Search results

  1. D

    Are Back EMF, Reverse Current, Reverse Saturation current, and Backfeeding the same?

    No. Could you ask a more specific question? These terms cover a wide range of subjects in EE as I interpret them; Motors/Magnetics, Semiconductors, Power Distribution... It just too hard to describe everything in one post.
  2. D

    The Bear Facts

    Also stupid hunters. They shoot the deer, then walk up to it thinking it's dead. The deer gets up and attacks.
  3. D

    How does a pulsed plasma thruster work?

    Also collisions with the outward moving electrons will push some of the plasma. The charged ions will also feel E and B field forces, like the electrons.
  4. D

    B Visit to Hayden Planaterium -- The projector is gone?

    I would guess that you could do a better job with a computer and some lasers now. I'm not sure the hardware is the problem with the content you saw.
  5. D

    What is wrong with this picture?

    Yup, just like what might happen when they try to open that gate.
  6. D

    How does a pulsed plasma thruster work?

    A short, hand wavy, description: When the arc forms, hopefully on the right side near the teflon, it creates the B field (out of the page). Then the moving electrons (up) experience the force you described ##\vec F=q \dot {\vec r}\times \vec B## (to the right). So that arc is propelled to the...
  7. D

    Receiver Circuit Question -- What role does this antenna capacitor play?

    "the earthy end..." Perfect, LOL. Because we all know "earth" is seldom really earth. I'd never heard that before, I hope it wasn't a typo. It's pretty much guaranteed that I'll steal this sometime.
  8. D

    The Bear Facts

    LOL. In my day of backpacking near Yosemite, we had a similar rule about hanging up your food in the trees. You didn't have to hang it up well enough to keep the bears from getting it, in fact that was often impossible, but you did have to hang it up better than the other backpackers did. That...
  9. D

    I dt without f(t)?

    Yes, I agree their notation sucks. In dynamic systems (control systems) it is common to leave the range out, with an assumption it's "all relevant history". This is because most of the interest is in the behavior (stability, etc.), not the actual operating points. One of the cheats you get from...
  10. D

    Difficulty with machining bismuth, any suggestions/tips/other ideas?

    I was thinking EDM. But, really, this is way above my pay grade. Maybe you should call these guys and ask them:
  11. D

    I Which kind of function is this?

    I'd vote for some 3-D fractal, like this one maybe: edit: I guess this isn't a function though. More like an algorithm. Functions can't be multi-valued, right? Plus maybe you mean 4-D; "a function of x,y,z". Anyway, I like the pictures.
  12. D

    What kind of plastic is best for this loudspeaker enclosure?

    I think this question is more about plastic sphere production than acoustics. I think you can use anything from an acoustic perspective. Of course some won't be optimal choices, but you can compensate with thickness and other parameters. I would be worried mostly about production costs, myself...
  13. D

    The Bear Facts

    Once hiking just west of Yosemite, my dog took off running down the trail towards some young black bear cubs. I called her back (best recall moment ever, BTW). Great, now I've got a dog on a leash that was chasing some cubs maybe 200 feet away with no idea where the mother was. That was really...
  14. D

    B XENON1T and possible dark energy detection

    Granted, I'm not the intended audience for Phys. Rev. D, and, I didn't read the paper, but... Is this paper really about a result? The only reference in the abstract to a result is buried at the end of a string of "We explore the prospects for...", "...presenting the possibility that these...
  15. D

    Studying How far can I get if I stick to self studying physics?

    There are LOTS of good physics undergrad programs that aren't an ivy league college. Maybe you could teach your parents that?
  16. D

    What is wrong with this picture?

    Pondering those rollers on the rails makes my brain hurt. This is a perfect example of why I can't be a mechanical engineer. I think trigonometry may be involved...
  17. D

    CNC laser exhaust

    So maybe we should file this under: "If I build a system the wrong way, how bad is it?" That is the hardest engineering question. IDK, but I do know that I've normally seen full enclosures. But sure, you can probably get away with it. That's probably how they do it in India, Cambodia, and...
  18. D

    Engineering Designing an Integrator Circuit with Given Absolute Gain

    Thanks for the referral, but I already know what an integrator is. Better than the person that wrote that second link. That is a 1st order LPF. If you remove R2, it's an integrator. This is assuming we ignore the fact that op-amps aren't actually ideal. Fortunately, the first link has it...
  19. D

    Engineering Designing an Integrator Circuit with Given Absolute Gain

    What? This question doesn't make sense to me. Integrators don't have passbands (according to me) the gain is essentially infinite at DC and constantly decreases (inversely proportional to frequency) forever. Of course there are some real issues in the real world, like a low frequency pole, but...
  20. D

    Engineering Finding out the input impedance in a negative feedback op-amp

    No! The designer should assume that the input impedance hasn't been characterized. They should assume that: 1) It isn't a required screening in manufacturing. or 2) The marketing people didn't think it was worth the effort to do the characterization and to publish it in the "typical" section...
  21. D

    LTSpice functionalities regarding its Frequency Domain Analysis

    I have nothing useful to add about LTSpice. But, if you are seeking "frequency response" or "Bode plots", those are only defined in terms of sinusoids. If you want to do a different transform, like wavelets, let's say, you need to explicitly say that. "Frequency response" implies you have a...
  22. D

    Audio/Video Anything that can be done for this ailing Onkyo Tuner?

    Not a total waste, probably. This is an important lesson in fixing electronics, I think. "Experience is what you get when you don't get what you wanted."
  23. D

    Engineering Finding out the input impedance in a negative feedback op-amp

    Also, (totally off-topic): I think it's interesting that all of the academic op-amp stuff always uses LM741 as their example. Perhaps the first modern op-amp? But, I started doing design work in 1980, and I have NEVER seen an EE actually choose that part. It was obsolete 40 years ago. Perhaps...
  24. D

    Engineering Finding out the input impedance in a negative feedback op-amp

    Yes, I think you're correct about the differential pair. I was being sloppy. In practice, the effect for a follower isn't normally significant enough to care about. Also, as you said, for MOS, the impedance is dominated by a huge input capacitance. This is one reason for the existence of...
  25. D

    Why are touchscreens becoming popular in test equipment (scopes, etc)?

    Yes. But the key thing here is the user interface. The pilots need what they need now, not 3 levels down in a menu. OTOH, Airbus may disagree. The avionics equation is that a good user interface and reliability counts; cost, not so much. Most often, it's the pilot that will crash the plane. So...
  26. D

    Why are touchscreens becoming popular in test equipment (scopes, etc)?

    But would you actually pay for that? Would anyone else? That stuff is expensive.
  27. D

    I Where does the "i" go

    The other possibility is that they are assuming that you only care about the real part of the equation, and they are saying it's a generic sinusoid. In that case B ≠ i(C-D). So, because they've shown the answer is a sinusoid they switch to an alternate expression for it. i.e. Re( (C+D)cos(wt) +...
  28. D

    Engineering Finding out the input impedance in a negative feedback op-amp

    Which amplifier? Yes, this is often the solution, but a bit more rigor would be appropriate. Not all amplifiers are built the same way.
  29. D

    I Where does the "i" go

    Then I would guess they are assuming A and B are complex numbers. Otherwise it doesn't make sense. You are correct, the "i" can't just vanish. Anyway, it's in the definition you provided: C+D) cos(wt) + i (C-D) sin(wt) = Acos(wt) +Bsin(wt)
  30. D

    Why are touchscreens becoming popular in test equipment (scopes, etc)?

    If you ever get the opportunity to take apart a 1960-1990 era instrument with a significant user interface, it's worth the effort, IMO. The mechanical packaging design, manufacturing engineering, and component design is impressive. OTOH, there sure are a lot of things that could break. I guess...