Thanks Dave, these fundamentals taught me a lot. More please!!

50 years ago an old chap who encouraged me used to say "remember, two things that can catch you unawares are back emf and charged capacitors!"

Oh my God , I am not gonna lie , I have a test on circuits and networks in 2 days Thanks Dave !

One of my first screwups in electronics was unplugging an energized stepper motor. The collapsing field fried the motor driver. Those hundreds-of-dollars lessons stick.

One of the most important concepts ever presented to me was to think of time zero in a circuit.. and then it starts. Before the circuit comes to operational stasis, it it a mess of inrush currents, charging up elements and even heating. Transient analysis is critical. Same at shut down, collapsing fields and discharging. Everything must be accounted for, not just steady state. Not only is inrush current a problem charging DC filter caps, so is the haversine wave after a bridge rectifier. Because the cap can never charge to the very peak voltage of the haversine, every time the voltage approaches the peak voltage, the capacitor is a very low impedance load for a very short time period. To eliminate this cyclic but very brief short circuit a current limit device should be used between a rectifier and filter cap..this is where inductors are quite handy. This is trivial with most 'small' circuits, but in large amplifiers, cap banks in the range of tens to hundreds of thousands of uF are quite common, and haversine peak charging currents can easily destroy a large transformer over time. Another solution is to use a mosFET in series between the rectifier and cap bank.. driven by a threshold detector to have very low R below most of the haversine voltage wave, and to start having higher R above a threshold point selected to be near, just below, peak voltage.

Had a cooling fan hooked up to my Raspberry Pi and when I unplugged the power it fried the TVS. It looks like nothing else got damaged but a lesson about inductance was learned that day.

You've left me with a .5M of dust on the floor and tangled in cobwebs. I got my EE degree almost 45 yr ago when I went into engineering SW development; haven't chased electrons in WAY too long. A refreshing review... maybe a "new" hobby re-emerging (if I can find my breadboards and the drawer storage box with all my components and supplies in my storage unit). Thanks.

O man, so good to see you again in the fundamentals...you taught me a lot ...

Brilliant, can't get enough of these theory chats. (: Thank you!

I was a fool to take an ITT Tech course back in the 80's to get an EET cert for WAY too money. I wish we had instructors like you back then. You explanation was much more clear and concise.

The 63.2% comes from 1-exp(-1) (%), which is the voltage factor at t = T = RC, ie the % of total voltage at the first time constant.

Got my inductor lesson from the flyback transformer on a color TV. Unforgettable lesson.

"What is the capacitance between the Earth and the moon?" Physicists: 1.29284E-21 farads! EEs: Zero. It's zero.

Just repaired a ups that used sizable inductors to create a 800v dc bus. Biggest inductors I've seen in a boost converter so far.

these fundamentals are a great refresher Dave..about time ya got back to being useful and not just waffling on all the time! :P thanks mate

At age 14 I built a circuit to shock my friends, with a 9V battery, momentary switch, and large inductor. Convince them to hold on to the wire, then let go of the switch. I was not popular as a teen.

Good information. This was review for me, but I always like to refresh my memory. I worked on high voltage dc-dc converters in my previous job. This theory came into play on a daily basis. When I saw your initial series caps, I was thinking, “you’re going to need some balancing resistors.” I wasn’t going go bring it up, since you were describing the ideal theoretical concepts, but I was glad to see you mentioned it. Another thing I learned on the job is HV MLCC caps lose most (like 75%) of their capacitance at their rated voltage. I learned about the back emf diodes protection back in my military training, but I don’t think they teach that well in college. Most BSEEs I’ve worked with design relay drives without it.

Love these fundamental videos a lot :D

In two movies you gave me more knowledge than 6 years of a school.

Please keep doing these fundamentals videos. The more I go forward in my education the more I find the need for falling back on fundamentals to understand. I hope you can make videos on wireless communication fundamentals and signal fundamentals. Topics on communication engineering please.

this was the exact video I've been wanting and needing for a long time, but I couldn't put my finger on it. Thanks.

Circuit transients is what was transitory in my mind always. Quite stabilizing now,....Thanks for awesome videos!!!

Thanks Dave! Great review!

Brilliant, my electronics knowledge is now expanded, thank you.

Very good video here, Dave! Knowledge like this is what makes a good engineer. Keep up the good work.

Nice video - going back to your roots. Good job Dave!

I have had not time to watch this channel during the last 4 years, but now the news cycle is a bit slower than it used to be. I'm ready

this is a lifesaver! I will have my electronics exam 3 days from now, and the hardest thing for me to understand from my classes was capacitors and inductors.

Great video series Dave, real stuff! Thanks 👍

Excellent presentation !!

Great video lesson! Hope to see more like these ones

Excellent tutorial on LC Transient behavior, much more useful practical knowledge than my EE professors who start out with all the physics and you lose touch with the practical application in circuit design. Thanks for taking the time to produce these videos, so useful.

Interesting to note that the only case of a capacitor storing a charge without any voltage source connected for an inductor is an MRI machine with its superconducting magnet that forever has (or at least until someone hits the red button) current going round and round to make the magnetic field.

This is a good lecture honestly

Thanks for making this!

Great material. Thank you.

Haha, awesome getting the Fonz involved with electronics.

Dave isn't DC "AC with infinitely long wavelength"? xD

9:32 - "not that electron current flow rubbish" 😂

What you call big "T" is Tau in my books. I like these videos. Really takes me back. Thank you Stan Graff, wherever you are. My old proff.

Great class, thank you.

Masterclass. Nice and easy.

Very useful video, thanks much ! Alan Wolke also has some excellent videos on LC series and parallel circuits and diode snubbers for relay coils.

Great stuff.

Loved it!!

I'm looking forward to the follow-up transformer lecture. We deal with a lot of primary measurement CTs in protective relaying in electric power transmission (nameplate ratings on the order of 3200A:5A [N=240]), and inadvertently open-circuiting the secondary of one of those under load gives an impressive, and potentially fatal, demonstration of Lenz's law.

Very informative!

I love your channel Dave. Plus you're freaking hilarious. Keep it up. Greetings from Canada.

Right over my head, but Thankyou, I'll be probably googling this in 10 years time :)

Ohhhh DC transients! Waiting for someone to really explain this for a while!

Some SMPS also includes NTC series resistors to limit current inrush. As it gets hot the resistance decays creating a soft start effect. (Sorry for my english. Hello from México).

Been in electronics the whole adult life (and some before). Now that I am semi-retired, electronics math theory like this still makes my brain hurt. lol

Grasias x los videos sige adelante compartiendo

This one was remarkably informative. Please make a video on LC oscillations. Will be of great help 🙏🏼🙏🏼.

Yes Dave, move this to a new blog. I will subscribe.

Very cool how you explained L times di over dt ....

Just to add some tidbits about Inductance, that is why start and stopping of high power electric motors like in an industrial settings is its own science by itself to not fry the motor and the electronic driving it or popping all fuses.

Salvaged components from an old VCR.. was amazed with how many inductors was used right through the board.. the board seems to present a quality that just preceded the move to smd.. lots of good pots etc.. Made me wonder what are the practical uses of inductors...someone liked them.. I did some googling out of curiosity and found articles that seem to suggest that some desighners avoid them... and listed some practical applications and explanations... still enjoying it...

I love fundamentals friday on mondays! I look forward to the transformers video, and hope you do a piece of choosing inducers and how to size them for the current, likewise how to choose/design transformers for AC circuits and how much voltage they can handle

2:30 an even more fun question would be, what is the _elastance_ between Earth and the moon. That would trip a few people up for sure.

Good day, Like the videos, thank you, Jean-François

nice calculator you have there. Seems to also change with the passing of time!

There actually are practical inductors with true zero DC resistance, superconducting magnets. The coils in those magnets are usually a complete short circuit (closed current loop). In order to charge them up they open up the loop, connect a power supply across the gap, slowly ramp up the current until the desired magnetic field is reached, and then close the loop again and disconnect the power supply. As long as the coil is kept at a low temperature so that superconductivity is maintained the magnetic field will stay and the current will keep flowing (without any voltage no less!) indefinitely. Fun fact: In practice they don't actually physically open the loop, they just heat up a small section of superconductor to above the critical temperature so that it becomes resistive. Because the resistance of the coil is zero in steady state all the current will flow through the coil and nothing through the resistive section, so the resistive section essentially acts like an open circuit even though it's a conductor (Other fun fact: the windings in a superconductive magnet are usually electrically insulated against each other with copper. During superconductive operation no current will flow through the copper, but in case of an unexpected loss of superconductivity - for example cooling failure - the copper will short out the coil and limit the voltage spike generated by the inductive kick). Kirchhoff's laws become funny when R becomes zero.

What's really interesting and new to me, is that if you have series caps of different Farad ratings, they should end up with different voltages across them.

Thanks. I am going to use RC timer on microcontroller because some time it do funny thing when I power it on.

this reminds me why i didn't take electronics engineering back in college. ahh good times

One of my favourite channels. The other is Fran Lab . You should get together sometime it would be truly awesome.

If I only had Dave back in 1971. I might have made something of myself.

159uf is the capacitance between the Earth and the Moon. Google is a wonderful thing.

9:45 Or, or, or you use your left hand, for the proper current flow, that is, the electron flow, and you also get the direction of the magnetic field ;)

36.8% Hmm 0.368 is 1/e that can't be a coincidence. Well, he found the number T by putting a slope line in the beginning, so we need to find a derivative at t=0. Derivative of Ve^(-t/T) = -Ve^(-t/T) /T Plug in t=0 and you get -V/T. That's the slope of the line, and we know that it is equal to V when t=0. So, the equation for the line is V - tV/T. The line crosses the time axis when tV/T = V or in other words when t=T. Plug that into the original function Ve(-t/T) and we get Ve(-T/T) = Ve(-1) What's that as a percentage of V? It is Ve^(-1) / V = e^(-1) = 0.368 = 36.8%

Great video. I feel like I come away with a much better understanding. Thinking about the earth and the moon in this context still makes my head hurt tho lol

Oh Dave, you missed a golden comedy opportunity right at the end to show you checking everything you just said in "Electricity for Dummies" ;)

Referenced videos: EEBblog2 "Calculating the Energy in a Capacitor": kzfaq.info/get/bejne/abOkfpNkmtfNhGg.html EEVblog "Schmitt Trigger Tutorial": kzfaq.info/get/bejne/ftpka9mnldi1iZ8.html

Oh yeah, AC next I realy struggle with that....cheers.

I was so hoping to see demos of charge-discharge...

I hope there will be also videos about AC (for the practical reason like building power supplies, using 3 faze motors or safeyetc.)

Energy of a capacitor (1/2)cv^2, Energy of an inductor (1/2)Li^2, energy of a moving object (1/2)mu^2, energy of an elastic medium (1/2)kdx^2. Nature if wonderful. :D :D :D

Just some fun with a transformer: get a friend to hold on to the secondary and use a AA on the primary for a shocking good time.

and things are getting interesting... fast forward to advance players..

Hello Dave, I love your videos. Your knowledge has helped a lot. I have a request, can you please make a video about finding the loop stability when we are creating a discrete linear voltage regulator using OPAMP and a BJT? I have tried a lot but I can't seem to find a way to find out the stability and the gain and phase margins.

Who would have thought that Joe Mangle would know so much bout leccy. 👍

So, Laplace transforms (S-domain analysis) next?

Man, I didn't even get this pushed to my subscriptions or notifications. Thanks, overlord google.

I always thought of RC as Radio Controlled and LC as LIGHT SABER CONTROLLED! 😆

Oh man, I'm going to have to use my confuser more often.

Bit stuck Dave in that Lock down. Stay safe mate.

I wanted to make a four layer capacitor to function as a single component dc transformer. The two outer plates can function as the "primary" and the two inner plates could function as the "secondary" and if you increase the surface area of the primary or secondary you can alter the voltage .....

Great

30:43 biggest misconception ever. Ignition coils are coupled inductors at best, but are still primarily used in transformer mode

Why did you feature different calculators throughout the video ? Thanks a lot for this video !

Series capacitors= Parallel resistors/ Parallel capacitors= Series resistors!

20:25 Interesting value of e.....

Since High school,I still don't have any idea why do we say both capacitors plates have always have exactly equal and opposite charges regardless of the geometry of the circuit. They say one electron will reply the one on the other plate but it's just one in a million possibilities I can think of. It's not convincing.

Capacitance from Earth to moon is cca 0.2F or 200mF

Here is a fun experiment: wind an inductor (5 turns for example) on a ferrite core. Measure the inductance. Wind another 5 turns (on the opposite side and in the same direction) and connect them in parallel. Is the total inductance half of initial 5 turn inductance?

20:27 euler's number is 2.71828

@2:35 I calculated C = 1000 x 8.9E-12 x 4.7E7 / 300E3 ≈ 1.4µF (roughly) Considering only the moon surface, both electrodes as an approximation. Does that make sense? I mean... really?

I'm a complete amatuer with no formal training so I apologize if this makes no sense but at 18:30 when you mention the in rush current being larger due to no charge on the capacitor, is that why you get a pop when plugging in audio gear?

I typically say LC and LCR (like an in LCR meter), but when I just have resistance and capacitance, I typically say RC and not CR. I have no idea why. It appears to be common. It's just what I copied from teachers I guess. I wonder what's the history is behind that.