# Understanding Electronics Basics #1

Discussion in 'General Electronics Chat' started by cowboybob, Feb 16, 2012.

1. ### cowboybobWell-Known MemberMost Helpful Member

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As many as you like.

(And), Three separate AC signals, 120 degrees out of phase with each other.

In a way, yes. Excellent.

Now for the AC to DC sim.

View attachment 61317

Where you're starting is with a rectified AC signal (Note the lack of the "negative going" portion of the AC signal). That's the result of the rectifier conducting in ONLY ONE direction).

Then we add in "filtering" (the cap).

Last sentence in sim text box with "500uF", Don't add the "F".

I'll be away from the machine for about 3 hours.

Last edited: Feb 21, 2012
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2. ### Muttley600New Member

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see you later CBB, I'll carry on having a play with sims

Cool, this is going to start me help understand what the actual components are actually doing, going to go have another look names of sims now in attachments, hover mouse over them

Last edited: Feb 21, 2012
3. ### cowboybobWell-Known MemberMost Helpful Member

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Outstanding!!

As you can see, as you add capacitance across the output of the rectifier circuit, the Trace becomes more "linear" or straight. The highs and lows are being smoothed out (the AC component of the signal is be filtered out).

This is because the capacitor is charging up on the positive swing of the rectifier output and then dis-charging into the circuit on the negative (or zero output cycle) of the rectifier, thereby sort of "filling in the blanks" between the highs.

Thus AC is converted to DC. What little AC "noise" that is left riding the top of the DC can be a problem in some circuits and not in others. For the time being, we're going to go with what you've learned thus far since it most closely mimics the original basic circuit we "reverse engineered".

Now we're going to look at converting a DC signal to an AC signal.

Give me a bit to make the sim.

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5. ### Muttley600New Member

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Cool, looking forward to it, all pancaked out now, the one time of year where I enjoy making tea

The bit I'm finding intriguing is the fact the cap is the other side of the load but there is no load reading, why is the resistor there?
then to top it, the cap goes to ground, meaning the power must be going in/out of same cap leg Edit: just read your post again, you've explained that bit with oscillation of AC signal, I don't mean to swear but that's bloody clever isn't it, I'm impressed, that is starting to mean something now

just thinking outl oud, give me time to figure this out, so see sim MUTT17, I took R1 out to see what would happen, now we have a perfectly DC biased signal, can't even see a ripple, however the V went up from about 1.4 to 1.85, so the cicuit was working as so, please correct me where I have misunderstood:
The rectifier was clipping the - side of the signal (below gnd) the resistor was altering the V, the cap was finishing with smoothing the signal out

Edit: so if you look at MUTT18 & change the sillyscope values, you get a ripple on auto trigger (ignore the vertical position, I was just playing, you can still see it on 0) but without resistor, cap seems to have minor effect at 1u but gets so you cant see the ripple as you increase the value of it.

I don't know if you realise but that was the best sim you've done so far, I've learn't loads off it

So how do you know how much load you could put on that if your just suppyling a given signal or is that for later?

Edit: I'm seem to be doing this a lot so the oscillation back & forth has nothing to do with the - & + side of the signal either side of gnd, I was confusing the two or have I got that wrong but if I have got it wrong then the cap can't work as you descibe & we have already got rid of the - side of the signal with the rectifier, that has to be right doesn't it, just remembered diagram I posted off other site about converting, it was still on about charging/discharging on cycles, so although they are tiny, cap still works on that basis, meaning the oscillation is the -&+ doesn't it

Got to get off computer in a bit but will still have phone on, also jobs to do in morning so will be back computer after lunchtime tomorrow, or about 08:00hrs your time, have a lie in

Last edited: Feb 21, 2012
6. ### cowboybobWell-Known MemberMost Helpful Member

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As you say above, the resistor added a load, thus reducing the voltage at the output. Very Good. I had R1 in there for no particular reason. It loaded the circuit some, that's really the only reason.

You might note, as well, that I increased the "Internal Resistance" of the Voltage Source. That, too, is affecting the circuit.

Good for you to try it without R1. Now your starting to think like an experimenter!

I also noted that you've got the "Coupling" set to "DC". Try the "AC" selection and you'll see that tiny bit of AC ripple.

What size load a power supply circuit can handle is dependent on several factors:
Current capacity of the:
1. power supply (battery, etc.)
2. the rectifier
3. the capacitor.

In other words. all of the components. Sizing for load is another chapter, if you will. For the sims we assume current is primarily limited by the rectifier's limit (per the specifications) OR the limit imposed by a fuse, were we to put one in the circuit (which we will, eventually).

I'm still working on the DC to AC sim. It's just an oscillator, but I want it to be a basic as possible to simplify the explanation of its guts.

Till the morrow...

Last edited: Feb 21, 2012
7. ### Muttley600New Member

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I haven't gone for the night, just needed to clear computer for Lou.lol

So we can alter the internal resistance on sim, what does that mean with components?

8. ### cowboybobWell-Known MemberMost Helpful Member

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For instance, with the AC sig gens, if I were to hook them up in parallel (as in the 2 AC Frequencies example sim) with an internal resistance of zero (0), it would return an error indicating an over-current situation (A short) between the two of them, and the simulation would fail.

By introducing an internal resistance, the current is limited and that clears the over-current error.

What it does, as well, is to throw another resistance into the mix of components (both series and parallel) that alters some factors within the overall circuit. Ordinarily not so much as to make a real difference, but in some cases it can be problematic.

I usually don't concern myself with the internal resistances of the power sources because I don't usually hook them up in series OR parallel.

9. ### Muttley600New Member

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Fair enough,I'm never likely to either, it's just nice to understand what we are doing & why which you explained.

What a great day
Thanks CBB
Night

10. ### Muttley600New Member

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I think I can just get away with saying morning CBB, late as always, becoming a bad habit.

11. ### Muttley600New Member

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Well, the way my curiosity is, I'm glad this isn't real power on sims, but I had to try it didn't I It still gave a waveform

Even trying both VG1 & 2 at 240V ampitude still gives a wave, how & where does the short occur?

Last edited: Feb 22, 2012
12. ### cowboybobWell-Known MemberMost Helpful Member

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Afternoon Graham,

Operative word here is Parallel, not series.

When the VG's are hooked together in parallel, they are, in effect, in series with each other, but in a closed loop. See below.

View attachment 61364

13. ### Muttley600New Member

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Afternoon CBB

Wow, that's weird, going to have to try that now

Am I ready for different understandings yet, there must be more to AC?

14. ### cowboybobWell-Known MemberMost Helpful Member

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Yes. Lots.

Sad to say, I'm still working on the oscillator. I'm finding it pretty difficult to come up with a simple, one transistor schematic. Not a problem with a 555 timer, but I want you to be able to see the whole concept, part by part.

I'll get it, though.

15. ### Muttley600New Member

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I don't mind if you add more parts, something else to learn but I do get what your saying

16. ### Muttley600New Member

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Been having a read of project again while your trying to sort sim out, looks like it needs breaking down into parts to fully understand what I'm dealing with, as always, looking makes me question things

What is this oscillator that you & KISS are on about & how does that work? Or is that what your working on at the moment

Anyways, goodnight & I'll try & break project into sections until you get up to give me something to do

17. ### cowboybobWell-Known MemberMost Helpful Member

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I had a little plumbing problem (I'm on well water) that needed tending to. Just now finishing up.

I'll be back at it here thinking nothin' but "tronics"tomorrow. I promise.

Last edited: Feb 22, 2012
18. ### cowboybobWell-Known MemberMost Helpful Member

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Good morning, Graham.

While I'm slaving away at the AC issue, what do you think of a re-cap of what we've covered thus far?

How about you letting me know what you feel pretty solid with up to now and what may still be "foggy" for you.

Let's start with (just basic definitions of (and/or purpose) of the components we've covered:

battery, resistor, capacitor.

then DC, what is it and how is it useful

Then AC, same question

then how the two can interact.

This is NOT a test!!. Just an exercise.

Chortle...

19. ### Muttley600New Member

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& boy do we all get stuff throiwn at us that needs sorting had passport rejected, spent hours sorting it out, all done now

Hope you got sorted yesterday CBB & I still caught you in the morning, glad your five hours behind me

20. ### Muttley600New Member

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Sounds perfect, I could do with something simple for five minutes after this morning, what can I say about a battery, it supplies DC power

A resistor can be used to create a load (current-'I') on a sim, they vary in size & shape & colour, the readings are in Ω on ameter, the value is dependant on the circuit, not so important on sim for teaching but when we get to do something as a real circuit, they will need to be worked out properly........I also have a mental block on the decimal point which is going to make me very wary of getting the right one, I'm sure as we progress you could be picking me up on this in the future, they can also be used on either AC or DC circuits, they can either have four or five bands around them which will tell you the value of them, the four band ones read as follows:
1st & 2nd band denotes digits, 3rd is a mulitplier with the 4th as a tolerence for value, the five band one has a third digit in the middle.......bet you didn't think I could sat much about a resistor did you

Edit again: they actually alter voltage as well

The cap value is read in (edit: just noticed after typing last bit that values can be changed) I have only seen values as low as 1uF up to 100uF so far, you could let me know how high they do go. They only work on Ac as it works on both signals - & + of ground, one side they charge up & the other they release power to smooth the voltage- this also means that any noise on the circuit is reduced.
There was also that other cap that looked flat sided but round but I'm presuming that works on the same principle just a different value, so these too can come in variuos shapes & colours

direct current, basically a stable (noise free) voltage supply with only a single wave, I would have even gone as far to say that it is just an AC signal manipulated but if it comes off a battery it is a stable supply, DC has a flat waveform until changed by AC

AC current is alternating current which oscillilates back & forth giving us a - & + waveform either side of ground (feel free to correct me up if these are two seperate things) Waveforms can be mixed in multiples to create waves within waves, altering the frequencies, it is measured on a sillyscope by the p-p ampitude of the voltage & time via frequencies, the pahes alters the cucle of the wave.

If you add DC to an AC wave, it can lift or lower the voltage

Talking of which I need an hour to grab some tea.

i take it inductors work on the same principle as caps but for current

What happened to KISS, haven't seen him on here for a few days

Five weeks to get that far, is that good or bad?

Last edited: Feb 23, 2012
21. ### cowboybobWell-Known MemberMost Helpful Member

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OK, Here we go...
Yes.

Yes. (My emphasis.) The resistor, by creating a load, limits the current. Very important, And by limiting the current, it generates a voltage across itself.

On the issue of capacitors:
1.
Essentially correct. These are the Polarized caps. They are marked as such by having a leg marked + or - .

2.
These are the Non-Polarized caps. Their orientation in the circuit is NOT dependent + or -. They are generally used to pass an AC signal with a circuit and block any DC present with that AC signal. They are also essential to an oscillating circuit, which is where we're heading.

Good start, Graham.

Yes.

Yes, except phase doesn't alter the cycle of the wave. The phase (a value between 0 and 360 degrees) is the starting point of the cycle of a single wave. Phase is usually found being discussed when two or more separate AC signals are involved. Like "3-phase" motors. There is more to learn about this yet, but it's not essential to where we are now.

VERY good with the inductor insight. You're starting to get the deeper correlations now. Although in one aspect they differ (from polarized caps) considerably: an inductor (at room temp) cannot hold a charge like an electrolytic cap. When power is removed from an inductor, the EMF collapses rapidly (but predictably), expending the energy it had momentarily stored. But then, that's what makes them useful in oscillating tank circuits.

Sort of miss KISS, ya know. Might have to PM him.

Yeah, it's been 5 weeks, but given where we started and where we are now, I think that's pretty impressive.

Last edited: Feb 23, 2012
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