Understanding Electronics Basics #1

See below.

View attachment 62085

BTW, I'm pulling the signal off at the emitter (as opposed to the collector) so the load doesn't interfere (or doesn't interfere as badly) with the oscillations.

Which is also why some manner of amplification will be necessary to achieve the current level desired.

Good spot CBB, missed that little wire there be on puter in a bit

Ok, had a play, do you know by altering input V waveform changes, does this affect the frequency?

How are you checking F if not with multimeter?

Burning urge to understand & don't seem to be getting much time lately, so up at 7am, all chores done & raring to go **broken link removed**

More capicitor questions **broken link removed**

I can see we alter the frequency by altering the phase of the cap, which is easy on the sim, how is it acheived in real world terms **broken link removed** after looking at some datasheets to try & help myself get a better understanding I'm no further forward.
Take what this is showing for example:
View attachment 62107

I can see that it is a 100uF cap, it seems to be affected by the tempreture, the colder it is the more energy it uses (is that right) & it gives us 175 mArms - what are they

Now looking at the datasheet here & knowing frequency is adjusted by charge time (you know what I mean) the only reference seems to be in the dimension section & it seems to be showing the length of the - lead as altering the time, is that right or have I lost the plot, if it is right, how do you know what length to cut it to **broken link removed** it seems it would need to be very precise if that is right **broken link removed**

Then that would lead me to ask, how do you stablise V so you get the effect you want as my motorbike for instance varys V depending on the revs

Morning to you both when you get up **broken link removed**

& what do Wv & Tan stand for

Morning, Graham.

Let me get a cuppa [EDIT]: (and a smoke) and I'll be with ya.

I'll edit this post.

I can see we alter the frequency by altering the phase of the cap

Click to expand...

Not the phase. The capacitive value. A capacitor will alter the phase. Maybe what you meant to say was "by altering the phase with the cap"?

it seems to be showing the length of the - lead as altering the time, is that right or have I lost the plot

Click to expand...

In the datasheet, the - lead length is only an indicator that that particular lead is the negative side of the cap. Nothing more.

Generally speaking, when securing a capacitor to a PCB, you put the body of the cap as close to the board as possible. As a result, lead length is meaningless.

how do you stablise V so you get the effect you want

Click to expand...

Well, that brings us back to the voltage regulation issue. The last thing we might add to the DAD (DC - AC - DC) would be, for instance, a LM7805 or equivalent (5VDC reg).

Let's get our DAD running right with a reasonable current capability and then we'll address regulation.

Thanks CBB, think I'll join yer **broken link removed**

cowboybob said:

Not the phase. The capacitive value. A capacitor will alter the phase.

Click to expand...

hmmm, that's strange, if values alter the phase, why do you have to alter phase on seperate thing to value on sim **broken link removed**
Are you now going to tell me theres a lot of 100u caps with different phases or I'm still not understanding the full workings of them am I

Edit: I'm offically a numpty, it is the sinewave on the Voltage generator we alter phase on in the sim isn't it, not the cap, ignore my ramblings**broken link removed**

cowboybob said:

In the datasheet, the - lead length is only an indicator that that particular lead is the negative side of the cap. Nothing more.

Click to expand...

oh ok, why has it got something about 15min & 5 min **broken link removed**

cowboybob said:

Generally speaking, when securing a capacitor to a PCB, you put the body of the cap as close to the board as possible. As a result, lead length is meaningless.

Click to expand...

Fair enough

cowboybob said:

Well, that brings us back to the voltage regulation issue. The last thing we might add to the DAD (DC - AC - DC) would be, for instance, a LM7805 or equivalent (5VDC reg).

Click to expand...

ok, thats for later, I can live with that, one step at a time **broken link removed**

cowboybob said:

Let's get our DAD running right with a reasonable current capability and then we'll address regulation.

Click to expand...

Good plan, I need to understand how to change this around properly before moving on

Edit: so how are you measuring the frequency then CBB **broken link removed**

ahhhhhhh, that went too quick, have to be in work for 12 for meeting today

Once I understand how we are measuring frequency I will be able to see how the changes affect circuit then, making it more playable if that makes sense

I have been trying to get the signal analyzer to work but it keeps asking for input even though I've put VF1 as imput?????

In the dimension section of the capacitor datasheet, there is a thingy that looks like a phase symbol and a big D and a little d. If that's what your talking about, then.....

Big D is the diameter of the capacitor.
Little d is the diameter of the leads.

Muttley600 said:

Edit: so how are you measuring the frequency then CBB

Click to expand...

Here's an example that should help demonstrate the "scope" method of frequency determination:

View attachment 62131

OK. We're going to investigate frequency issues for a bit. As to your question, I isolate one, single wave of the sine wave, count the graticules on the scope (10 in this case), multiply the sweep speed (100usec) time by the graticule count (10) to derive a "wave length" of 1 millisecond.

Then divide 1 (one) by that number (1 millisecond, as a decimal [0.001]), and get the answer of 1000 Hz, or 1kHz. For any wave length other than one landing exactly on graticule lines on the scope face is, at best, an approximation.

Generally, I consider this "close enough" for the circuits we 're creating and their use.

I have been trying to get the signal analyzer to work but it keeps asking for input even though I've put VF1 as imput?????

Click to expand...

To answer this question we will, for the moment, first investigate the "Function Generator" (FG) and how to use it.

First, the "Voltage Generator" (VG) View attachment 62115 that we've used before can also be controlled by the FG View attachment 62116. Whatever signal we tell the FG to produce will become the output of the VG into a circuit.

The beauty of an FG is that we can tell it to produce not just one frequency, but cause it to "sweep" across a range of frequencies over a period of time. That is, generate a signal, of a constant amplitude, that, say, starts at 100Hz and increases to, say 10kHz, and then goes back to 100Hz, etc..

This allows us to observe what happens to that signal when it is applied to, for instance, a resonant tank circuit made up of a capacitor and an inductor (not unlike the circuit in our 1 transistor oscillator).

Here's how to do it in the sim:

For starters, the Basic circuit:

View attachment 62118

There's no need to adjust the VG's parameters. We'll do that from the FG's controls. First we set the FG's sweep range (100Hz to 10kHz):

Start values: View attachment 62119 Stop values: View attachment 62123

Now we'll further adjust the FG: (set "Time" to 5s and "Num" to 20). press the "Sweep" button. Leave the "Cont" button as is. Then press the Control "Start".

View attachment 62122

Now bring up your scope and observe how the sweeped sine wave appears.

View attachment 62125

Pretty cool. huh?!?

In a bit, I'll post circuits and a lay out on how to use the Signal Analyzer (SG). We will not need the FG for this since the SG has a built-it FG.

So will all this lead us to be able to see frequency off function generator set up to copy battery output, I take it that is what it is doing?

This is a big hurdle to cross isn't it, once we can see frequency, we are well on the way

KeepItSimpleStupid said:

In the dimension section of the capacitor datasheet, there is a thingy that looks like a phase symbol and a big D and a little d. If that's what your talking about, then.....

Big D is the diameter of the capacitor.
Little d is the diameter of the leads.

Click to expand...

No, I thought it was on about altering time by length of lead as it shows 15/5mins but it seems not

WV (V) means Working Voltage in Volts and the snippet is saying 6.3 Working Volts

It's A 5 mm diameter x 11.5 mm high capacitor

The (Cap)acitance is 100 uf

The MAX Ripple it can stomach without blowing up is 175 mA RMS (milliamps root mean squared)

Impedance / 100 Khz really means Impedance at 100 Khz. The snippet shows the value at two temperatures.

A topic that hasn't been covered at all and needs some time devoted to it. Z is impedance. The units of Z is in ohms. It is frequency dependent.

https://en.wikipedia.org/wiki/Capacitive_reactance

This particular capacitor is suitable for use in switching power supplies.

CBB: It might be instructive to set up a resistive divider and a capacitive divider at some point or at least illustrate the -3 db frequency.

Graham,

Go back to post# 309. I've edited quite a bit.

KISS, good idea and will do.

Graham, good article to read but, for the moment, disregard the math in the wikipedia article and keep the following in mind:

For capacitors, the basic concept to realize is:

For capacitors:

"Driven by an AC supply, a capacitor will only accumulate a limited amount of charge before the potential difference changes polarity and the charge dissipates. (Thus) The higher the frequency, the less charge will accumulate and the smaller the opposition to the current. ( "Thus" and the Underlined and/or bold portions are my emphases).

For inductors:

"An alternating current has a time-averaged rate-of-change that is proportional to frequency, this causes the increase in inductive reactance with [an increase in] frequency [Or, the greater the opposition to the current in the inductor (My addition)]." (Underlined and text in the [ ]'ed portion are my emphasis and my addition).

Notice the difference between the two (as to current levels) with an increase in frequency. These opposite reactions are important to remember.

These reactions of capacitors and inductors to frequency change are the underlying features that allow them to be used, among other things, to allow for the creation of tuned oscillating circuits (tanks). Although not the only method.

When I get them ready, You'll be able to see (with the Signal Analyzer sims) how this all works.

This is all sounding great, will have a proper read when home tonight
Thanks both

Nah. Just think of it as more investigation into the properties of capacitors eventually.

OK. Here are some very simple series capacitor, with a 1meg resistive load, graphs and their charging curves as plotted on the Signal Analyzer (SG).

Note the various SG settings.

Play with all you like. Also, in particular, note that we are using a logarithmic scale for the frequency. This is because it gives us a much better graph of the capacitor's charging curve. You're welcome to change that as well.

These pics are, in order: a 1pf cap followed by increasing cap values by orders of 10, (10pF, 100pf, 1000pf [1nf]). Frequency sweeps go from 10Hz to 10MHz.

View attachment 62138View attachment 62139View attachment 62140View attachment 62141

Note how increasing capacitive value reduces the 3db frequency curve point. When we get to resonant circuits (tanks) this should help you to understand how and why they work the way they do.

Obviously you can play with the cap value as well. Going higher or lower than what I've shown will require that you modify other aspects of the operation of the SG.

I leave that to you to have fun with...

KISS. I'm leaving the math for this to you (as I am not so good with that element). The 3db rule should be a little easier to explain with the graphs as examples. Any changes to the graphs (horz. or vert. divisions, type, text w/ pointers, etc.) I can accommodate for you. Just let me know.

ok, just before going back to post #309 this was what I was on about on the datasheet, obviously, as per normal I've totally let it go **broken link removed**

View attachment 62142

Now lets go play **broken link removed** from all the info here there might be more questions

Just had a go with FG, so what your showing me there has actually taught me to use FG & waveform does not stay constant on a sweep, would that be similar to tuning a radio (if it was the right wavelength of course)

So the frequency changes when the waveform changes, hence things not interfering with each other

I've come off the computer for a bit but had a few questions that I'll ask in a bit but this isn't just pretty cool as per your last comment but really exciting, I'm loving this........*huge grin*
Looking forward to getting back on computer

The wave form you observe on the scope is a representation of the electrical potential variations of an alternating current (AC) as time goes by.

One complete set of those variations (from a zero, to max +, to zero, to max -, and back to zero) is one cycle.

The frequency is the number of cycles per second (as it used to be called). That same value is now referred to as Hertz (Hz) for the guy who actually first recognized the phenomenon. One Hertz is equal to one cycle per second. This is how it is ALWAYS described.

The FG is generating an AC signal, starting at 10 Hz (10 cycles per second) and then "sweeping" up to a higher frequency.