# Understanding Electronics Basics #2

Discussion in 'General Electronics Chat' started by cowboybob, Mar 26, 2012.

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2. ### Muttley600New Member

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20^2 = 400 or in log10 8.00000*0.30103 = 2.40824

is this how they are getting base e in log2 (e) ignoring the numbers as they are different

ok, thats a bit more interesting, 10^1 = 10 or in log10 (I don't know if I'm meant to be working in log10 or log2?)
1.00000^0.00000 = 1.00000

100^0.5 = 50 or in log10 2.00000^0.30103 = 0.60206

100 (1/0.2) = 5

see how I'm doing before I carry on

& to divide, you minus exponents, having time to play is wonderful now I've got over my base e OCD must solve

Well, theres nothing like a challenge is there

Well, my wall isn't going to stand for long if I don't put the foundation in, I know exponent rules, but it is good to practise & have some one say yes, you've understood or no, youve got that wrong

If I haven't finished the answers, it's because I might have to get off computer, not that I've given up

What I'm not understanding is why the answers are not matching the log table which means I should have got these wrong

Last edited: Apr 17, 2012
3. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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Your making up answers. The first three problems don't need to involve logs. Only exponent rules.

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5. ### Muttley600New Member

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That is where I'm getting confused, I'm not making up answers, I simply aren't relating to it if they are wrong
This is the first time I have actually tried to answer something like this from my own (wrong, by the looks of it) understanding
I understood that there was a logarithm for each & every number & by using two numbers together, they can give us the sine, cosine etc
Is this not true?

Ok, let's put you in my shoes so you can see my picture for a moment, then you can tell me where I went wrong, after reading all your links & remembering a link a fair while back, I have this picture that looks like a ball.
The centre of this ball = 0 (which in turn = 1, the anything & everything object) I'm seeing this as base e or log2
The outer radius of the ball = 2 radians (any way around its shape) or again 360degrees or log10

Anything outside of this is the magnitude of the ball (*by)

So I'm seeing logarithms as giving us any angle for a given number inside this ball

Now, is it possible to correct me with a picture?

This is the first thing I've learnt & probably why I'm intrigued by this subject as everything I've learnt to date in my life has been by ear,feel or respect, never by reading data

Either you a very kind soul to stick with me or did something really bad in your last life.lol

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6. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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OK, the 100^(1/2) is really √100 or 10. The whole point is (1/3) power is cube root, 1/2 power is square root, 1/6 power is the sixth root etc.

Exponent rules. The bases MUST be the same.

MULTIPLY: Add exponents. Yea I tricked you. (10^2)*(10^2) may have been easier. That answer is: 10^4. 2+2 = 4.
I gave you exponents of-1 and 3, so -1+3=2 and the answer is 10^2.

DIVISION is Subtract exponents. Yea, I tricked you again. (3-(-2)) = 5, so the answer is 10^5. It's 1000/0.01=10^5

You could have used your trusty calculator to get these same answers. Try raising 100 to the 1/2 power and see if it's not the same as the sqrt(100) or 10.

Got it?

Last edited: Apr 16, 2012
7. ### Muttley600New Member

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Ok, im going to have to reply to each one seperately as im onphone & its easier
so fractions cannot be converted to decimals
& two bases side by side are *

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8. ### Muttley600New Member

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Your going to kick me, surely you do inside () first, so I'm seeing that as 100*100= 1000
Where did the other 10 disappear too?

9. ### Muttley600New Member

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At least i got the exponent right (read:looking for the smallest glimmer of hope here.lol)

10. ### Muttley600New Member

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Ok, i clearly missed that one completely but it gets worse, not only did I miss exponent, I see 10^5 as first part of your answer but where did the /0.01 come from

Not very good at this am I........I hasten to add..........yet

11. ### Muttley600New Member

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How do you raise on calc?

That's it, I'm done now, well nearly, is it Halloween over there.lol

Last edited: Apr 16, 2012
12. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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Hey, what does 100 * 100 equal? It's not 1000. You'll find your extra zero.

---

10^3 is 1 with 3 zeros or 1000 or 1e3
10^(-2) is 1E-2 or 0.01, remember moving the decimal two digits to the left. Iused the 1000/0.01 as ANOTHER way to solve the problem.
The EASY way was to subtract the exponents. the HARD way was to do each calculation separately and do the divide.

Dividing by 10/0.1 moves the decimal place of 10 to the right 1, so you get 100. Guess what dividing by 0.01 does?

And yes 10^2 is equal to 10 * 10 and 1E2 because the "En" means multiply by 10^n or in pictures: Means move the decimal point.

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13. ### Muttley600New Member

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I forgot the decimal moves with zeros, so if I add a picture of a decimal point connected to AC, I now have an oscillation so it has the ability to move back & forth
You may have just solved my problem with the decimal point

So am I still alright to use my ball if I adapt it, if I change 1E to negative (inside the ball) & 1e to magnitude (outside the ball)
But that does leave my log theory in a mess as I was seeing 1e or base e as centre

Thanks for the correction

Last edited: Apr 17, 2012
14. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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You want a theory for LOGS? How about LOGS are like planets, base camps,countries, Languages (examples: 10, 2, e) Each place uses it's own language or BASE, but just like Bleistift is the word for Pencil in English, 10 decimal (English-a universal or common language) is like Pencil as 1010 is like Blesiteff is to German. The number 1 or zero might be words which are the same in ALL Languages.

You can convert from any base (language) to any other base.
are Languages. Bases are planets, countries or languages.

15. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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5+2 = 7 so it's 10

It's like having 2 tens (10)(10) multiplied by 5 tens (10)(10)(10)(10)(10).

So you have 7 tens

Negative exponents are a little tricky, BUT there is another IDENTiTY that states that staes that

or that dividing by (stuff) is the same as multiplying by it's INVERSE or 1/(stuff)

so

That's all that's happening.

---

Calculator:
You should have a button on your calculator labeled:

I only own an RPN (Reverse Polish Notation Calculator) so I am of little help.

So, I use something like 2 enter 3 enter

There are no parenthesis on my calculator. To evaluate: 5-(1+3)/10
I would use 5 enter; 1 enter 3 enter + 10 divide -
There is a 4 level Stack in the calculator and one element is the display.
An enter "PUSHES" an item on the stack.
An operator like "+" operates on the last two items on the stack and puts the result in the display.
----

Past life comments: Basically I enjoy a challenge.

Last edited: Apr 17, 2012
16. ### Muttley600New Member

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ok, throw some easy ones at me, whats the worse that can happen I get them wrong & look stupid, well, you all know I mastered that long ago, so the only way is forward

[Error: Image\ is\ too\ big\ (1427x91),\ the\ limit\ is\ 700x300]

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17. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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Fixed the gibberish. Mismatched Latex tags/ The last one is supposed to have a "/" in front of Latex. Look at post 234 again.

That answer is not 4. Hey, you have MS Word, right? If You have Excel you can use it. e.g. =4^(1/2) in a cell.

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18. ### Muttley600New Member

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Thanks for fixing, so does x^2 x^3 = x^5?

Ill take a photo of buttons on phone calc & show you how it's working tomorrow on that sum

Unfortunately I don't have enough money to indulge in
excel :-(

Last edited: Apr 17, 2012
19. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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Yes.

Filler: ***********************

20. ### cowboybobWell-Known MemberMost Helpful Member

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Just watchin' and learnin' from ya'll and playin' with tubes here.

I've got a feeling that TINA (maybe other sims as well) just treat tubes (rectifiers like the 5U4GB) as high voltage, relatively high current solid state diodes. Maybe not. Here's the pspice definition (note the stuff NOT modelled):

--------------------------------------------------------------
* 5U4GB pspice rectifier model
*
* The following parameters are not modelled:
*
* (1) Filament and filament warmup time
* (2) Reverse voltage breakdown
* (3) Saturation
* (4) Inter-electrode capacitance
*
* Please note that this model is provided "as is" and
* no warranty is provided in respect of its suitability
* for any application.
*
* 5U4GB maximum ratings:
*
* PIV 1550V
* Max in 550V RMS
* Ia pk 1000mA repetitive (4600mA transient)
*
*
* .----- Anode
* | .--- Cathode
* | |
.SUBCKT 5U4GB A K
GP A K VALUE={7.55E-4*(PWR(V(A,K),1.5)+PWRS(V(A,K),1.5))/2}
.ENDS 5U4GB
----------------------------------------------------------------------

I'm going to see what they do with a triode. And here it is:

----------------------------------------------------------------------
* 12AU7A Triode PSpice Model 8/96, Rev. 1.0 (fp)
*
* -------------------------------------------------------------------
* This model is provided "as is", with no warranty of any kind,
* either expressed or implied, about the suitability or fitness
* of this model for any particular purpose. Use of this model
* shall be entirely at the user's own risk.
*
* W. Marshall Leach, jr: "SPICE Models for Vacuum-Tube Amplifiers";
* J. Audio Eng. Soc., Vol 43, No 3, March 1995.
* -------------------------------------------------------------------
*
* This model is valid for the following tubes:
* 12AU7A/ECC82, 6680, 6C4/EC90, 12DW7/7247 (Unit #2);
* at the following conditions:
* Plate voltage : 0..400V
* Grid voltage : 0..-18V
* Cathode current: 0..30mA
*
*
* Connections: Plate
* | Grid
* | | Cathode
* | | |
.SUBCKT 12AU7A P G K
E1 2 0 VALUE={V(P,K)+18.28*V(G,K)}
R1 2 0 1.0K
Gp P K VALUE={10.88E-6*(PWR(V(2),1.5)+PWRS(V(2),1.5))/2}
Cgk G K 1.6P
Cgp G P 1.5P
Cpk P K 0.5P
.ENDS 12AU7A
---------------------------------------------------------------------------

This one does include inter-electrode capacitances, so I guess they really do model tubes.

I don't know how to edit or create a pspice model. Doesn't look all that complicated but, as I said, just don't know how. Definitely looking up the Leach book referenced above.

Last edited: Apr 17, 2012
21. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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Marshal Leach passed away a few years ago. My audio amp is basically designed by him. http://users.ece.gatech.edu/mleach/lowtim/faq.html The web didn't exist then and of course I made changes like 40,000 uF of capacitance and a custom 4 winding toroidal transformer. I had to design a slow turn-on ckt because of the large capacitance.

Anyway, I was outside for a couple of hours collecting a 30 gal trash bag of tree pollen.