EEVblog 1406 - DC Circuit Transients Fundamentals 

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

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

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

Haha, awesome getting the Fonz involved with electronics.

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.

Great class, thank you.

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

Loved it!!

63,2% is 1-1/e

Can someone explain to me what L stands for (if so)? As for C -> Capacitor and R -> Resistor, L does not work for Coil nor for Henry. First i thought that, as C is used for Capacitor, coiL is using the last char for inductors.

AvE spoiled Dave... 🤣

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

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

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.

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.

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!"

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.

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

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.

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

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

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.

Love these fundamental videos a lot :D

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.

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.

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

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.

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

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

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

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?

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.

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.

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.

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

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 ;)

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.

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

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

Referenced videos: EEBblog2 "Calculating the Energy in a Capacitor": ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-3MtK035qiT4.html EEVblog "Schmitt Trigger Tutorial": ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Ht48vv0rQYk.html

@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?

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%

Good video and 1a explanation, but I have a serious question about all this: Isn't this all High School physics? Like should not everybody know this who was not a school dropout? I ask in all seriousness as this was High School (I think 10th grade) physics at least here in Germany in the 90s. So some other perspective would be nice to know. Thx!

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

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.

Lol the flipping calculators, questions how many does Dave has…

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.

so how would you design a simple circuit to limit the inrush current? In a battery operated device for example, when you plug the battery in, if you have a large bypass capacitor as a first component (for purpose of noise reduction for example) it will spark the terminal and have lots of inrush current I would think.

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).

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

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.

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.

perhaps its LC rather than CL in case people abbreviate things to make it funny; measuring CL circuits current over time (CLIt)

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

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

Rodriguez Angela Jackson Donald Moore Kevin

I always understood Transients to mean the unexpected effects, like stray capacitance and Inductance due to pcb track or proximity etc?

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

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

Great material. Thank you.

Not entirely true, even a resistor would be a combination of R L and C if you look at it closely enough.

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.

brain too mush. I learn one thing and i forget the others need more brain wrinkles.

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

It is because ICEman the ELI would sound funny. LOL

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

Did I miss something? Why do we call it an LC transient when there is no capacitor in the circuit? Shouldn't it be an RL transient to compliment the RC transient discussed? I feel like LC means something else (inductor and capacitor together).

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

I love this series, it's like you're training me to understand your other videos betterah

Great video lesson! Hope to see more like these ones

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

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

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.

I wonder one thing. The magnetic field is caused only by flowing current. At the beginning non-charged inductor blocks current completely. So how it can build his magnetic field if there is no flowing current?

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

Me watching it after my circuit and networks exam

What is the ESR of the earth-moon capacitor? ;)

Bonn scott is an excellent electronics teacher 😁

About 63.2% the initial voltage rise rate will be dominated by DC resistance (series R and capacitor ESR), right? So the RC constant is the ratio of DC characteristics (initial circuit state) to the reactive characteristics (changing state), is it? But capacitor ESR is not strictly linked to charge capacity so 63.2% could change, is that not right?

What is the derivative of 4x^2+9?

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.

This is a good lecture honestly

Inductor are the same as series resistors!

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.

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

Lol I read “FARAOS”….

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

Isn't that more like the circuit functions like a short circuit before the capacitor, but not after, is more accurate, when it is discharged and there is no resistors in front?

Perhaps at time 20:26 in the video it is better to show ‘e’ (2.7182..) i.s.o. Pi (3.14…). Otherwise great video!

You forgot to say that the same voltage drop over the capacitors in series occurs when the capacitance values are the same, i.e. C1=C2=C3 >> Did you mean to say (at 6:02) - 'ideal capacitors', or 'identical capacitors', or possibly both at once? Q = Cn*Vn : because Q is universal over each, best represented by the concept that they are open circuit elements except for this curious concept of of a certain amount of charge (i.e. current for a certain time) being able to cross the gap as it imparts charge in the capacitance, and of course conservation of current in a particular arm of the circuit [yes, even with capacitance there - You can't park electrons on one plate unless you park 'holes' on the other.] So yeah, I'd heard of capacitative dividers... but I'm really here for the inductors.

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

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

So I guess you have to be careful when probing inductors with your oscilloscope in certain cases? You don’t want to blow the front end with a voltage spike.

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?

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

Hello deary white boar atgain.

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