Understanding Electronics Basics #2

[Muttley600]

Here is a youtube video "Scopes for dopes" https://www.youtube.com/watch?v=8ZKMrzTGxLQ&feature=my_favorites&list=FLiqd3GLTluk2s_IBt7p_LjA

There is a lot of noise in the audio, but otherwise it looks good.

Well, this morning has gone quick, found the first part of vid very interesting about scope screen & I can see how it relates to the cartisean plane **broken link removed** then I've just sat through another hour of basically what I already learnt about using scopes, time out as I need to get ready for work & it is just moving onto slopes (which I want to watch) but will have to be tonight or tomorrow now

 

[Muttley600]

Note the arrow is pointing in towards the "gate" terminal (unlike a transistor where it's on the "emitter") and that direction identifies the JFET as an "N" channel Type. Arrow going the other way indicates a "P" channel type.

Morning CBB, you know when you ask a question & then the answer dawns on you anyway, as soon as my head hit the pillow last night, I got it **broken link removed** much the same as I finally got NPN - PNP

Never mind, it is all starting to fall into place, so know I have rest of vid to watch/learn math for triangles & sim still to play with, may be quiet for couple of days until I've absorbed it all inbetween work **broken link removed**

 

[cowboybob]

So what is the other

Both definitions are in the quote. I think, though, I see were the confusion lies:

First 2-D plane:

One is Cartesian which is like the sillyscope and polar coordinates.

Second 2-D plane:

This plane (The other 2-D definition) is a circle. A point on the plane is given by an ordered pair of (p,θ) rather than (x,y). θ is at what angle and p is the length from the center.

My addition.

 

[Muttley600]

Both definitions are in the quote. I think, though, I see were the confusion lies:

Good catch, I was relating them as the same, just that you can only see part of cartisean plane when looking at X/Y

Thought I had it then but I haven't, I'm seeing cartisean plane over wave/slope in fact it seems to measure anything & everything, albeit in different variations

 

[KeepItSimpleStupid]

Polar plane

https://www.wolframalpha.com/input/?i=+polar+coordinates

 

[Muttley600]

So we are still using the cartisean plane to find (for lack of better description) an extension of X-Y & hopefully
I'm guessing here, the degree factor? & length of one side of triangle?

 

[KeepItSimpleStupid]

When you understand the math, Ill need to intruduce the concept of vectors and scalers. Once that is done, we can put L, R and C on a single graph and solve for phase and impeadance at a single frequency.

 

[KeepItSimpleStupid]

CBB:

Try this on the sim: A 100-1000 ohm resistor, a 1 uF capacitor and a 1H inductor all in series. Set the frequency to 1571 Hz and have two traces set up to measure the voltage across the capacitor and the inductor simultaneously. The result should be interesting if I did my calcs right.

If you post it, it could be information overload now, but you should see the "interesting" result. If you don;t see the "interesting" result, I'll have to look over my calcs again.

 

[cowboybob]

Just read the post.

Give me a few and I'll post it on this same one (#29).

OK. This what you're looking for?

(Sweep freq, range is 1Hz to 2kHz, 1V PP sine) with highlighted R changes:

View attachment 62752 View attachment 62753 View attachment 62754

I can see inductor V with a 100ohm R is enormous...

And the notch freq for the cap is consistent (162.5Hz) in all three, but starts to climb for the inductor.

What am I missing?

 

[KeepItSimpleStupid]

No, a single frequency. At that frequency, the voltage across the inductor should cancel the voltage across the capacitor. So, you should get 2 sine wave 180 degrees out of phase as if there was zero capacitance and zero resistance on the circuit.

 

[cowboybob]

I see.

I'll give it another shot.

 

[cowboybob]

OK. Changed circuit, as you'll see.

Still not seeing 180° L to C phase shift.

View attachment 62757

Note on snip indicating "Mode" is in error: Mode is "Normal" (as the scope setup shows).

 

[KeepItSimpleStupid]

You may need two scopes and a little re-arranging.

You need to display VF1-CapV in one trace and CapV-IndV on the other trace.

You can probably do what I need by using:
1. Isolated voltage source
2. Resistor
3. Capacitor (probe at res/cap junction= cha a)
4. Put ground here
5. Connect to inductor
6. connect back to power supply
7. Put other channel at the junction of inductor (cha b) AND THE POWER SUPPLY RETURN

The problem is that channel B has to be inverted. Not sure you can do that.

Anyway, you need two traces with JUST the voltage ACROSS the capacitor and another trace with just the voltage across the inductor.

If you use two scopes, they both have to trigger on the same source.

This is one of those things that could be done with a 4 channel scope so that the resultant channel is a defferential measurement of say A-B and C-D with the trigger being the power supply zero cross.

If you can put the scopes ground in the middle of the cap/resistor junction and you can invert one channel, you can get both Vcap and Vind.

I hope this makes sense. My head is doing it's thing again.

 

[Muttley600]

Glad to see you are keeping yourselves amused while I'm busy, I'm not even going to ask why we have a wave with no frequency.lol
See, I'm learning

Morning KISS

 

[KeepItSimpleStupid]

Morning. It's like 4:20 AM here and I'm not asleep yet. I figure you have a lot to do. Maybe, I need to play with a SIM?

 

[Muttley600]

Morning. It's like 4:20 AM here and I'm not asleep yet. I figure you have a lot to do. Maybe, I need to play with a SIM?

Cool, are you only 4hrs behind us now, my mistake, still looks like 5
Sims are great, CBB found me a link to it, very easy to use, but it'll be buried in one of the threads somewhere, just about to watch last 45 mins of vid
I'm getting there, math next

 

[cowboybob]

Working it...

Sorry your head's at it again, KISS.

 

[Muttley600]

ok, I have just learnt that using Pythagorean theory gives us the length of missing value with triangles, rest will have to wait til later, but I can see where we are heading, need to spend more time on this but basically a triangle is going to add up to 180degrees or 1 radian (half a circle) so it is a way of finding degrees.

Don't bombard me with any more until I get this bit firmly in my head, I'll give you a shout, in the meantime carry on playing **broken link removed**

 

[KeepItSimpleStupid]

That's the plan.

BTW, there are 2*∏ radians in a circle. 1/2 a circle would be ∏ Radians or 180 degrees.

Some useful angles are 0, 30, 45, 90 and 180 degrees. These have a corresponding number of radians. i.e. 90 degrees is [latex]\frac{\pi}{2}[/latex] radians

if the angle is 45 then it's 360/45 is 1/8 of a circle. So it's [latex]\frac{1}{8} \frac{2\pi}{1} = \frac{\pi}{4}[/latex] radians.

See: https://en.wikipedia.org/wiki/Radian

_____

2∏ Radians is an exact number. We might use 6.2831852 or 6.3.

______

Incidently, [latex]\frac{22}{7}[/latex] which equals 3.142857143... is very close to ∏ which is 3.1415926... So, if your trying to compute the circumference of a circle and you don't have a calculator handy, [latex]\frac{22}{7}[/latex] may be close enough for the value of ∏.

 

[cowboybob]

No, a single frequency. At that frequency, the voltage across the inductor should cancel the voltage across the capacitor. So, you should get 2 sine wave 180 degrees out of phase as if there was zero capacitance and zero resistance on the circuit.

KISS,

Try this. I might note that ANY scope presentation shows both VF1 & 2 in sync. Also, I have no way to invert a trace (channel) on the sim scope(s).

I will say the sweep method at least shows the V-gain of the cap as going to zero (just not exactly zero) ((and the inductor rising about 1.18V, then settling back to 1.0V) at 1.57kHz and higher.

**broken link removed**

Anyway...