Understanding Electronics Basics #1

[KeepItSimpleStupid]

This should keep Graham busy for a couple of days: **broken link removed**

 

[Muttley600]

This should keep Graham busy for a couple of days: **broken link removed**

Busy day at work, plenty to read I see, KISS, if you wanted me to be quiet for a few days you could of just asked,lol

 

[cowboybob]

Not exactly what I was expecting.

Division on zero always results in infinity.

Since v is equal to L times the quantity di/dt, and since t=0 in this case, I is divided by zero, thus giving us an infinite v (How does one graph infinity?). This is true irrespective of the value of L or i.

The sim does the best that it can giving us a voltage value and not crashing due to the division by zero "problem". It actually takes a stab at it depending on the time allotted for the analysis. As we increase the time allotted to the transient analysis, the graphed peak v goes down.

Transient analysis:

View attachment 61581

Using the o'scope tool:

View attachment 61585 View attachment 61586

Same algorithms being used, I guess.

 

[KeepItSimpleStupid]

How about an inductor in Henrys. It looks like your in mH?

 

[cowboybob]

For your perusal:

View attachment 61587 View attachment 61588

First is with 1H for 1 fetasecond. Second is with 10H at 1 fetasecond.

Increased inductance by a factor of ten and that increased the V by a factor of ten.

It would seem that if we could decrease the time of the transient to zero seconds, it would attempt to display an infinite voltage.

 

[Muttley600]

I'm on post #85 now, am I catching up yet
Just popping shopping

 

[Muttley600]

At last, I got time to play **broken link removed**

Morning CBB

Ok, questions off attached circuit:

Why is there two batterys & not just one with 10V

Why is the one wave diffrent from the other, shapewise

Observations of circuit:

So the OpAmps are working as follows:
Point lead = output
Side leads = power in
Back leads power (looks like out but getting confused as to why we would have power out at point basically bypassing all the components, one = gnd, other = altering phase of wave via components

I take it this circuit has one output not two even though it looks like it (made worse by having two battieres) just two waves altering DC to AC, not sure on this because you could have one wave with AC couldn't you

I can't see why C1 is there as it is being bypassed as well?

I'll post & edit with more Q's

I can't even get my head around why there is a gnd lead between batterys, that would mean a dead short wouldn't it on VS2?

If they are the same opamps, why have the point leads got different 'v' out on meter?

This is raising lots of questions, ok, we haven't covered opamps yet, but my basic understanding should be getting there now shouldn't it

Need to get ready for work, back to phone for rest of day, man that went quick, I got up early today to get sim before work as well

 

[cowboybob]

OUTSTANDING JOB!!

I'm impressed with your having constructed the circuit with apparently no significant problems.

Very, very good.

At last, I got time to play **broken link removed**

Why is there two batterys & not just one with 10V

Some OpAmps work off of a single DC voltage source: some from dual. This is a dual source OpAmp. The reason for this involves generating a signal that can range between a positive and negative potential without hitting the "rail", which with a single source supply would be ground, which would result in a portion the negative swing (anything below Gnd, or zero volts) of the sine wave being "clipped", or cut off.

Why is the one wave diffrent from the other, shapewise

The Cosine output (VF2) is being "clipped" at its peaks. A vagary of this circuit. Don't worry about it for the moment.The Sine output is our focus.

Observations of circuit:

So the OpAmps are working as follows:
1. Point lead = output
2. Side leads = power in
3. Back leads power (looks like out but getting confused as to why we would have power out at point basically bypassing all the components, one = gnd, other = altering phase of wave via components

1. Yes.
2. Yes. (and out)
3. These are the inputs. For an OpAmp the two inputs are marked + and - to designated "non-inverted" (+) and "inverted" (-) inputs. In other words, a + signal injected into the + input will result in a + signal at the output. And if + signal into the - input, a - signal at the output.

I take it this circuit has one output not two even though it looks like it (made worse by having two battieres) just two waves altering DC to AC, not sure on this because you could have one wave with AC couldn't you

No. There are two, distinct outputs (at VF1 and VF2). In this circuit, to maintain oscillations, the output of OP2 is an out-of-phase (by 90°, the cosine) "feedback" signal to the input of OP1, which is then fed to OP2 (etc) to maintain oscillations. This circuit configuration is necessary in an oscillator that has no inductor to provide the "out-off-phase" feedback needed to maintain oscillations that are sine waves (as opposed to a square or sawtooth wave). Another concept that will have to be better explained later.

I can't see why C1 is there as it is being bypassed as well?

C1, R1 and R2 are part of the RC circuit that is causing the circuit to oscillate.

I can't even get my head around why there is a grd lead between batterys, that would mean a dead short wouldn't it on VS1?

Notice the + and - symbol placement of the batteries. VS1 is supplying the - potential to the OpAmps and VS2 the -. Their common other nodes are then grounded. Look carefully at the wiring: the only things across the outputs of the batteries are the OpAmp power connections.

 

[cowboybob]

Here's a somewhat simpler OpAmp sine wave gen to play with.

Same concepts. Note how long it takes the circuit to begin to oscillate (>250ms). Note also the phase difference between the two signals. Which, again, is what is maintaining the oscillations.

View attachment 61618 View attachment 61619 View attachment 61620 View attachment 61623

First image "Startup". Second "Running". Third "Snapshot Setup". Last "Snapshot Final".

Note also that VF1 is "clipped". VF2 is the signal we want and would use. I don't really care what VF1 looks like.

But, just to be clear, the clipping of VF1 is due to circuit anomalies, not the battery power arrangement.

 

[Muttley600]

No problems putting sim together, my understanding feels much better on this front

I've been staring at your answer to q3 for ages, flipping back & forth between sim your post, this is a nightmareon phone, should get on computer a bit later but are you saying you can put + into an Input on opamp & get a - signal out.....?

Your 2nd sim looks easier to understand, I feel a little sim project, my first experiment coming on

To say dual battery is to supply gnd side of signal, so I'll try one battery, one opamp etc to see what I get, I'll let you know what I get wave wise, prob nothing like.lol but it's good to play.
Edit: ok, experiment didn't give me any kind of wave, just a quick flash then very slight ripple, never mind, I haven't got full understanding yet so I'm not gonna beat myself up

So the cap is altering the timing with the opamp boosting the signal, the resistors giving required v, the z diodes did what in first sim? I thought they were to get required.....oh they are holding 5v aren't they

Now I am confused, the OpAmp is meant to be a signal booster as I understood it, if we have 5v going in, putting meter on shows 75.76mV at VF2**broken link removed** in DC but we are getting an AC signal, no volts showing in AC on meter...........I'm not even close to understanding this yet am I **broken link removed**

I thought my basic understanding of components was coming on

 

[cowboybob]

I've been staring at your answer to q3 for ages,... but are you saying you can put + into an Input on opamp & get a - signal out.....?

Yes. It's the internal design of the OpAmp to allow this. Just take it on faith at this time. I'll generate a sim that will show how to invert a signal's value from plus to minus.

On that note, however:

It is best to think of Ground, in a circuit such as this, as the absence of an electrical potential or simply the return path or as a "floating" ground. In this circuit, one battery has its negative terminal attached to circuit ground. The other has its positive terminal attached to the ground circuit. Between the other terminals is 10VDC (+5VDC to zero to - 5VDC). Now think of the ground as a signal ground, above and below which the signal can vary from the high as + 5VDC to the low as - 5VDC, around the central potential of zero (ground).

So the cap (see 1. below) is altering the timing with the (see 2. below) opamp boosting the signal (see 3. below), the resistors giving required v

1. (AND THE RESISTOR)
2. (2nd)
3. (AND CREATING THE COSINE)

the z diodes did what in first sim? I thought they were to get required.....oh they are holding 5v aren't they

You know, I don't know what the zeners are in there for: some sort of 1.4VDC bias? The most recent sim schematic doesn't have any.

 

[Muttley600]

Back on phone again, where do the evenings go? I'm off work again next week, have been having every other week off to get my holiday in before April 1st (start of new financial year for us) so great having time off but absolutely shattering as having to work twice as hard to get normal workload done, running on reserve at the moment :-(
I didn't take holiday earlier in year due to workload but march is really too busy for holidays, maybe we just have too much work these days.

Im taking a lot of things on faith, I have to at the moment

I see where your going with battery layout but this wouldnt be possible in a live scenario would it, this is just for sim purposes?

You'll be pleased to know I was able to skip the kindergarten bit of algebra learning.lol suppose I should be embarrassed but I gotta start somewhere :-/

Back tomorrow

 

[KeepItSimpleStupid]

An OP Amp is known as an OPerational Amplifier. It turns out you can add, subtract, invert, multiply etc.

An Ideal OP amp has an inverting input (-) which I'll call B, a non-inverting input which I'll call A and an output. All an OP-amp does is this: (A-B)* (A huge number) which is called the open-loop gain.

Practically, though, there is a lot more going on.

 

[Muttley600]

Practically, though, there is a lot more going on.

& that's where I need to start helping myself, so I'll dedicate mornings to learning algebra as you two are five hours behind me, then after 12 & evenings to learning electronic understanding of how components work, hopefully it shouldn't take too long, I can see letters are relating to math, just need to be able to put the two together to see what we're working out **broken link removed**

On lesson 7 here & all your odd names are starting to fall into place
**broken link removed** man, that's a relief **broken link removed**

 

[cowboybob]

I see where your going with battery layout but this wouldnt be possible in a live scenario would it, this is just for sim purposes?

No, it's used in the real world as well.

Construct the sim below as an explanation. Keep in mind that it's really just split batteries.

View attachment 61649

Change your "Input" "Hi" and observe the voltages. You'll note that VF1 (Ground) is zero volts. It is the reference point for the other two potentials, just as it would be in the OpAmp sim (where the OpAmp is the load). It is also considered a "floating" ground in that is is between the other two potentials.

In real life (and the sim), OpAmp inputs AND outputs are ALL referenced to ground. The power to the OpAmp is "isolated" by the component construction of the OpAmp.

And don't forget, the sim (as in the real world) would register an anomaly (like a short) as an error, if there was one.

 

[Muttley600]

OK, so now your telling me batterys can be used backwards to create a - potiential, I never knew that & I thought you'd already amazed me by connecting a + & - together on very first led question

so as long as only one side is gnd it is ok **broken link removed**

 

[Muttley600]

Re: MUTT35

You know, I don't know what the zeners are in there for: some sort of 1.4VDC bias? The most recent sim schematic doesn't have any.

So Z readings are as follows:
Top of Z1 = 75.6mV
Middle of both = 26.16mV
Bottom of Z2 = 0V

So basically they are bleeding power (dissipating heat) before gnd, we did the same thing with resistor, why use a Z for that **broken link removed**

That was just getting interesting using probe on sim while it was running was highlighting what each line was doing, just found as I had to come off computer, will investigate more tomorrow

 

[KeepItSimpleStupid]

I believe the zeners are there for amplitude stabilization using clipping or getting the oscillator to start. Way to difficult to even attempt to analyze at this point. See: https://en.wikipedia.org/wiki/Wien_bridge_oscillator The purpose of the Zeners is described here https://www.edaboard.com/thread30023.html in post #3.

Ground: This subject alone gets really messy. Just think of ground at this point as a reference. Birds sitting on a power line don't get electrocuted. Their reference is the power line. There can be multiple references. In real life there may be terms such as analog ground or digital ground.

Earth: The ultimate reference, however there can be a voltage across the earth too in the presence of a thunderstorm. Sensitive electronics 200 feet apart have been destroyed. I know of a data center that had to run fiber inside because of an electrical failure during a storm.

Protective ground: Usually the metal case. It only carries current during a fault condition. It may be used to shield the box.

There was an early term called "chassis ground" where signals were referenced too. Then the chassis became non-isolated and all the knobs became plastic etc. You had to isolate the TV chassis in order to work on it safely.

It's good practice to connect Earth, ground and protective ground at only one point.

 

[Muttley600]

ok, looking at signals
MUTT36 showing VS2 supplying neg signal
MUTT37 showing VS1 suppying pos signal
MUTT38 showing effect of on one zenner
MUTT39 showing effect of both zenners
MUTT40 showing effect of R2
MUTT41 showing effect if R1
MUTT42 seems to be the only cap (C1) making any difference, all the rest has same signal both sides
MUTT43 showing effect of R3
MUTT44 showing both sides of R5, it doesn't seem to be doing anthing?
MUTT45 showing R5 taken out with what seems like no impact
MUTT46 showing signal still the same (only number now V4 instead of V9 because I measured off R5 before)
MUTT47, so I can relate to OpAmp

So, circuit is working as follows:
- line off VS2 goes into side lead 1 & + line of VS2 into lead 4 of OP1
lead 3 is pulling VP through C2 (relating to MUTT41, with sillyscope showing a 500mV signal but multimeter showing 12.6mV, that seems confusing?) from gnd
Lead 2 is again pulling VP from gnd, through zenners (relating to MUTT38 & 39) with sillyscope showing 1V over both Z1 & Z2, although again the multimeter is showing Mutt38 as 26.16mV & MUTT39 as 75.6mV, so the zenners are not bleeding VP off but actually working the oppisite way around, bringing supply in, then coming through R2 altering VP to 42.6mV to C1 which is lowering VP to 16.6mV but over time so altering the phase of the signal giving us the VF1 signal via lead 5, so that is how OpAmp1 is working (& KISS already gave us link explaining that zenners were actually starting oscillation)
So if leads 2&3 are altering the phase, lead5 as the output, leads 1&4 giving us the required - &+ signal for waves, that means this OpAmp is not actually being used to boost the signal more so just used to alter the phase of power through it like a junction box, looking back at post #168, I even can relate to what CBB was telling me about the inverted signal now, so although there is 5V in, it is only drawing 16.6mV via resistors because that's how circuit is built, only taking power it needs

I will have a try at understanding OpAmp2 tomorrow

I'm starting to understand how this is actually all working now **broken link removed**

At this point, I'm struggling to understand why I'm getting different redings off multimeter & sillyscope but I think I'm actually starting to understand how this is working - ahhhhh, the sillyscope is just showing the range it is reading in, not actual VP inline, gottit, I havent have I, that can't be right?

Please correct me if I'm misunderstanding

 

[cowboybob]

that means this OpAmp is not actually being used to boost the signal more so just used to alter the phase of power through it like a junction box

You've gained an important insight, here. OpAmps aren't limited to amplifying!

I should add, though, that if what you want to do is boost a microphone's output, then, yes, an OpAmp can to that. But think "Operation". If what you want to do is amplify the phase shift, or wave shape, or invert from a plus to a minus potential, etc., an OpAmp can do it.

Very impressive parsing of the circuit, Graham. Also a very impressive explication of its workings.

Proud of ya...

And, yes, even more impressive that you removed R5 (would not have thought to do that) and its removal had zero effect on the circuit. Matter of fact, the cosine sig was much better looking at, for instance, VP_10 (left side of C1).

You're getting very good at this.

Here's a Neato circuit sim. site with various virtual circuits displaying current flows, o'scope presentations, etc. Needs Java, though.

First one up is an RLC circuit. Operate the switch in the circuit and observe how the current flow "charges" the inductor. Then open the switch and observe how the RLC portion "oscillates", with ever decreasing current (and voltage) levels as the cap discharges. VERY cool. Have fun.

This, circuit, by the way. does not translate into a working TINA schematic. It's a demo only. Matter of fact, that circuit blows TINA up...

But it demonstrates how, by pulsing (turning the juice on and off in a regulated fashion) a circuit like this, an oscillation can be maintained.

They have a whole catalog of circuits ("Index of circuit examples").