
The same as saying, you can spin a flashlight and claim the beam goes "superluminal" at whatever great distance, where the flashlight is presumably still visible (and for suitable laser-based value of "flashlight", that's easy enough to test). Clearly the beam, no matter how you're shaking it around, still travels at the speed of light as it goes.
--- End quote ---
Yes, normally it's the case and is the correct answer to common paradoxes. For the purpose of radio engineering, the signal velocity of guided waves is the group velocity, which is understood as the speed of the entire packets of modulation, while the phase velocity can be faster than c, but it's inside a packet of modulation, thus not the actual traveling signal.
But in those exotic experiments I linked earlier above, using special materials with negative index of refraction (and sometimes even in waveguides below cut-off), this definition of "signal velocity" also breaks down, the apparent group velocity is also faster than c. A better way to phrase that is anomalous dispersion makes the definition of "group velocity" meaningless. Expectedly, this generated huge confusions among an army of engineers and even physicists, and there was a big debate on how to define signal velocity in these settings in the late 90s and early 00s.
The consensus is that the only reliable definition of the true signal velocity that always "works" 100% of the time is Sommerfeld precursor (or frontrunner), an esoteric concept from theoretical E&M. Sommerfeld basically showed, at the instant a signal is transmitted, theoretically there's a suddenly change of E&M field with an extremely tiny magnitude that immediately travels across the medium at c0, this sets the real upper limit of signal velocity under all circumstances - which is the speed of light in vacuum. So there's no FTL signaling even with faster-than-light group velocity, as expected. This can also be seen as a mathematical formalism of "at the moment you push the ON button of the signal generator". It's predicted by Maxwell's equations while practically undetectable (which is the answer to the paradox that "if the precursor always travels at c0, you can just ignore the dielectric constant of the medium, but in practice you can't, why?").
It was quite a rabbit hole to read through the literature. More links for anyone who wants to waste time on this useless theoretical problem with no practicality.
Abnormal Wave Propagation in Passive Media
(this experiment shows time domain and VNA measurements, the group velocity is convincing demonstrated to be faster than light, though there's still no FTL signaling).
https://moscow.sci-hub.se/1435/ac20c3f7657cf7b91e8026d62a1be63f/mojahedi2003.pdf?download=true
Superluminal signals: an engineer’s perspective (and 5 more papers from the same debate).
https://www.ate.uni-duisburg-essen.de/data/postgraduate_lecture/Cologne_Counterposition.pdf
SiliconWizard:
--- Quote from: rstofer on October 04, 2022, 11:51:16 pm ---
--- Quote from: MK14 on October 04, 2022, 06:54:47 pm ---Example:
You work for Elon Musk, and a completely crazy new big project comes up. Which, by the sound of it, sounds totally impossible/implausible and impractical. It is probably best to steer clear of that new project, if you can. E.g. A new Hyper-space time machine, made out of hot-air and hyper-nuts juice.
--- End quote ---
The guy who started Tesla and made electric vehicles go high end and mainstream? Or the guy who introduced Artificial Intelligence to self-driving cars? Or the guy who started SpaceX and has a pretty good track record compared to his competitors (there are at least 10 with little recognition). PayPal is involved here somehow...
I would jump on any project he comes up with. Win, lose or draw, it would be a hell of a ride.
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Yep.
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