Understanding Electronics Basics #1

[Muttley600]

Keep in mind, Graham, that for the most part, this is all an exercise to explain the difference between the peak AC level(s) you see on a scope and what a multimeter will display as an AC voltage level. With a Sine Wave ONLY:

I know, I just want to make sure my understanding is 100% firm, accepted it is only for a sine wave **broken link removed**

ok, lets try & realte to this formula, the numbers aren't important but the process is what I'm trying to see & the numbers should give me that process
View attachment 61914

If the Peak to Peak value (from the scope) is 3.84VAC

Vpeak

then the 0 to Peak is 1/2 that, or 1.92.

This is the divide line between Vpeak & square root symbol

Multiply 1.92VAC times 0.70711

So this must be the square root symbol but is not actually relating to square root on this occasion, how confusing is that for a beginner **broken link removed**

and you'll get the 1.357VAC RMS value.

This is the Vrms =

& the sad part, I still don't think I've understood it correctly **broken link removed**

Multiplying ANY 0 to peak AC voltage level by 0.707 will give you the RMS value that you will see on most multimeters, sim or real.

See, now I have noted that, that is real world useful information **broken link removed**

I got the sim multimeter to behave in the three sims below.

Is that because you changed the battery for a function generator

I should add that I generally limit my use of a multimeter in circuits of this type to DC and resistive values. For all AC work I use a scope.

Makes sense, but what happens when we have things like we are working on, still scope **broken link removed**

 

[cowboybob]

Here ya go:

[latex]Vrms=\frac{Vpeak}{\sqrt{2}}[/latex]

where [latex]{Vpeak}[/latex] is the 0 (zero) to peak VAC value. In this case 1.92VAC (1/2 of 3.84)

The [latex]{\sqrt{2}}[/latex] is a constant, in the case, 1.414. This value never changes, no matter what happens in the rest of the equation.

so,

[latex]Vrms=\frac{Vpeak}{1.414}[/latex]

Thus, [latex]\frac{1}{1.414}=0.707[/latex].

Finally, in this case [latex]Vrms=0.707 * 1.92=1.357[/latex] RMS VAC

 

[Muttley600]

Morning CBB

where [latex]{Vpeak}[/latex] is the 0 (zero) to peak VAC value. In this case 1.92VAC (1/2 of 3.84)

Thank you, so when anyone talks about Vpeak they simply mean 0-P

The [latex]{\sqrt{2}}[/latex] is a constant, in the case, 1.414. This value never changes, no matter what happens in the rest of the equation.

So squiggly tick can stand for a number of things, but I can relate this number to transferring multimeter readings to scope - always but has that number simply there because it is a rule or because you've calculated it from this fromula? then squared it

Thus, [latex]\frac{1}{1.414}=0.707[/latex].

Lost me, I can see how 1 divided by 1.414 gives you 0.707 but I can't see why 1.92 0-P has turned into a 1 all of a sudden

Finally, in this case [latex]Vrms=0.707 * 1.92=1.357[/latex] RMS VAC

There isn't a short cut to this is there, I'm gonna have to learn how to do it properly

So whats my best route forward, to me it looks like I need to finish learning algebra then calculus before even attempting any of the different laws if that makes sense?

ok, Instead of learning new things I've been busy making new notes on what we have covered so far so we don't end up repeating anything
(so far I've got to page 8 on this thread - note to self as reminder, then need to double back over DC thread to pick out anything I've missed)

It's amazing how much I've actually learnt without the math, a credit to you both

 

[Jony130]

Look her to see what peak is

http://www.kpsec.freeuk.com/acdc.htm

http://www.learnabout-electronics.org/ac_theory/ac_waves02.php

"Peak voltage is another name for amplitude"

 

[cowboybob]

Thank you, so when anyone talks about Vpeak they simply mean 0-P

Yes.

So squiggly tick can stand for a number of things

No. the [latex]\sqrt{x}[/latex] symbol only stands for the "Square Root" of x, in this case ("x" is often used to indicate an "unknown" number, that is, unknown only until you solve the equation). In our case x is always equal to 2.

On your calculator there is often a sqrt button. If you plug in a number and then hit the "sqrt" button, the calculator will display the "square root" of that number. Try it.

but has that number simply there because it is a rule or because you've calculated it from this fromula? then squared it.

It is a rule. The formula always has that value in that spot.

Lost me, I can see how 1 divided by 1.414 gives you 0.707 but I can't see why 1.92 0-P has turned into a 1 all of a sudden

Let's think of the formula: [latex]Vrms=\frac{Vpeak}{\sqrt{2}}[/latex], as [latex]Vrms=\frac{1}{\sqrt{2}}*Vpeak[/latex] (they are the same formula, just opened up a little).

So the formula, with all its numbers, would look like this: [latex]Vrms=\frac{1}{1.414}}*1.92[/latex] which then becomes [latex]Vrms=0.707*1.92[/latex].

Thus [latex]Vrms=1.357[/latex]

There isn't a short cut to this is there, I'm gonna have to learn how to do it properly

Well, hopefully, I've made it a little clearer. But, yes, there are no shortcuts.

But remember, the Vrms = 0.707 * Vpeak is what you should remember. How we got there is interesting, but not essential to getting the answer(s) that we're looking for.

Finally,

Is that because you changed the battery for a function generator

For the demo circuit, Yes. I'm still not sure why the multimeter is misbehaving in the oscillator circuit. I'm gonna have to ask the TINA people what I'm doing wrong, or not doing right. The help screens are singularly UN-helpful...

 

[Muttley600]

"Peak voltage is another name for amplitude"

doh......I know CBB will forgive me but KISS is gonna kick me, I don't know how I've managed to get confused **broken link removed** because I'm sure we've covered it but I've been mistaking P-P as amplitude, hence the reason for me now making folder of the basics so I don't get tripped up again, yesterday set alarm bells ringing that I'd started to forget stuff when redoing rms which was also covered I think

Sorry guys

 

[Muttley600]

No. the [latex]\sqrt{x}[/latex] symbol only stands for the "Square Root" of x, in this case

ok, as long as it isn't cubed with a 3 the other side of the tick

("x" is often used to indicate an "unknown" number, that is, unknown only until you solve the equation). In our case x is always equal to 2.

Thank you

On your calculator there is often a sqrt button. If you plug in a number and then hit the "sqrt" button, the calculator will display the "square root" of that number. Try it.

ok, now your really going to think I'm thick, square root means 'power of two'

do you know that really works, how clever is that, I really understand something **broken link removed** might not be much to you guys but thats ace, it IS starting to sink in **broken link removed**

It is a rule. The formula always has that value in that spot.

Rules are good

Let's think of the formula: [latex]Vrms=\frac{Vpeak}{\sqrt{2}}[/latex], as [latex]Vrms=\frac{1}{\sqrt{2}}*Vpeak[/latex] (they are the same formula, just opened up a little).

So the formula, with all its numbers, would look like this: [latex]Vrms=\frac{1}{1.414}}*1.92[/latex] which then becomes [latex]Vrms=0.707*1.92[/latex].

Thus [latex]Vrms=1.357[/latex]

ok, don't give up on me I'm nearly there, I can see Vpeak/Vrms & even how the square root works to 1.414 & is then didvided by one

But where did the 1 & the multiplying come from, I can see how it's working out but I'm not understanding how we got there, this is because I haven't covered 'what is this called'

Well, hopefully, I've made it a little clearer. But, yes, there are no shortcuts.

Fair enough, I'd already come to the conclusion I need to learn more, I'm guessing as I can't relate to anything but the basic in this, I'm a long way off yet but thank you for seeing my struggles & helping me through, it means a lot, this may only be a hobby for me but it's still great fun learning

But remember, the Vrms = 0.707 * Vpeak is what you should remember. How we got there is interesting, but not essential to getting the answer(s) that we're looking for.

Noted, thanks

For the demo circuit, Yes. I'm still not sure why the multimeter is misbehaving in the oscillator circuit. I'm gonna have to ask the TINA people what I'm doing wrong, or not doing right. The help screens are singularly UN-helpful...

Still a great program though, it has helped a lot **broken link removed**

Had to come back into computer to reply as out playing with bike, just plumbing new radio in as last one now waiting for repair in about * yrs time when I understand electrics **broken link removed** got a day out for comms check before going abroad next time I'm off, so, yes, I'm cutting another ciggy plug off but this time it is not realient on one of those mini pcb thingys so should be fine with bullet connectors through fused relay

& KISS couldn't understand me not getting a derivitive **broken link removed** Now I've got to go over it again to put into folder (thankfully he linked to a kids program that explained it in english **broken link removed**)

 

[KeepItSimpleStupid]

No wonder your confused: https://en.wikipedia.org/wiki/Amplitude

I never used the word amplitude, just p-p, 0-p and RMS. In a sense the wikipedia article is right. It's a number that describes the amplitude. By knowing the shape (sine wave) and one of those "amplitudes", we can draw the wave.

The sqrt(2) is what they call an irrational number. It cannot be written as a ratio of 2 integers. 1.414 is close enough to use for our purposes.

When I learned math, I learned something called prime factorization. A number is prime when it's only divisable by itself and 1. I think 1 is prime. So, 1,3,5,7,11,13,17,19... are prime numbers.

We learned simple things like 25 = 5* 5; This also means the sqrt(25) = 5

30 = 5 * 2 * 3
60 = 2 * 2 * 3 * 5

I'm not sure why I'm bringing this concept up.

the sqrt(2) we said is 1.414, so 1.414*1.414 = 1.999396 which doesn't quite = 2

If we use more digits and multiply 1.414213562 * 1.414213562 we get closer to 2 or 1.999999999
but it still isn't 2. Only the sqrt(2)*sqrt(2) is exactly equal to 2.

A power of 2 is
2^0, 2^1, 2^2, 2^3
or 1, 2, 4, 8, 16, 32, 64, 128

A power of 10 is
1, 10, 100, 1000, 10000 etc.

Sqrt means that two of some number multipled together equal that number.
A cubed root means that 3 of the same numbers multipled together equal the number.
So, the cube root of 27 = 3 * 3 * 3 is 3.

 

[cowboybob]

But where did the 1 & the multiplying come from, I can see how it's working out but I'm not understanding how we got there, this is because I haven't covered 'what is this called'

OK. Consider this:

One times anything changes nothing.

For instance: [latex]\frac{10}{2}=5[/latex], right?

This could also be written: [latex]\frac{1}{2}*10=5[/latex]. Still the same answer.

Two ways of looking at the same formula.

[latex]\frac{10}{2}=5[/latex] is a simplified version of [latex]\frac{1}{2}*10=5[/latex]

Using words, the first formula reads: "ten divided by two equals five"

The second formula reads:" one half times ten equals five".

 

[Muttley600]

No wonder your confused: https://en.wikipedia.org/wiki/Amplitude

& guess where I've been getting my info, at least that doesn't make me totally mad, ok, the word amplitude is banned unless accompied by the definition **broken link removed**

It cannot be written as a ratio of 2 integers.

I might need to know what integers means **broken link removed**

When I learned math, I learned something called prime factorization. A number is prime when it's only divisable by itself and 1. I think 1 is prime. So, 1,3,5,7,11,13,17,19... are prime numbers.

Ok, duly noted thanks **broken link removed**

I'm not sure why I'm bringing this concept up.

Glad you did, can you see why I'm struggling now

the sqrt(2) we said is 1.414, so 1.414*1.414 = 1.999396 which doesn't quite = 2

If we use more digits and multiply 1.414213562 * 1.414213562 we get closer to 2 or 1.999999999
but it still isn't 2. Only the sqrt(2)*sqrt(2) is exactly equal to 2.

Your right you know, of course I didn't check.......ok. I lied, I did **broken link removed**

A power of 2 is
2^0, 2^1, 2^2, 2^3
or 1, 2, 4, 8, 16, 32, 64, 128

A power of 10 is
1, 10, 100, 1000, 10000 etc.

Sqrt means that two of some number multipled together equal that number.
A cubed root means that 3 of the same numbers multipled together equal the number.
So, the cube root of 27 = 3 * 3 * 3 is 3.

You'll be pleased to know I have covered 'the power of' way back, some time long ago.......was it tuesday **broken link removed**

 

[Muttley600]

Two ways of looking at the same formula.

Using words, the first formula reads: "ten divided by two equals five"

The second formula reads:" one half times ten equals five".

But what your saying is contradicting itself, your saying they are the same then giving different definitions of the same thing **broken link removed**

I know they are giving the same answer but they are two different formulas aren't they?

I'm obviously missing something really basic here aren't I

I watched video that said a multiplication was undone by division & vice versa & that made sense to what it related to & I can see your showing me the same thing really aren't you

I need to watch vid again to relate to it **broken link removed**

So order of operation

View attachment 61919

Then we are on about this

View attachment 61920

which is showing a X or / eliminate each other, just gotta get my head around what your showing me now

Edit: so you are showing me you are undoing the division by multiplication but of the top not the bottom, so by my reckoning if I'm learning basic algebra at the moment this is going to come up further down my learning route that you can replace the top number with a one, have I understood that right

 

[MrAl]

Hi,

I see the word "amplitude" has been kicked around a little in this thread.
That can be a little tricky word, because we can have amplitude expressed in any of:
1. Volts Peak
2. Volts RMS
3. Volts Peak to Peak
4. Volts Average

The amplitude of a sine wave is usually taken to be the peak in pure mathematics, but in electronics we find it used for sine waves in either of the above forms not just peak.

 

[Muttley600]

Thanks for that MrAl, got that bit drummed in

Off out for meal tonight & fencing at some point tomorrow if they deliver as promised, the joys of working & owning your place, spending your hard earned forever looking after it.....sigh
They don't tell you that when you get a mortgage, I had to laugh when I questioned we'd end up paying double what we borrowed & they just said 'oh, don't worry about that, it's just how it is'
Makes me think renting would be cheaper as you don't have to maintain it.lol

Have a good evening everyone

 

[cowboybob]

One times anything changes nothing.

I should have added; "Anything divided by one changes nothing".

AND; "Anything multiplied by [latex]\frac{1}{1}[/latex] changes nothing"

So, [latex]\frac{Vpeak}{\sqrt{2}}=\frac{1}{1}*\frac{Vpeak}{\sqrt{2}}[/latex]: no values in the equation been changed.

We can move values around: [latex]\frac{Vpeak}{\sqrt{2}}=\frac{Vpeak}{1}*\frac{1}{\sqrt{2}}[/latex]: again, no values in the equation been changed.

Or: [latex]\frac{Vpeak}{\sqrt{2}}=\frac{1}{\sqrt{2}}*\frac{Vpeak}{1}[/latex]: and once more, no values in the equation been changed.

But we're left with two distinct operations that can then be multiplied together.

We are not replacing Vpeak with 1, we are multipling [latex]\frac{Vpeak}{1}}[/latex] by the fraction [latex]\frac{1}{\sqrt{2}}[/latex].

 

[Muttley600]

Back from pub being the big drinker I am.lol
3 pints & a curry = 1 happy Graham
See I understand that equation *grin*

Let's get my head round last reply

 

[Muttley600]

CBB, are you saying you can break a equation into two pieces by adding one then times equation?
How do you know when to do this?
I can see where your coming from & how it works, but how do you know to do this

What I'm really asking, is what have you learnt that I have not that brings you to this, yes, what your saying makes perfect sense even with my basic understanding

I understand a / can be undone by a x

After staring at it for few minutes, all above have one thing in common, your undoing the division on every one, should I take this as a rule from now on?

 

[cowboybob]

After staring at it for few minutes, all above have one thing in common, your undoing the division on every one, should I take this as a rule from now on?

Only if you wish or need to.

And not so much as "undoing" as breaking into pieces to more easily show the process, of arriving at a solution.

So long as anything you do to the top (the numerator) of an function (division, in this case), you must also do equally to the bottom (the denominator). That's all the rule is.

It's not any different, conceptually, than the example you gave in post #231. You added 3 to both sides of the equation (perfectly legal) and then did the math and then you multiplied both sides of the equation by 7 (also perfectly legal) in order to solve the sucker.

You changed BOTH sides of the the equation (at the same time) in order to solve it.

Sometimes this is necessary in order to keep the various parts of the math problem straight.

 

[Muttley600]

Unfortunately I can't take credit for that, it was a video for teaching kids, but I'm also using it to learn but I get what your saying
Thanks for helping with this, at least it is making sense now

Goodnight all

 

[KeepItSimpleStupid]

Even a fraction such as this [latex]\frac{x^{2}+2x+1}{x^{2}+2x+1}[/latex] is equal to 1.

The error is this thing: (X^2+2x+1)/(X^2+2x+1)

 

[cowboybob]

Did the same thing to me. Too complex? If so, that's kind of lame...

Course, it's free.

Noticed it breaks as soon as you enter a number or an unknown into a function.

With NO function selected, a number will display, but then enter a function and it breaks.

Danger, Will Robinson...