Understanding Electronics Basics #1

[Muttley600]

Think I've covered that now apart from questions about cicuit, but I'll let you correct me first **broken link removed**

Period is not another term for wavelength. It Muttley's head it may look like it. Period has the units of time and wavelength has the units of length. Time and length are unfortunately the "same" on your sillyscope, but period and wavelength are NOT the same entity.

but they have the same 'e' numbers if I'm correct even though they are two different things

I'm doubting that now?

I was right to doubt :-( I have checked frequency & it is wrong

 

[cowboybob]

Period is not another term for wavelength. It Muttley's head it may look like it. Period has the units of time and wavelength has the units of length. Time and length are unfortunately the "same" on your sillyscope, but period and wavelength are NOT the same entity.

My Emphasis.

KISS is correct. He's also correct that a scope can lull one into confusing the two.

As we have been discussing the wavelength of a single cycle, it is very easy to mix both the "time" taken for the cycle to complete from start to finish (its frequency) and the "distance" traveled on the scope screen ( the number of graticules from start to finish) which is divided into time segments, from which we derive frequency. Go to the bottom of the post for a further explanation.

But, still and all, he's right.

So you taught me R*C then give me something totally different

No. I wanted you to see a "practical" application of the use of an RC circuit. In this case, to control the "width" (duration, or time on [or off], for that matter) of a single pulse that is controlled by the RC circuit (≈1 second). From that understanding we can investigate (and already have, actually) how an RC circuit can control the "frequency".

It's only in this circuit that the frequency of the signal is controlled by the "period" of the trigger switch (4 seconds), which is 1 divided by 4, or 1/4 Hz, or 0.25Hz.

I can see the trigger is every 4s & the pulse is every 1s

Let me rephrase your sentence: "...the trigger is every 4s (true, BUT) & the pulse is every 4s also. See below:

View attachment 62504 Please excuse the crude lettering.

but my ism looks like it has ripples where yours is smooth?

The resolution of the scope screen and a little trigger "jitter" ( an electronic excuse) is causing the less than perfect presentation. While I was looking at mine it jittered as well. When I took the snip shot it just happened to look gooder. Don't worry about it.

395.57ms wave length so I'm guessing 395.57KHz

No. And I'm going to have to eat a little crow here. Let's call it "wavelength in seconds" because, in point of fact, wavelength, as a term by itself, is a distance traveled, NOT a time. But for the time being, when you see the term "wavelength" think "wavelength in seconds", especially when we're using the scope.

The time between one trigger pulse and the next is 4s, as determined by the switch. See below:

View attachment 62505 I have GOT to get some kind of lettering app for the snip tool...

I know this is tough, if for no other reasons trying to nail downall the definitions of all the terms. You'll eventually absorb it, so long as this instructor can quit making mistakes...

 

[KeepItSimpleStupid]

I did ask you to read up until "standing waves" here: https://en.wikipedia.org/wiki/Wavelength

λ = v/f. We haven't covered this at all. v is the speed in which it travels in the medium. In a vacuum, the speed of light is aprox 3.8E8 m/s.
λ is the wavelength. f is the frequency and v is the velocity. This number dictates how big antenna's have to be for radio frequencies. The antenna can be any evenly divisible multiple of the wavelength long. It's not uncommon to design antenna's for 1/2 or 1/4 wavelength. Telephone antenna's are really small and a TV antenna is much larger.


The other term you need to be familiar with is f = 1/period.

 

[KeepItSimpleStupid]

is a distance traveled[/U], NOT a time. But for the time being, when you see the term "wavelength" think "wavelength in seconds", especially when we're using the scope.

Teach Muttley the correct term: A wave whose period is: 395.57ms; If you want frequency do the math 1/395.57 ms.

Making sure any answer has the correct unit has to be drilled into his head. That concept was drilled into mine a little late.

Units are extremely important.

PS: CBB: You haven't taught him to use the cursors, or have you?

 

[cowboybob]

Units are extremely important.

And I know that, but I painted myself into a corner and didn't know when to stop. Thanks fro keeping an eye out for me.

I need to amend a graphic in post# 462.

Where I labeled the scope display "frequency", that was the wrong term.

It should have looked and read like below:

View attachment 62511

Sorry for the error.

PS: CBB: You haven't taught him to use the cursors, or have you?

No. I haven't. The scope face where the cursor info is displayed is extremely "busy" when data is displayed and can be quite confusing for a new user. And we haven't gotten it clear, exactly yet, as to what represents a complete cycle, so...

But, perhaps, now is the time.

Thanks for the input.

CBB

 

[KeepItSimpleStupid]

www.irfanview.com is a great free graphics program for conversion and viewing especially with all of the so called plug-ins. Under edit, use "show paint dialog". The program can open so many kinds of files which means the directory file filter fails at times. Certain files are part of a class like pdf. You can only do one "undo" function and it's not a graphics program with so called "layers".

 

[Muttley600]

Quick scan through, looks like I have lots to learn

I'm accurately measuring by exporting graph & altering lower table to minute detail

I don't know what I'm doing wrong, I'm getting 2.52799Hz not 25Hz, it's going to be that blinking decimal point again isn't it :-(

Well, thats me for the night, back tomorrow

What about my RC calculation?
Why did I have to put 50ms where you put 5?

Night both

 

[cowboybob]

Last things first.

What about my RC calculation?
Why did I have to put 50ms where you put 5?

With the timed switch settings "t On" set to 1ms and "t Off" set to 5ms, the trigger trace on the scope just looked like a very brief down-going "spike". It's interesting you chose to extend the "t Off to 50ms ( as I did in subsequent tests) because that gave the scope trace of the trigger pulse a better "definition" in the trace (easier to see).

I don't know what I'm doing wrong, I'm getting 2.52799Hz not 25Hz, it's going to be that blinking decimal point again isn't it :-(

For one thing, the answer is 1/4 Hz, which is 0.25 Hz, not 25 Hz. Your off by a factor (multiplier or divider) of 100. So yes, the decimal issue is beating you up. Don't know what to tell you other than to just keep practicing.

As KISS suggested, I'm going to demonstrate how to use the "Cursor" functions on the scope. These allow for more precise determination of timing (X axis) values.

The sim "snips" will be posted shortly. (I have GOT to re-boot this machine - slow as molasses in January).

 

[Muttley600]

On phone for now so spending time looking at differences

λ means wavelength & is measured in 'm'etres & 1000mm = 1M

λ is inversely proportional to Frequency (what's the symbol for 'f'?)
Meaning the exponent numbers go in opposite directions to each other

So 1Hz = 10 (ex 0)
1s= 10 (ex 0)

1KHz= 10 (3)
1ms = 10 (-3)

So wavelength is measured over distance
Frequency measured over time
No point going into velocity yet as we haven't covered phase

So again, to get frequency I measure like so:
1/ (time) = frequency



Morning (in your time) CBB

 

[Muttley600]

Yes, I'm still getting beaten up by decimal point, as you say (hopefully) practise makes perfect

Got it **broken link removed** they say simple things please simple minds **broken link removed**

I was seeing it as 395ms where really it was 3.95s

 

[Muttley600]

No. I wanted you to see a "practical" application of the use of an RC circuit. In this case, to control the "width" (duration, or time on [or off], for that matter) of a single pulse that is controlled by the RC circuit (≈1 second). From that understanding we can investigate (and already have, actually) how an RC circuit can control the "frequency".

It's only in this circuit that the frequency of the signal is controlled by the "period" of the trigger switch (4 seconds), which is 1 divided by 4, or 1/4 Hz, or 0.25Hz.

Cool, now I now what I'm looking at I can have a play

Let me rephrase your sentence: "...the trigger is every 4s (true, BUT) & the pulse is every 4s also. See below:

View attachment 62504 Please excuse the crude lettering.

Hopefully link below will help you & yes I see my mistake on timing

I know this is tough, if for no other reasons trying to nail downall the definitions of all the terms. You'll eventually absorb it, so long as this instructor can quit making mistakes...

No need to beat yourself up, you don't know what your working with this end & thats with me wanting to learn **broken link removed****broken link removed**

I know I'll get it in the end, it just may take a while **broken link removed**

 

[Muttley600]

**broken link removed**

I've just been playing with 'paint' in windows 7, you can add text via that as well, so save snip, open it in picture libary, then right click & choose 'edit' (4th line down)
then you'll find a little 'A' on the left hand side of brushes & hey, voila, ability to add text

 

[cowboybob]

yes, i'm still getting beaten up by decimal point, as you say (hopefully) practise makes perfect

got it **broken link removed** they say simple things please simple minds **broken link removed**

i was seeing it as 395ms where really it was 3.95s

YES! You've got it!!

 

[KeepItSimpleStupid]

So wavelength is measured over distance
Frequency measured over time

Don't use the word over because it can mean divide as in 1 over 4 being 1/4.

So wavelength is measured in distance units
Frequency is measured in cycles/s or Hz (or some of the other variants such as MHz or KHz)

Velocity is just another word for speed, but km/h isn't appropriate. Science uses the kgs (killograms,meters, seconds) system or the cgs (centemeters, grams, seconds) system.

 

[Muttley600]

Don't use the word over because it can mean divide as in 1 over 4 being 1/4.

So wavelength is measured in distance units
Frequency is measured in cycles/s or Hz (or some of the other variants such as MHz or KHz)

Velocity is just another word for speed, but km/h isn't appropriate. Science uses the kgs (killograms,meters, seconds) system or the cgs (centemeters, grams, seconds) system.

So I have been relating frequency to ms but really I'd accounted for cycles = t, as in 2∏ = 1Hz but I was seeing 1Hz as 1s


man, I'm confusing myself now **broken link removed**

ok, lets start again:

we have three main units we are talking about here: or is that four **broken link removed**

We have - distance/length = λ = wavelength
cycles/Hz = frequency (is this the ∏)
phase/speed/velocity = time

& all this is on the spring opening & closing nothing to do with amplitude because thats relating to VP or ωV


If that's right, you mean we can tell three different things from this but they all look the same, I'm TRYING not to see them as the same thing........honest I am **broken link removed**

 

[cowboybob]

λ means wavelength & is measured in 'm'etres & 1000mm = 1M

λ is inversely proportional to Frequency (what's the symbol for 'f'?)
Meaning the exponent numbers go in opposite directions to each other

So 1Hz = 10 (ex 0)
1s= 10 (ex 0)

1KHz= 10 (3)
1ms = 10 (-3)

So wavelength is measured over distance
Frequency measured over time
No point going into velocity yet as we haven't covered phase

So again, to get frequency I measure like so:
1/ (time) = frequency

Very good. Suddenly, you've got it. Very, very good.

I've been working on the Scope "cursor" demo. This feature is very useful, but not at all easy to explain how to use since there is SO much info displayed and not a little confusing when it it is.

It does afford a level of precision (for both timing AND amplitude values) beyond what you can get just "eye-balling" the scope face.

But, truth be told, for all the years I've used scopes (over 53 now, since I was 11), it's only recently (two years ago) that I've had a real (not a virtual sim) scope that has cursors (last CRT type [no cursors] was a Textronix 922A, which was a fantastic machine, but the HV went and for the price of replacement parts I got a hand-held digital type that is a-maz-ing).

Anyway, again, I have generally used a scope for the "gross", (that is, generally accurate enough) circuit analyses that I perform.

For instance, "Is there even a signal being generated by whatever I just designed???" "Forget frequency and amplitude!! Is the damn thing even oscillating??!!??"

For the more accurate real world readings (if I want or need them) I use other instrumentation (digital freq meters, VOMs, and now the digital scope, which, BTW, gives me everything in side bars: Freq, Amplitude, Phase, PP, dB and more,).

Just my methods. I will (eventually) get around to the scope cursor demo.

 

[Muttley600]

I did ask you to read up until "standing waves" here: https://en.wikipedia.org/wiki/Wavelength

I did & have done again, I'll keep reading it until I understand it **broken link removed**

λ = v/f. We haven't covered this at all. v is the speed in which it travels in the medium. In a vacuum, the speed of light is aprox 3.8E8 m/s.
λ is the wavelength. f is the frequency and v is the velocity. This number dictates how big antenna's have to be for radio frequencies. The antenna can be any evenly divisible multiple of the wavelength long. It's not uncommon to design antenna's for 1/2 or 1/4 wavelength. Telephone antenna's are really small and a TV antenna is much larger.

These are my lightbulb moments that keep my desire to learn alive no matter how much I struggle, I will get & TOTALLY understand this, you know we did a comms test run the other day on bikes with external ariel, this has gain numbers etc (at bottom of page)
I want to be able to understand what this is tellingme, how it is (or isn't) an improvment over the smaller ariel we use, so I shall keep plugging away, I will never give up **broken link removed**

The other term you need to be familiar with is f = 1/period.

So I can relate F = a time period (be it, hours, minutes, seconds or ms)

even though you've just told me F is in cycles **broken link removed**

EDIT: got it, it means f=1 (cycle/Hz) / time

Don't panic, I will get it in the end **broken link removed**

 

[Muttley600]

Just my methods. I will (eventually) get around to the scope cursor demo.

You mean like this

View attachment 62553 View attachment 62554

MUTT77 scope sim taken from
MUTT78 showing cursors measuring XA - XB = DX

X = width, soory Time/period
Y = hieght, sorry (whatever it was showing us)

 

[Muttley600]

Very good. Suddenly, you've got it. Very, very good.

ok, it gets even more confusing now

Frequency is equal to velocity according to link

& was determined in cycles before Hz, no wonder there are so many variations

but intriguingly exponents are shown as + to frequency & - for λ but surely they are the other way around **broken link removed**

Thats it, I've caught up

I can see F, wavelength as different things

so in my ariel attachment 1/2 wave simply means half a radian or half wave

Does that mean below or above gnd?

ok, what does 'cos' & 'sin' mean?

How cool is this **broken link removed**

 

[KeepItSimpleStupid]

I won't be able to say much. On phone. But RADIAN FREQUENCY = 2*PI*f and is denoted by the greek lower case omega.