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enewton
modified 6 years ago

V over Constant current at cap
4
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02:17:45
A constant 1ma is applied to a capacitor of 1 uf. The voltage required to maintain this current increases over time. This is because the more +q which accumulates on one plate, the more the additional charge is repelled. For more mathematically minded individuals, see the equation for capacitance. C ( farads) = q (coulombs) / V (volts) Rearrange this equation to see that V = q / C. Meaning the voltage is proportional to the amount of charge stored and inversely proportional to the capacitance. This current is 0.001 C /s, so the voltage goes up to 1000 V after 1s. (0.001 C/0.000001 F) = 1000 V
published 6 years ago
enewton
6 years ago
@2ctiby
2ctiby
6 years ago
@enewton ... Using a 'final' standard equation is fine to get us where we want to go, and so gives us a result. When we do that, we usually have to be content to accept various phrases, such as "the voltage increases in a linear way" etc. If however, we wish to explore, understand and mathematically describe and demonstrate such a phrase, then we probably need to delve deeper, perhaps by using calculus. For instance, the speed of a car for a journey can be given by distance/time taken, but if we wish to know the speed at a particular point of that journey, then closer examination is needed.
2ctiby
6 years ago
@enewton ... In your presentation above, Q =CV and  Q = it  could be combined to give CV = it  ... that could then be re-arranged to give:  i = CV/t .... and then we could start to think in terms of instant events rather than that general formula, and so arrive at the well known equation:  i = CdV/dt ... Notice there how the  i  represents the current at any specific point in time, as per the rate of change of V ... We could then work from there to find V at any instant (by integrating both sides of that equation to get rid of the derivative there at V). In the case of your constant current we would then see that a linear result would ensue for V, and so we would have described it mathematically and so understood the nature of the phrase  "the voltage increases in a linear way" as described above ... We would also have discovered, and then be able to mathematically show, that "a capacitor thus integrates constant current" ...  rather than just repeating that phrase having seen it in books/web pages.
2ctiby
6 years ago
@enewton ... What it amounts to with calculus is this: With a basic knowledge of calculus, we can develop an idea with a constructive goal of achieving a result,  instead of simply following a pre-known equation where the algebra letters are simply replaced by known values. The final outcome may in fact be the same result as for popular known concepts with a familiar "final result", but the depth of understanding of those concepts via calculus is at a different level for those same results ... That is why you are likely to see calculus descriptions on electronic websites ... they are an attempt to describe concepts which may be difficult or even impossible to describe without the calculus detail.... it does not necessarily mean that someone who can appreciate calculus has any advantage for practical breadboard applications, but it is "strings to your bow" if you wish to develop in all areas of electronics.
Robert_Kidd
6 years ago
Very clearly explained my friend.
2ctiby
6 years ago
Thanks Robert. Very basic calculus principles are all we need for getting by on EC and on many websites regarding caps etc. I think that many people may be put off by seeing complicated looking symbols and maths sites that delve in to rules which are not generally needed for EC users. I'm still toying with the idea of presenting some very basic helpful guidelines for interested users.
kiani
6 years ago
@2ctibe. I remembet when i mentioned cv=it. You said to me that it was wrong, and i was wrong.. I proved that i was not wrong,, you never said anything, but now it seems you acept that i was not wring and in fact cv=it,.. Good to see we can alk learn,,, i did not nerd your affirmation, but a lot of people might have been mislead.... Try keep out emotions out of your equations.
kiani
6 years ago
@rib_kid you did not understsnd a word of all that,, what a prostitute you are... If you did and do unerstand,, it is possibke to sammrise all that in 3 lines of maths, and 3 sentences.. Lets see you do that.., gi on prove you are notca fool,, here is your chance to show everyine you are not an idiot.
Robert_Kidd
6 years ago
Kiani, you continually show you are a fool by your stupid comments and incomprehensible language.
Robert_Kidd
6 years ago
2ctiby, I’m sure some would welcome that introduction and others might see it as a refresher.
kiani
6 years ago
@rob_ddork what did you not understand.... The english clear enough,, is your mind cleat.enough!? You ate not using, god forbid are you, now!? Read again and twice more until you get it,... you can't do it, cause you did not and do not understand anything..mr. Blob boulait. Rob-dd.
kiani
6 years ago
@rob_kidd you are actually a dik head,, i love maths, all of maths.. And nobody devalued 2ctiby's work here, and never did i say it was nit welcomed. You are evil. I was asking you ti deminstrste that yiu understand, snd yiu are trying ti get out if it by diversion,, yiu are really just an idiot.. And yiu din't know the 1st. Letter if msths or electrinics..... Alsi yiu were denigerating @2ctiby. By trying ti comfort him reassuring him,, he is nit stupid nor a child yiu evil 😈 baskard.
2ctiby
6 years ago
@kiani ... Can you supply the link to where I said that cv=it was wrong please?... I doubt that I said that.
2ctiby
6 years ago
In other words, you can not support your claim there.
kiani
6 years ago
@2ctiby here is your comment to me, in another link...... @kiani ... There is a difference between a formula being correct, and a formula being relevant. The hurz formula there is correct but irrelevant regarding the timing calculation of a capacitor, unlike your formula above (C * V = i * t) which is just plain incorrect
2ctiby
6 years ago
@kiani ... no need for many repetitions ... some of us only visit this site periodically, we are not all glued to it permanently. Can you please give me the link so that I can read what was being discussed in perspective?
kiani
6 years ago
@2ctiby's Quote "The hurz formula there is correct but irrelevant regarding the timing calculation of a capacitor, unlike your formula above (C * V = i * t) which is just plain incorrect"..
kiani
6 years ago
Plain incorrect, dies not have context,. Or does it.. And it is no longer a claim that i made,, right!? So i can support my claim,, hmmm!?
kiani
6 years ago
Shall look for link..
2ctiby
6 years ago
@kiani ... I must apologise to you. It should have read "just irrelevant" there instead of "just plain incorrect". The discussion at that time was about the relevance of i vs di and t vs dt etc. I placed the wrong word there...sorry. For interest sake, when it comes to finding i at a point in time, then my top replies to enewton above here clarify the situation ... ie i = CdV/dt ... ( sticking with i = CV/t would be irrelevant for finding i at each instant of time)....'incorrect usage' was meant rather than 'incorrect formula', but I did not make that distinction properly.
kiani
6 years ago
Nothing to be sorry nor an appology was my aim....it is just that maths. Has different overview than electronics (specially practical electronics). About dv/dt. If the curve is linear, delta can be as big as the entire range if the limits. Then delta can be omitted all together.. This is not dine in maths, cause no need, but in electronic, for quick visual calculations done just by looking at waveforms, this can be done intuitively. Intuitive maths. Does not exist, (yet). That is what makes us humans.... Here is the link anyhow......http://everycircuit.com/circuit/5874316097617920
2ctiby
6 years ago
@kiani ... For a linear dV/dt slope the d parts be ignored in practise, because the V/t conforms to the same theory (being constant throughout), but the d parts can not ignored for a non-linear slope as in RC network cap charging. Ignoring the d and so using the simple 'final formula' therefore works fine eg for a constant current source, but the whole idea of this thread to enewton is that the depth of understanding these things comes via the learning of calculus. Without the calculus, viewers are likely to be mystified by this discussion ... and hence my toying with the idea of presenting a basic calculus guide for EC users with a view to removing that mystery for them.
kiani
6 years ago
Anything more than 3 to 5 lines of maths. Is lost. Similarly anything written longer than 2/3 of A4 sheet, on paper, and perhsps one paragraph, on electronic comm. Again is lost.....people flick through and find short chuncks to read. That is the average bite size.... It takes a bit of thinking how to disguise calculus or maths in electronics and show it electronically with Leds prefebly,,,, otherwise no one will take notice,, if you do a 555 flashing Led you get 300 viewrs, if you do an amplifier you get 20 viewrs... New ways making games, eg. Fladh rate of an Led, (d.flash/dt). But hidden in capacitor discharge,,, , its EC people are interested in flashing lights,. And seeing things happen.. Its taugh to get people to find the connection between maths and reslity. Thats why most people say they hate maths. Cause the link is missing.
2ctiby
6 years ago
@kiani ... yes, that seems to be true. I have this silly idea that perhaps the maths barrier can be broken down for at least some viewers ... it might be worth a try one day.
2ctiby
6 years ago
It would perhaps have to start, not by maths, but with a reaching out towards friendship with a push of humility from all participants in a combined effort to renew a happy structure on EC?
kiani
6 years ago
I don't know i don't agree with yiu.. I am not looking for happiness on EC. When i publish a circuit, i want to be my work criticised as harsh as pissible,, by someone who knows, the thing is if i can not understand in depth, the critique becomes a personal matter. If i am honest at that moment all i need ti say is to be honest and say sorry that is out of my depth, i will have to look into it,,... Humility comes when i stand to argue and bullshitting not to accept i am out of my depth..
2ctiby
6 years ago
So if some want peace and friendship on EC, and others want harshness, then the peace seekers are doomed for a hard time and may be better off leaving the squabblers to continue amongst themselves.... perhaps that is why most of the regulars do no presentations anymore and why EC is such a sad site now..? Perhaps worth some thought.
kiani
6 years ago
Rewrite... What is the ideal.. What is possible. .. What is achievable....... Three questions...........
lenzrulz
6 years ago
Thank you 2ctiby, very well laid out and explained...👍
kiani
6 years ago
Whining, troll charlatan, perjurer, lenzul, confession, he does not respect..
kiani
6 years ago
Huh
hurz
6 years ago
must be frustrating for @2cent to know Lenny does not have a clue what hes talking about
2ctiby
6 years ago
@hurz ... You mock and criticise others who seem to have less knowledge than you, but you are oblivious to some who are shaking their heads at your lack of technical ability in some areas of electronics. They prefer not to mock and gloat as you do, and they know that you prefer to deceive yourself and rant rather than be told things .... so they stay quietly away. ... Concentrate on your own inadequacies instead of persecuting others.
lenzrulz
6 years ago
Well said @2ctiby...👍
kiani
6 years ago
@2ctiby. You are somebody who knows, maths, and s/o who can get his head together to do technical stuff...,, where as lrnzul is just a troll, with NO knowledge of technicals.....you are comparing yourself with him and put yourself on troll list by using this situation to make a point...
kiani
6 years ago
@2ctiby. Lenzul is unable to talk anything technical.. You can make your arguments based on technical matters,,. If a discussion about a technical matter turns bitter, is different to arguing with A charlatan builder who has made a mess if your patio and taken your money... Now i suggest you stick to your calculus snd FET s. And if argument breaks out. At least there will be science in progress eventhiugh it is in the background.....lenzul is a twitter, here for likes. That is nothing ti di with you..
kiani
6 years ago
.
kiani
6 years ago
=
2ctiby
6 years ago
@kiani ... Your unkind comments on the recent lenzrulz presentation of fading LED's were unnecessary and technically inferior ... so you are not in a position to criticise his 'technical inferior presentation' regarding a  Mosfet circuit. You would be better off aiming for kindness, since your non-technical assertions may backfire on you.
kiani
6 years ago
@2ctiby. I have explained it all for you on his post, if you kindly read it,,, if i may say so i think now you hold a grudge against us cause i pointed iut your mistake on cv=it,, it was a bad mistake you made being so technically kind.
2ctiby
6 years ago
@kiani ... stick to technical discussion only, like hurz directed you to do .... you are telling lenzrulz that his setup is wrong, but you do not understand the workings of a nmos, so your opinion there is invalid.
2ctiby
6 years ago
@kiani ... cv = it is only valid for a fixed condition. Your condition was not appropriate, you need to have used CdV = i dt ... That is why you were wrong, and how I clarified that later ... you are lacking in understanding the difference there it seems.
kiani
6 years ago
CdV = i dt. Is wrong. You can not split dV from dt like that..
kiani
6 years ago
Putting different color LEDs in parallel, =,bad idea.
2ctiby
6 years ago
@kiani ... This is why I suggested a short calculus introduction for EC users ... you would then know what I am talking about ... but it met with a determined antagonism if you remember. This is not the place to explain in detail, but just note this: you are saying here that i = CdV/dt is wrong .... I am saying that it is correct ... Now look it up on many internet sites, and you will see that it is correct. The very fact that you do not understand that, is a serious problem which you need to confront before talking calculus any further. You obviously do not know which parts can validly be cross multiplied etc.... if you knew the reasoning, then you would not even be discussing this.
2ctiby
6 years ago
@kiani ... the voltage differences for different coloured LED's does not necessarily play a significant part in a circuit eg where dimming occurs etc. as the voltage changes gradually at the Mosfet gate/ and ds
kiani
6 years ago
No cdv/dt is not wrong, but spliting them like you did,, taking dt as something seoarate to the other side of equation is wrong... the LED just go to the editor and physically change the voltage of green led to 1.8 volt and see what happens.. The light up at different voltages,, a
kiani
6 years ago
In general it is not good idea to parallel diodes or leds.. As you wouldn't do that with batteries...
kiani
6 years ago
That is what dioes are tiny voltage sources, of ~ 0.7 volts,, that is why one needs to overcome that to make current flow..0.7 v being the junction voltage, not available at the terminals.
hurz
6 years ago
@2cent, you talking nonsense, this problem has nothing todo with the driving transistor. Just take two different colored LEDs and drive them in parallel and you will fail.
2ctiby
6 years ago
@kiani ... you are demonstrating here that you do not know how to manipulate sections in calculus.... eg to integrate current with a capacitor from that formula etc. Saying that my calculus statement there is wrong only shows up you lack of usage and lack of ability to learn. If you were to integrate the current there, you would inevitably find yourself cross multiplying sections which I have described here.
2ctiby
6 years ago
@kiani ... It is not necessarily the best idea to parallel LEDs, but it can be done, and it does not warrant too much criticism in various applications.
2ctiby
6 years ago
@hurz ... Two LEDs in parallel will not fail if the mutual voltage is low enough to support them. The EC settings are defaulted to the same voltage.
kiani
6 years ago
It does,, and i,, "I" finished the total of calculus when 9 years old..... Plus trigonometry, plus algebras,... So i know a little.
kiani
6 years ago
It is not allowed, to split up dt from what it is integrally part of, to the other side of the equilibrium.. This might seem ok, ,, and might even give results.. But you run into deep trouble when you try to get it back, cause you lose info. Bad practice in calculus.
2ctiby
6 years ago
Like I said ... try integrating the current there and you will see that cross multiplication is necessary... you obviously do not know how to perform that, otherwise you would not be questioning it.
kiani
6 years ago
Why not show us, in a new post for this,
2ctiby
6 years ago
@kiani ... there is no trouble "getting it back" when the calculus is performed properly with correct structure. Your difficulty stems from a lack of structural understanding.
2ctiby
6 years ago
I have said for months that I am willing to do just that ... but not if it becomes a base for antagonism.... which you have already started. If however, you wish to try your hand at integrating the current from that formula i = CdV/dt, line by line, then I will help you when you are stuck at each point.
kiani
6 years ago
What might look like cross multiplication. Is for ease of manipulation,, but iy really isn't a valid thing to do on its own.
2ctiby
6 years ago
Is that your way of saying that you are unable to integrate that current and therefore cannot obtain a result for the Voltage across a cap at any instant of time?
kiani
6 years ago
No
2ctiby
6 years ago
If you are going to use calculus to do that sort of thing, then you will need to be able to manipulate any necessary parts of a formula as appropriate in order to achieve the required outcome. It is no use saying that "it can not be cross multiplied blah blah."
lenzrulz
6 years ago
Hypocrite, your failure at grasping fundamental calculus is embarrassingly obvious, get a grip on your own technical knowledge before making insinuations about someone else lacking technical knowledge...😡
kiani
6 years ago
@2ctiby. dv/dt is one quantity. Slope.. What is dt, !? Without dv !? inseparable.... But for manipulation we might do it,, but knowing that it is a manipulstion trick to help less thinking,,,, lets see. Say. We have Ldi/dt = cdv/dt could you say. Ldidt =cdvdt.?! Cross mutiplying!?
kiani
6 years ago
Then dt s cancell wr end up with Ldi = Cdv. So. di = cdv/L,, nonsense.
2ctiby
6 years ago
@kiani ... You need to start and continue with good structure in order to avoid unnecessary problems. Look here at your starting point: Ldi/dt ... that represents V (ie: V=Ldi/dt for an inductor). Then look at your next part: CdV/dt ... that represents i (ie: i=CdV/dt for a capacitor) ... so you are starting here by saying that V = i ... we can derive that by cross multiplying as you suggested and then integrating ... but that result does not get us anywhere useful ... there was no structure to your aim. I may start a new thread so that you and others who may be interested can follow a bit at a time carefully with structure ... but I make no promises if one and all are not ready to put antagonism behind and start afresh.
kiani
6 years ago
A theory can be attacked and defended,,, that is healthy,,, you csll it antagonism,,,, mathematical facts can be challenged too,,, it took a long time for earth to be round.
lenzrulz
6 years ago
Defamatory, denigrating and condescending comments are not conducive nor necessary when having an intellectual discussion.
kiani
6 years ago
Charlatan talk.
lenzrulz
6 years ago
Lol...😂

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