Howto repair switch mode power supplies #3: Inductor in electronic circuits P1

In switch mode power supplies (SMPS) the chopper transformer plays a major role. A transformer is built from two magnetically coupled inductors on a magnetic core. Therefore, in a simple approximation here we look at the behavior and functionality of a single inductor in an electronic circuit. Furthermore, buck and boost DC/DC converters use simple coils instead of transformers.
The most important detail what we need to understand, is that an inductor is a passive electromagnetic device, where electric and magnetic energy is being temporarily accumulated, and these two different types of energy are being transformed from one to an other. To understand the concepts behind energy transformation and conservation, in the first I show similar concepts on a simple mechanical spring, where it is more straightforward to visually see and follow these concepts in action.
In the case of a mechanical spring, external mechanical energy is first being transformed into elastic/deformation energy, and later this will be transformed back again into mechanical energy.
For comparison, in an inductor an external electronic energy (current) will be transformed into magnetic energy, thereby magnetizing the inductor. Later this magnetic energy will be transformed back into electric energy though electromagnetic induction, and the core is demagnetized.
In this video we cover the basics of the magnetic field lines, and the mechanical shape/construction of an inductor. Some simple experiments are done on a spring and on the inductor, making it into an electromagnet. We look at the properties of the toroidal vs rod type solenoid inductors. In SMPSs the toroid inductors are used most frequently because they provide low stray magnetic field, and high electric/magnetic energy conversion efficiency. The usage of inductors as DC chokes is also being covered together with the electromagnetic noise.
The ferromagnetic nature of the magnetic core is also explained, without going into any detail, and especially without discussing at all the Maxwell's equations (like the Lorentz force, or the Biot-Savart law). This is because in these videos I am trying to grasp the basic ideas for every hobbies, and not everybody likes deep mathematics. In fact, for repair purposes knowing these laws is not even necessary.

[@stc2330]

Finally found a site that explains electronics so that my tiny brain can understand it

[@peckelhaze6934]

For me, this method of presentation is perfect. Everything you talk about is clear and very well explained. I look forward to other videos from you.

[@DonkeyLearningIT]

Thanks for the positive feedback. Finally I had time to upload the next episode, related to linear power regulation. It is not my best video due to the "boring" topic. Still, this linear regulators are used to generate reference voltages in every powers supply, making them an important topic. When you got time on your hand, just watch the new video, and let me know what you think.

[@peckelhaze6934]

@@DonkeyLearningIT It is nice to see these still on KZbin as they are good for a refresher course.

[@pramodkumar-sc9lv]

the amount of energy that you put into making videos is equal to the ease with which the concepts get into the mind

[@DonkeyLearningIT]

Thanks for your kind comment. I must tell you that I have learned this way of explanation through simple examples from my Indian colleagues while I was studying. By now they all moved back from Germany to India (mostly Bangalore), but I am still grateful for their help when I was a grad student and they were postdocs...

[@fseidenii9636]

Hello, Frederick from United States here... I also find your lecturing to be the most on point on this topic. If I were to offer one point of advice it is to stay on the linear trajectory of how the device will function in simplest terms rather than adding in all the bus stops into complications necessary for each design-methodology. For the most part you are using this method already, so I am only reminding you of what you are already aware of. Good work, rock on.

[@annomaus8386]

Your english is impeccable, and your expoxition of ideas is easy to follow. I am impressed with your grasp of the fundamentals, which comes through in your explanations. I became a licensed radio amateur in 2013 (AB1VL) and this is the most useful presentation of SMPS I have heard by far. The pace is just right for me. Thank you for such a conscientious effort. All the best to you! Chuck

[@abscomm]

Your videos are helping me to FULLY understand how these power supplies function. Do NOT change your presentation it is great.

[@DonkeyLearningIT]

Thanks for the comment. A small portion of the viewers complain that it is too slow. However, I make the series based on the assumption, that some people are just starting out as a repair technician or as a hobbyist. This of course means, that the material need to proceed at a slower pace.

[@dalefirmin5118]

The use of the slide with a block diagram (which includes a picture of a common component for each block) and then showing the location of the same device on an actual circuit board, is absolutely perfect. SMPS are being used in EVERYTHING now--as you mentioned, even those tiny phone chargers.

[@DonkeyLearningIT]

Thanks for the feedback! I did the slides this way, so those people who are just starting out will also have a feeling of how do these devices look in real life. For example, you often see in videos people pointing at the common mode filter, and saying it is "transformer" when in fact it only just looks like a transformer.

[@isaaceguaras]

Not an english native speaker and still understanding what you say, its okay to explain in detail things that are really important to continue. You are making really good videos, thanks.

[@DonkeyLearningIT]

Thanks for your comment! I am not a native English speaker myself, so I am glad that people can still understand what I am mumble in the microphone.

[@xavimangole1153]

You make complex topics easy to digest. Well done! Much appreciated your explanations...

[@gillywild]

I find your presentation exactly right. The level of detail is as you say necessary particularly for the inductors. I look forward very much to the rest of the series. I know this sort of video is not really profitable so I thank you very much for dedicating this time to educating others. I wish health, happiness & prosperity to you and your family.

[@DonkeyLearningIT]

Thanks for your positive feedback. In this&next week I am doing contracting work, so the next video will be uploaded only next Sunday. Regarding profit, I got no advertisements turned on in my channel, so I do not care about number of views/clicks. Main thing is that people learn about the important topics, and that they understand, that after getting the basics, it will be *easy and logical* how to repair or even design SMPS.

[@pedrof.7821]

You are doing an awesome work, appreciate your effort and dedication. I have to be honest, i'm spending a lot of time on learning from your videos. Thank you sir

[@johng8473]

WOW! Just found your videos. I have been self teaching from learned people on you tube. I do not expect to become an expert, but rather an enthused hobbyist. You make understanding the concepts very clear, and easy to comprehend. In the short time I have spent watching your videos, I have connected the dots (so to speak) of every other video I have watched, and have a much better understanding of the principles and concepts of the electronics I have been laboring to understand. THANK YOU SO VERY MUCH..Please keep up the videos, I promise to watch and like every one. You are an exceptional person and an outstanding teacher.

[@DonkeyLearningIT]

Dear John, my idea was exactly to provide videos which are going just deep enough for people to understand what is happening in a switch mode power supply, and what processes take place when energy is transformed. I am glad that you liked the contents, please keep on watching ;) If my health and time allows, I will definitely produce more videos.

[@manaharlotia7233]

Your way of explaining is nice.neither u r fast nor you r slow you are perfect.your presentation is excellent.thanks for video.

[@johnmccloskey5572]

as a beginner somebody learning of electrical you're doing a very good job I'm not that smart of a person but I learned a lot

[@DonkeyLearningIT]

Thanks! That was exactly the intent of this videos, to explain for people the basic ideas. Otherwise there is no way to repair these power supplies, because they are complicated circuits. Watch the other videos in the series, since this is just the entry to the whole story.

[@stevet2892]

+John Mccloskey hey ,if anyone else wants to learn about electronic repair try Saankramer Electronic Magazine System (do a google search ) ? Ive heard some amazing things about it and my m8 got great results with it.

[@kiswahilikitukuzwe2547]

Much respect and appreciation from Kenya for the time, dedication and patience you have put in this wonderful series to impart this invaluable knowledge in such a simplistic and holistic way!!!

[@jackdallwitz5086]

This series of videos has been excellent so far - I've found the pace and level of detail just right. Thanks!

[@renatorobles7440]

Good morning ! one of the most complete very well informative courses over the net, with theoretical and empirical practical explanations nicely explained, Thank you very much ! Gracias !!

[@francismannion7075]

No, I think your presentation is perfect. As a hobbyist I find I am just now starting to understand the role of the inductance in a switch mode power supply.

[@DonkeyLearningIT]

I am glad that I could give some information to you, and that hopefully you learned something from the video. Though, after I get up from my A$$ and finally make new videos in the series, I will have to include some suggestions what people said I should change.

[@mohamedkikia7338]

I've just come across you videos recently and they are excellent and well explained. I repair switched mode power supplies ( a lot of the Peter Chow design) as well as ATX power supplies and some LCD monitor supplies as a hobby. Your videos are well presented and very informative. A person never stops learning! Keep up the good work.

[@jrmiller034]

Your presentation in all forms works for me. I have rebuilt hundreds of different types of power supplies. Watching you videos and hearing your explanation I am learning and understanding so much more that I am sure I will be able to fix more in much less time. Thanks You and please keep making your Videos.

[@DonkeyLearningIT]

Many thanks for taking your time and giving a feedback ;) A large portion of my viewers do not understand, why we are not just jumping deep right into the middle of repair. No matter how many times I repeat, that first we need to go through the basics, after the basics it will be a walk in the park to understand what is going on.

[@enalisemelbye9244]

Thank you so much for your videos. The educational value is very high to me, and I watch them with great interest. I learn so much from them, so big thanks from Denmark.

[@DonkeyLearningIT]

Thanks for watching the contents. I also learn from the feedback and based on that hopefully I will be able to improve the contents and the way how I present things.

[@TanmayvMukim]

your way of explaining inductor back emf was good. It helped me to imagine it quite clearly.

[@bypass666666]

You're doing just fine to answer your question at the end of this video. I already to a certain extent understood inductors but this was nice for a recap, and undoubtedly will be extremely useful for people with none. I've only watched up until this video in the "series" on SMPS however I'm looking forward to watching the rest. Going to subscribe and recommend, thanks for going in depth (not too far) on SMPS. 👍🏻

[@DonkeyLearningIT]

Thanks for the comment. I appreciate it if you recommend the content to others. I must say, I could have done a more clear job on the inductor, and I am afraid that I made it a bit more complex than needed. Now after 7 videos I would probably do the discussion differently. Since KZbin does not allow to change videos after they are uploaded, I will try to be more clear in the new episodes.

[@jeffersononyango8539]

This is by far the most informative tutorial, you have significantly reduced my resesrch and accelerated project. Salute!!!

[@DonkeyLearningIT]

Salute to you too! Thanks for watching!

[@Inspironator]

I think you are providing valuable information that is sufficiently thorough for troubleshooting and repair of SMPSs as well as other circuits. Keep doing it without any changes. This is very good, if not the best on KZbin!

[@DonkeyLearningIT]

Thanks for the positive comment. I would say that there are better videos out there, which go deeper into the topic. However, for people who start out in SMPS after simple analog circuits some of those videos are often way too tough to follow.

[@tomfenn7149]

Excellent series! I know my/this comment is 5 years late, but your pace is just right. Fast? A bit, but you explain so well, and so visually, the slight fast speed doesn't matter. :)

[@beverley8987]

no don't change a thing your vids are great boy does this bring back old memories am about to watch #4 this is great stuff thanks again for your giving such time to us all so much appreciated and becoming a fan of this presentation

[@mitulshah9295]

You are explaining perfectly and can understand properly. Please keep up the good work. Thank you

[@DonkeyLearningIT]

Thanks for writing a comment. I am ashamed that so far I did not manage to upload a new episode, but hopefully soon I will have a bit of free time to work on videos again...

[@matcas4755]

Your communication of these concepts is actually very good ..

[@code7richardson268]

your presentation is perfect, Searching for something like this for awhile and couldn't been a better timing Blessed

[@freelander1794]

Thanks. I am following this series and think you are doing a great job. Your method and presentation are very good and I look forward to the next video.

[@DonkeyLearningIT]

Thanks for the reply, and I am happy that you find the way of presentation OK. To be honest, I am doing it in the way I have wished that it should have been presented for me when I was a student. However, based on some of the comments, I definitely need to dial back on theory, so I have removed all equations which I intended to put into the second video, though they were very basic (like law of induction etc.). I can just quickly explain those without any math as well.

[@user-mx4vs5eb3u]

Thankyou for going through step by step on your Video . I found it easy for me to understand you explaining the functions of each Commponent works than my lecture does.

[@paulmuff9883]

I personally think theses are the best exportation I’ve watch yet you speed etc is that great I can finally follow this type of information , absolutely love it many thanks and carry on👍👍😀

[@SalimAhmad204682]

Very good presentation. Just right not too fast not too slow. I can follow and understand very clearly.

[@MattyEngland]

I love the way you present things. Very easy to understand and learn.

[@DonkeyLearningIT]

I am glad for you comment! Easy learning was the main idea behind the series. Instead of producing something with loud techno music in the background and me pretending to be an expert, I though that it will be useful if I just explain how things work instead ;)

[@steveschaffer4224]

VERY imformative .this if the video beginners need to watch .it lets you see the whole picture then learn spacific stuff later .wish more videos were like this one

[@DonkeyLearningIT]

Many thanks for the comment! Many people thumb the videos down, because they do not understand why I am not just jumping right in the middle of SMPS repair, without realizing, that one must first understand the very basic ideas behind an SMPS.

[@garycourt8593]

Of all the instruction I have had your clarity an presentation rates with the very best, looking foreword to all of all of your series

[@DonkeyLearningIT]

Many thanks man! I try to come up with weird analogies which are as easy to understand as possible. I though that instead of going into complex mathematics, a basic explanation would be enough for most people.

[@joshuastaford1371]

general presentation for my side its real good since it help me to take hints , be blessed sir

[@DonkeyLearningIT]

Thanks for the feedback. I could use some blessing as well, wish it to you too. I think all of us would like to have a better health/life.

[@matthew1333]

Really appreciate your work , the details on everything makes you see the whole picture clearer

[@SVSunnyJim]

Thank you. Your a great teacher and your presentation is clear and on point. Even as a beginner, I am able to follow these concepts. I've subscribed and will be browsing through your other videos. Many thanks

[@alejom.depuch831]

Your videos are very useful but I have an important constructive critic to make: the mechanical analog of an inductor is a mass (hence the inertial effect) and not a spring, which is actually the mechanical analog of a capacitor. Think of it as a car which is going to oppose to the force you apply to move it but once it’s moving it will conserve the energy as inertia.

[@betta67]

Better yet, as a pendulum that once the force is removed starts to move in the opposite direction...

[@909sickle]

Thanks for adding that. That's helps me understand. You should make videos too! This guy is doing a good job so far, but I had trouble imagining the magnetic fields and how they worked from this video.

[@jonathansignori4456]

bien comprendre the very basic ....it a great reminder ...good speed! I so nice to know real personne avec lart d'enseigner !!c'est super mec lache pas ! And thank you for your efforts in doing this it appreciated

[@fareedaramdial7000]

you are doing a fantastic job of explaining...wow love your style

[@benclarke5495]

Just the right speed for me. Very easy to understand.

[@Fanof60s]

Just hit on these video clips yesterday. Perfect way of explaining.

[@DonkeyLearningIT]

Many thanks for the feedback. There is a long way to go, several videos will be still coming up on SMPS fundamentals and repair.

[@annyan904]

eagerly waiting for your next video.... awesome explanation no university explains these things with this clarity.....thanku

[@stevea5407]

Just found you DL. Great videos ! they are just the correct pace for me. And you explain in a very understandable manner not to much maths etc. Well done!!!!!

[@DonkeyLearningIT]

Thanks for the feedback! As I said in the first video of this series, in the university I was force-fed with lots of math, which did not help me at all. Some professors probably have never touched an actual circuit, which is a shame, wheres other professors were really practical and helpful. Now looking back to my university studies which was almost 20 years ago, I do not remember the math at all, but the practical knowledge is stuck in my head until this day.

[@basheerkhan6040]

bravo well explained and very informative for those that are involved in electronic as many electronic devices use switch mode power supplies.

[@sudhirpatil3434]

Your way teaching stu is really appreciated- i have gathered lot of information, n thus knowledge! Thx

[@mpadlite2925]

Thanks for yet another brilliant video!! An I can of course only speak for myself but I believe both the "level" and "tempo" are excellent! Best regards

[@getknowledge450]

Thank you indeed for this nice series. Please keep it on in this manner. It's very useful to have videos on this complex topic in such a detail. I really appreciate it and can't wait for next episode - so once again thanks and have a nice day :)

[@erkmann4398]

Great information. This is what I needed to get more knowledge on power supply repair.

[@DonkeyLearningIT]

I am happy that the video was informative!

[@thisnyper]

Master, your videos are fabulous, fantastic, amazing etc . etc....Thank you

[@sufiyan4973]

Your videos are awesome. Its so helpful. Thank you.. expecting more videos like this.. your method of teaching is helpful👍👍👍

[@mutwakilautodoctorrepairsh2794]

Very Clear and Good explanation thank you for the info..

[@Somesh-Ji]

You are going it in best way... keep going more deep...

[@user-zj1ms4fp5r]

Bravo!!!! finally some one is really teaching/sharing information if you subscribed you will not regret it

[@piehound]

In my opinion your explanation and speed of presentation is OK for the average person without a technical background. But for me personally it's a bit redundant. Since i have some experience with electronic repairs and also knowledge of inductors from my physics courses. Keep up the good work. And thanks much.

[@sudhirpatil3434]

You certainly make complex stuff simple- thx for info!

[@brucewilliams6292]

Thank you for your excellent presentations!

[@mohammedmariff9034]

its very cool way of teaching and explaining .. thanks

[@MrDhanesh2nair]

Good, you are doing a brilliant job. May God bless you.

[@venkatakrishnansrinivasan6928]

Excellent video ! Clear presentation! Good English ! Keep the good work going!

[@kabandajamilu9036]

So nice and educative sir

[@saghirahmad9634]

very nice way of speak non English people can understand easily

[@naziawahid1]

U r so good sir but need a little slow from Pakistan really lov electronics teachers such like u sir Ji thnx

[@hadireg]

greatly explained!! Thank you!!

[@natmannetjie]

excellent professor,your lecture is just right,thank you very much

[@DonkeyLearningIT]

Thanks for the comment! I just uploaded a new episode, and there will be many more coming.

[@SP-kd6iv]

i am grateful to you for the informative videos

[@misbahtabboush9994]

the explanation is very clear and so good

[@DonkeyLearningIT]

Thanks for the feedback. As I usually write, go through the whole series (new videos are coming up soon) to learn more about the SMPS principles before we go into practical repair.

[@AtmaS]

Thank you for a clear presentation. Well done.

[@rightmasterstanleyobi]

This is great, very detailed.. Thanks, much appreciated

[@benjeichan7347]

I appreciate your effort and dedication,thus knowledge! Thx!

[@frankpitochelli6786]

Sir-Qweet.. Love the way he say circuit. Very smart guy.!!

[@DonkeyLearningIT]

Yeaah, I know... But I am just a Donkey, so it's all good ;) In the meantime I have learned to pronounce it almost right, or at least close enough in newer videos.

[@frankpitochelli6786]

@@DonkeyLearningIT....please no offense intended, you are a very smart man and know circuitry. I'm just joking with you about your pronunciations..😉 Keep up the great work.!!

[@DonkeyLearningIT]

@@frankpitochelli6786Do not worry, no offense taken from my side. I call myself the Donkey since I do not mind to learn new things, and in this case I had to learn how to pronounce *circuit* after a couple videos.

[@frankshaw7325]

It’s just perfect the way you present thank you.

[@laphouses3391]

good way of teaching. grate job

[@truth1234ist]

Awsome teacher love it........ it's so nice I cant stop watching.....

[@DonkeyLearningIT]

You still have lots of videos to watch ;) If all goes right, tomorrow I should finally upload a new video on the negative feedback loop in PSUs.

[@ulisesaguilar8079]

good night Sir the videos are good ,very well explained, happy new Year

[@justsean5160]

Excellent videos! Thanks you so much. Love the spring example.

[@DonkeyLearningIT]

Yeah, I could not come up with anything more simple than a spring. Also, once I find somewhere a slinky, I will be able to show why in an inductor the current is being delayed compared the voltage.

[@jaackmcmahon8757]

If you put powered iron on a sheet of paper between/above the energized coil, the powered iron would display the magnetic field as the powered iron is attracted to the magnetic field "lines" of the energized coil.

[@duinnzaiig6493]

Perfectly explained

[@johnmcgiv1]

Excellent in every respect. Many many thanks.

[@DonkeyLearningIT]

Many thanks for watching and commenting!

[@Sebastianstarmer]

Excellent presentation

[@peteruren4086]

You are one of the best!!

[@whoisme678]

Very good presentation. I do think the theory side of it is a little OTT since the majority of the faults are what people can actually see on first examination of the board. When there are no signs, Then the person has to be able to identify whether there is power in and power out. If no power out, how do they trace to find the component which is not functioning. ? Well done.

[@wairarapagates4857]

Perfect, exactly what I wanted to know, thank you.

[@ShahidAhmed-lu8rq]

Hi, you are doing very well, keep it up . I am learning a lot. Thank you.

[@DonkeyLearningIT]

Thanks for the comment. I am glad that some people find the information useful!

[@gmanhvy1699]

great videos short, smart, detailed and simple!

[@abrahamrm5356]

Thanks for the series. I really appreciate it

[@ExplorewithZac]

Really enjoying these videos! My pc PSU is making a very slight buzzing/clicking noise, the power coming from it is not strong, and turns on and off once per second. I am having a very hard time determining what is wrong. I have a spare PSU and I would like to repair the faulty PSU with the part from my spare (also faulty PSU).

[@georgedone7997]

Thank you for the videos. For me the pacing is a bit too slow, I am already familiar with fundamentals as a graduate of a Physics University and looking forward to the practical aspects of designing and repairing a power supply. I kind of liked most the first episode.

[@DonkeyLearningIT]

Thanks for the constructive feedback. The issue is, that most people do not have any university education in electronics, and they would like to do it as either a hobby, or just on the level of a repair technician. As you see, this is a "Catch 22" situation, so I must go through first the basics. Otherwise I fully agree with your comment.

[@NitroGuyJH]

I love your videos! I’ve learned so much and so easily from you!

[@DonkeyLearningIT]

Thanks for you comment. I simply did not come so far to produce new videos in this series because I am so busy with my daily job. However, sooner or later I will put new videos up.

[@ja.935g67]

I think the explanations are great I just think you should say what the component does in a circuit before explaining how it works

[@DonkeyLearningIT]

Hi James. I originally intended this series to repair technicians who already have experience with basic repair, this is why I assumed that they will know how the components work. However, as it turned out later, it is not the case. I will produce a separate series, where I will cover the very basics of electronics, and how components work in a circuit.

[@junieserrano9113]

It's very and good explanation about inductance but my question is how the magnet in the inductance use or help in the power circuit?

[@beauclark2199]

excellent presentations!!

[@antigen4]

i THINK most people watching a video on how to repair swich mode power supplies are VERY WELL versed in the basics of electronics ... maybe skip over component descriptions if i were you??

[@DonkeyLearningIT]

You would be *surprised* on how many hobbyist try to repair SMPS without knowing much of the way they work. For pure repair I think there are good videos out there. To understand those, one of course must know already the basics. However, showing the whole idea before going into practical repair is what is missing for most beginners. This is why I am doing this series. Once I am done with the theory, I will switch over to practice as well.

[@antigen4]

well that's why I'm watching this - hoping for some good diagnostic tips about SMPS repair... I know NOTHING about them really- though I've watched lots of videos and done some reading but I have a pretty good and 'deep' understanding of individual components and what they do, etc. LInear supplies make MUCH more sense to me though... :P

[@antigen4]

the only problem is that you made SIX (6) videos on the topic - the last five of which describe the components but without ever actually talking about any practical repair ...!! :P

[@DonkeyLearningIT]

That is because without the basics there is absolutely no point on trying to go into practical repair. I can just exchange a FET, a driver IC and make a video out of it, and 80% of the people will not get it *why on earth* those parts were exchanged. It is like if you ever looked at Xbox repair. There were guys out there, who claimed the issue is with the position switch, since the switch emitted a rattling noise. However, these guys were not aware of even the very basics, and they did not know, that a gravitational switch has a ball in it, pure and simple. Many people watched those videos, and not knowing better, they spent time and money replacing components which had absolutely nothing to do with the real problem...

[@antigen4]

i always find the most useful such videos - the presenter will explain what they found in their diagnosis - and the conclusion they made and WHY etc ... at least in my opinion. in my own example I studied LCR circuits in high school but also was 'into' electronics when i was very young... so I have a pretty good basis for understanding the parts and how they are made - though for me switch mode power supplies are still pretty confusing - even if i understand all the theory about how they work ... i have a few defective SMPS units and still having a hard time diagnosing them ... :) linear power supplies are much easier :)

[@janermejia555]

I love your videos bro. Keep it up.

[@user-be4yc2vr5c]

Only thing I have to say thus far is thanks again for awesome video an I hope you do like this same deal but for a computer PSU..

[@DonkeyLearningIT]

The main idea is to get to ATX power supplies, since those are worth to repair. However, first I was trying to show the basic principles which apply in any kind of switch mode PSU in general.

[@user-be4yc2vr5c]

Yeah this was a key video for me comrade, since I have like 10 spare ATX style SMPSUs an no actual PSU for myself(poor) so this helped me in truly understanding how not just this powersupply worked and everything, but all SMPSUs, for future PSUs I make. Am looking forward to your recovery and the rest of your detailed videos. You are a great teacher .@@DonkeyLearningIT

[@Vidya1939]

Explained very nicely, following u very well tks

[@frikkiejacobs8858]

This info is awesome. Thank you!