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Cake day: August 4th, 2023

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  • TootSweet@lemmy.worldtolinuxmemes@lemmy.worldTrue story.
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    12 hours ago

    Python rebuilds don’t cause (noticeable) problems for AMD64 Arch Linux.

    And any time anyone offers any kind of help on the Arch Linux Arm forums to try to help resolve the issue, the admins ignore and/or lock the thread. They’re not open to help and the people on the forums are super frustrated about it.




  • Well, to say “the voltage differential between A and B is positive” is saying exactly the same thing as saying “the voltage differential between B and A is negative”.

    There is such a thing as voltage differential. And the voltage potential at one electrode can be higher than the other, or the voltage at one can be lower than the other. But given that “voltage” isn’t really a thing except in relation to something else, there’s kindof no such thing as “negative voltage” or “positive voltage”. Just voltage relative to some other electrode.

    And if the voltage of one line is higher than the voltage of a reference (“ground”), then the voltage is said to be “positive”. If it’s lower, it’s said to be “negative”.

    I don’t think “negative voltage” is any less a thing than “positive voltage”, really, but neither one is really a thing except in relation to a reference. Which is to say you can’t connect a single electrode to an instrument and measure the voltage of that single electrode. That would be meaningless to try. You can only measure the voltage of an electrode by connecting your instrument the electrode and a reference.

    Hopefully that clears it up.


  • I’m not an expert, but I think I know what the deal is.

    First off, the voltage of a single line has no meaning except relative to the voltage of another line. (Just like, say, “in motion” or “at rest” have no meaning except relative to a frame of reference. “At rest” relative to, say, the earth or the sun or the galactic center or car interior or whatever.) If you step on one rail of an electric rail line, nothing happens. You don’t even feel anything. If you step on the other, similarly nothing. If you bridge both, <southpark skier voice>you’re gonna have a bad time</southpark skier voice>.

    “Ground” isn’t zero volts in any objective sense. And Vcc isn’t 5 volts (or 3.3 volts or whatever) in isolation.

    And in fact, it’s only convention that ground is arbitrarily labeled “zero” and Vcc is 5 volts rather than Vcc being labeled zero and ground being labeled -5 volts. (Ok, it’s a little more than just convention. The latter would be awkward in practice. But it would be consistent, and you could do all your circuit design that way, just like if you labeled the white keys on a piano “Z”, “Y”, “X”… instead of “A”, “B”, “C”… You’d just have to think differently about it to make it work.)

    So, I think what’s going on here, and we’ll pretend “Vcc” is 5 volts (relative to ground) just for the sake of this example, is that basically:

    • The voltage differential between ground and Vcc is 5 volts.
    • The voltage differential between Vee and ground (and the order in which I list “Vee” and “ground” here is important) is 5 volts. (If I listed “ground” and “Vee” the other way around, it’d be -5 volts.)
    • The voltage differential between Vcc and Vee would be 10 volts.

    So, for instance, if the device has some components that operate at 5 volts and some that operate on 10 volts (I dunno, let’s say the CPU requires 5 volts, but the… I dunno, optical drive motor?.. requires 10 volts), you can get 5 volts by using Vcc as my source and ground as my sink, and you could get 10 volts by using Vcc as my source and Vee as the sink.

    That all make sense?

    And to one of your specific questions:

    Is this a figure of speech or can voltage actually have a negative value?

    So, what qualifies as “negative” and what qualifies as “positive” is just convention. Just like what qualifies as the “north” end of a magnet and what’s “south” is convention. (I guess “north” and “south” refer to which direction a magnet points when used as a compass, but then again which end of the Earth is “north” and which end is “south” is just linguistic convention as well.)

    In the same way, what we label “positive” voltage and what we label “negative” is convention. However, we do have an established convention with voltage. (And with poles of a magnet.) Just because we “made up” what qualifies as “positive” or “negative” doesn’t mean there’s any disagreement on the topic. So unless you purposefully switch your language just to be contrary, you’re not going to get funny looks or requests for clarification using the terms “positive” and “negative” for electrode voltages.

    However, if line A has a lower voltage than B (and what’s “lower” or “higher” is convention) we can say that the differential between B and A (again, order is important) is negative whereas the differential between A and B is positive.

    The analogy between voltage and pressure only goes so far, but in this case I think it’s helpful. If tank B has higher pressure than tank A, you can say the pressure differential between B and A is negative. Similarly, you could say that the air pressure differential between sea level and the peak of Mt. Everest is negative. (Though, with pressure, there is such a thing as “absolute zero”. “Perfect vacuum” is technically a meaningful concept. I don’t think there’s any such thing as “absolute zero” for voltage. Only “differences” between voltages on different electrodes.)









  • $130k after 2 years? 2 years after I started I was making like… $60k? That’s not even counting the 4.5 years I spent starting a startup and making nearly nothing.

    That said, I don’t live in Silicon Valley or anything. Pretty low cost-of-living here. Probably a big part of the discrepancy. I didn’t reach $130k until like 20 years of experience in the industry.