Видео

These lectures are a river of gold

An oriental motor sales rep came by once and told me that their latest series of steppers had a 30 micron airgap. I stopped him and made him double check because that was so hard to believe. It was clearly the first time that sales rep had ever really thought about what that implied. "Huh, I guess that is pretty impressive actually", he said.

Something that I wondered for a long time is why not just use the neutral to ground the metal case. After all it's at the same potential as ground, right? Why not save copper? There's a good reason of course: if the neutral wire ever gets severed anywhere between the service panel and the appliance, it would cause the appliance case to become live, even without any short anywhere. Like let's say the appliance is a stove, with a heating element between live and neutral. You turn it on, not realizing that the neutral wire is broken; because of that, there's no current through the load, so there's no potential drop across the heating element, so the disconnected neutral line gets energized to live voltage, and if the appliance case is "grounded" by the neutral you get a shock. That's why the appliance case needs its own ground connection independent of the neutral.

Dan, great lecture as always. By the way I think this looking-at-you detector does have to do with vision. Because the human eye is not just a sphere, it also has a lens which -- if he's looking at you and focused on you, it focuses your image on his retina perfectly. So that will make the eye a perfect retroreflector and correct for any imperfection in the eye's index of refraction, and the glasses he's wearing will only help! Also, you might find this interesting -- E.T. Jaynes points out that the best sensors are optimized to mostly reflect EM waves, rather than to absorb them like a solar panel would. So it's not even a coincidence that the retina is reflective (and so are CCDs). It turns out that you get a better signal-to-noise ratio that way. It's an off-hand remark in his paper "theory of radar target discrimination" (1991).

I like this man because he insert history of technology everywhere

This guy has me in tears. Engineering is so good.

Keyence's "handheld CMM" uses a camera to image a quartz cube with a fiducial grid embedded inside to measure the angle of the cube.

nice.

All this stuff you get taught at university is very easy to forget - until you actually need it in practice, and then it's the most important thing in the world 😂

The energy method for calculating forces in moving iron actuators is one of multiple methods. It should be noted that this method does not account for the flux that escapes from the magnetic flow path. In the case of a well designed solenoid with a ferromagnetic case these losses are small. In many designs these losses are not negligible. If one wants to delve more into solenoid design I would suggest reading Electromagnetic Devices: by Roters. As he had noted the profile of the armature interface can also have a large effect on the profile of the force curve. This can also be significant. Thank you fizzym for making these lectures available! I appreciate all the content from Dan Gelbart. He never ceases to amaze me!

~20min mark talking about distortion is a bit unclear, the amplifier doesn't naturally cancel or fight any distortion, it is just the characteristics of a typical real world amplifier are such that, when used at low gain, they will not introduce a lot of distortion, that is a byproduct of the technology at the time (and to some extent even now), not a law related to amplifiers in general that is why it is quite common in electronics to see couple opamps in series to do work which one could do, and a lot of times extra opamp is "free" anyway, since there usually is a number of them in a package

I don't understand the term bandwidth in this context. Anybody?

The quality is fine you must have been born recently if you think otherwise. And what do you want them to do exactly, go back in time?

If one of the three phases was made to lead or lag, wouldn't you lose the virtual ground?

To bad the resolution is so bad. I can't read the equations.

It would be more helpful for students if you could upload a higher quality video. Hard to read the board.

Very bad audio in some part . Who played volleyball with microphone

Very informative and great experience

I am not a student, I own a company that designs electronic products. One of my engineers stumbled on your lecture on Tellurometers while researching a project we are working on. Since then I have learned a ton from you. Thank you for sharing your work and simple explanations. You are a talented instructor.

@fizzym: I'm so happy to listen, thank you so much for sharing all those videos!

I love watching anything with dan gelbart

Thanks a heap for uploading these, if you have any more then please upload them too :)

There's an interesting phenomenon with audiophiles swapping normal opamps for high bandwidth ones and those new opamps oscillating at like 10mhz and dissipating a watt....

On Governors is a must read!

Never thought of a balance as a null device. Very nice lecture, thank you for posting.

An intuitive understanding of why an induction-motor can keep running when the starter-capacitor is disconnected: ruclips.net/video/Uuh_T648J_8/видео.html

Thank you so much for sharing, (Dan Gelbart is brilliant and a great teacher, why didn't I hear of this guy before). Looking forward to watching all videos in this series

Point of nuance: Not all rotating-field motors are constant-angular-speed - the chief exception is the induction-motor where the slip (reduction in angular speed) is dependent on load (torque). I suppose this shall be covered in the next lecture. 1:14:16

30:52 "Public humiliation as a motivator for innovation" - I'm gonna write that one down ;)

Would adding a polarizer and a quarter wave plate to the sniper-scope make it "invisible"?

The passive-microwave "bug" 27:00 , if you are interested, is explained in detail here: ruclips.net/video/NLDpWrwijE8/видео.html

58:50 another good analogy for a tellurometer is that of a wall-clock. There are three "hands" - hours, minutes, and seconds. As such, you can visually resolve one second in a half day (20 parts per million). This precision is afforded as, during the period (i.e. half a day) the three hands always have a unique combinatorial position. Any fine error in reading the hours-hand can be corrected by looking at the minutes-hand and so on.

Interesting note: 41:12 The "printed inductive loops" scheme is also used on most "tablet-pen-digitizers" - Wacom and whatnot.

Errata: At 11:12, the envelope shall be that of a phase modulation (i.e. shaped like a fullwave rectified sinewave) rather than (the illustrated) AM at 100% depth of modulation

1:16:48 - an interesting question that nobody asked: The angle alpha is lambda/d --> for non-monochromatic light, how can the beam-combiner (mirror on the blackboard-sketch) be practically implemented? Remember - the two (+1 and -1 order) beams shall now be split into a 'rainbow'.

43:05 Michelson wished to use it to (dis)prove ether, ironically, 100 years later, the same basic experiment was used to demonstrate gravitational waves :)

For the explanation at 2:58 - Remember, if you wish to readout the sensor electronically, you's STILL need _quadrature_ or something equivalent. One way to achieve is to use a Vernier-disk as the stationary disk. In other words - if your main encoder wheel has 1000 stripes, you make the stationary disk with 1001. Then two detectors can resolve quadrature. If you are worried about eccentricity (as in the example of a theodolite) use four detectors, and average cross-wise.

35:14 interesting about 950nm is that this wavelength is highly absorbed by (atmospheric) water-vapor, meaning that sensors at this wavelength are relatively unaffected by sunlight - most of the 950nm from sunlight is eliminated by atmospheric water-vapor.

Interesting new development - most red and IR-sensitive photoelectric compositions (especially emitters) are highly temperature-sensitive. Gallium nitride, on the other hand, is less so. If insensitivity to temperature is critical, and immunity to ambient light can be provided in a different manner, it is often advantageous to use GaN or InGaN based optical devices - either blue, directly, or photon-converted amber (PC Amber) if using conventional (Si-based) photodiodes that don't like blue wavelengths 33:14 .

Errata - plants don't absorb 30:36 green (one of the mysteries of evolution, as to why this evolved this way - perhaps availability of chlorophyll-like molecules?) - rather they reflect it, preferentially absorbing red and blue.

11:28 (errata) *Odd* multiples, 120 Hz, 360 Hz, etc.

I'm binging these lectures. Thank you for the upload.

I think that if the video quality was improved, these lectures would gain more traction. Big thanks to the uploader and Dan Gelbart for this awesome content.

1:06:10 - I take issue with the statement "the phase shift can be much more than 180 degree" --> How? In a 2nd order resonant system, it shall be _exactly_ 180 degree at its worst. A sharp resonance-peak makes the transition from 0 deg to 180deg _much_ faster, when sweeping frequency, but it will never exceed 180 deg, no matter how high the system-Q. @OP - do you perhaps have an explanation to the meaning of this statement?

it is so great to see all those lectures. Thanks a lot. How did you become the videos? Are you student of Gelbart?

Great lecture series, but 1/3000 error in the gravity case is 0.03% not 0.3%!

very nice to see more Dan Gelbart videos! But the quality is not good...

WE NEED MORE OF DAN GELBART!

Thank you for this priceless lecture of this great engineer.

I am so hype to watch all these. Thank you so much