Q. re: CircuitMaker (Student)

I don't know what CircuitMaker is but simulators usually assume a battery to be a perfect (meaning hard) voltage source. If needed a little resistor is added to simulate the impedance, very important for designs that use wimpy coin cells.

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A current source provides a *constant current* into a load, (ideally) regardless of what that load is.

A voltage source (or battery) will provide whatever current the load requires. So while the battery is providing a current, it is not a constant current source, as the current won't be the same with different loads.

A voltage source provides a *constant voltage* into a load, (ideally) regardless of what that load is. A real battery is a voltage source with an internal series resistance. I can't remember how CircuitMaker actually treats a battery symbol, best to use a proper constant voltage source if that's what you really want.

So a battery (or anything else) can't be both a constant voltage source and a constant current source at the same time, they are mutually exclusive.

Not together as the same source, no. You usually use either a voltage source or a current source depending upon the sub-circuit you are trying to simulate.

Dave.

Your response made me wonder what an [ideal voltage/ideal current source] device would look like:

Battery in series with iforward-biased deal diode, both in parallel with current source?

But it only works in one direction.

-Le Chaud Lapin-

Joerg wrote in news:5IKok.18171$ snipped-for-privacy@nlpi067.nbdc.sbc.com:

I Googled "hard voltage source" - so that is a voltage source with zero eries resistance (which would explain why you mentioned adding a resistor)...?

I had downloaded a few circuit design+simulator programs, and Circuit Maker is just one of those - it's by no means a professional-level orogram, I mostly just wanted something to get me going (circuit simulator programs are recommended by "Practical Electronics for Inventors", which is how I heard of them in the first place). One of the programs doesn't even have a battery symbol, and so far, none has any Solar Cell widgets, tho' it seems that one can use a "voltage in" symbol; I just started playing with Circuit Maker day before yesterday :o

Anyway, what I figured I'd do was try to set up a basic circuit from online for a solarcell-battery-LED setup. But I can't figure out yet whether I merely haven't yet figured out how to include current, or whether the simulator actually doesn't take current into account. If the latter, could that be because current determnies *rate* of battery discharge, whereas maybe the simulator only looks at voltage...?

I know this is a really basic question bordering on stupid, OTOH I guess everyone has to start at Zero, and I'm doing that very much later in life than do the hard-coe electronics hobbyists (I mean that ina complimentary manner, not to be snotty).

SO, in a simulator (the ones I downloaded are based on "Spice"), is it that one can either have voltage, *or* current, but not both...?

TIA again!

- Kris (Who prob. needs to find a "Simulators for Dummies" reference =:-o !)

"David L. Jones" wrote in news: snipped-for-privacy@k36g2000pri.googlegroups.com:

Oh...oh!, OK, because current is a function of voltage *and* resitance...?

Because no material is resistence-free, right? Whcih would be the reason for Joerg's note that "If needed a little resistor is added to simulate the impedance", right?

(Yes, I'm still in the Dummy stage... =:-o )

It has a symbol that looks like the standard Battery symbol in hte electronics texts, and you can choose to have the + and the - shown (good for us beginners ;) ), plus you can specify teh VOlts. THe Default is

10V, but you can right-click and change that parameter to, say, 1.2V, which is what I'm fooling with.

OK, as I speculated in reply to Joerg, current changes because it's a function of Volts and Resistence?

Maybe what I need to do is keep looking through my Google search (I'm currently running a search of "SPICE" AND (electronic OR electronics) and look for refernece materials, becasue I'm starting to think that the current-voltage question is both a fundamental and a peculiarity of the software structure and how it handles Power (watts). What's confusing me with the simulator is I finally understood, after some helpful explanations by folks in the "basics" NG, that *Power* In has to equal

*Power* Through/Out, so, a subcircuit can "finagle" amperage and "convert" it into voltage, or visa versa, but in the end, Watts Equals Watts (did I mention I was starting from Zero with tryign to learn some electronics...?) ANyway, so I thought I could use a simulator to analyse a simple circuit in a ways that follows that rule.

I'm Googling ("SPICE" AND (electronic OR electronics)) and looking for tutorials, references, and so on, so maybe I ought to do that first, since I'm starting to think that I ahve soem fundamental confusion re: what "Spice" is actually supposed to do.

Thank you for the info!

- Kris

Le Chaud Lapin wrote in news:9dcbb743-9814-47a6- snipped-for-privacy@26g2000hsk.googlegroups.com:

This will be a stupid Q. I'm sure, but, doesn't a circuit have to work in only one direction...?

- Kris

Might I suggest that you learn electronics at a pencil-and-paper level BEFORE going anywhere near a simulator?

...Jim Thompson

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| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Diplomacy:  Kissing ass when we should be kicking ass.

Our reliance on computers is scary these days.

A few months ago, I had to write a message on a piece of paper, and I started to write...and I could not! I tried severals time and kept goofing up. Then I thought, "Maybe switching to cursive will help..."And I forgot how to write a "B" in cursive. I had seen a German ess-tsett recently, so I tried tha, but it didn't look right. :| The pretty young woman who waiting just sat there patiently looking over my chicken scratch. I was sooo embarrassed and starting to perspire!

I looked up and said, "Look...I'm not an idiot...I do know how to write.. it's just something is wrong...and I don't know what it is."

I think it was the computer that I using to type this message. :D

-Le Chaud Lapin-

Hmm..that's tricky question.

It does help to think of a circuit driven by a DC cell as moving current in one direction. But from a theoretic point of view, there are no restrictions on V(t) and I(t). They could both be sine functions, for example.

Incidentally, since you are getting into electronics..I humbly offer a small piece of advice:

Pay close attention to your charge distributions and field distributions, meaning, when you get the time, place battery across RC circuit, and ask yourself what the charges are doing, and where they are going. You should practice doing this with increasingly complicated circuits until you can give a qualitative (not quantitative) explanation of how the charge is behaving. The PN junction and MOS capacitors are ultimate playing grounds for this game.

There is a legend that there is a professor who did this very early in his career, and after a while, he could connect transistors and diodes in all kinds of highly-unorthodox configurations and still explain how circuit would behave (when/where saturation would occur, etc.) Not a lot of engineers can do that, but many can readily analyze an emitter- follower circuit.

The math is important, but intuition charge and field distrbutions opens an entirely new world.

-Le Chaud Lapin-

Le Chaud Lapin wrote in news: snipped-for-privacy@d45g2000hsc.googlegroups.com:

Yowza... I think I'd better start by assuming the current; flows from + to - and electrons flow from - to + , which is about all my brain can handle at this point =:-o !

THanks :) - hopefully, I'll be able to learn enough to get that far! I ddi well in biology and graduated in bacteriology, but I'm more of a right-brained type and the more math-oriented sciences have always been my boogeymen. OTOH, as the saying goes, "nothing ventured, nothing gained", so I'm venturing ;)

Wow...and here I thought I was doing great when I finally understood "when a small charge goes through thsi wire, then charge/curent will flow through the other two wires" That professior must have had a natural talent...impressive!

I'll be happy if I can understand my solar light project =:-o (Trying to mesh battery-chrging IC and LED driver, to light 4-6 LEDs...I thought I could just stick together 2 smmple circuits from Maxim's application notes, but ended up realizing that nope, I first have to go back and actually learn some electronics before I can fiddle with example circuits - yup, once again, "You khve to know enough to realize what you don't know")

Baby steps first :) Although I've always had a weird fascination for the whole quantum/orbitals bit - except I can't do Calculus; I've tried numerous times, but even when I can understand what is being done in the text, I can't do it for myself. So I can only see the concepts, with the mofe exquisite details always dancing beyond my grasp. But I'm working on teh basics, Ohm's law, and the other "freshman" things - first things first ;)

THanks again,

- Kris

Le Chaud Lapin wrote in news:ee155da4-7e70-4f45- snipped-for-privacy@s50g2000hsb.googlegroups.com:

My book recommended it, tho', so I figured I'd give it a go.

Heh.

innews: snipped-for-privacy@k36g2000pri.googlegroups.com:

Correct! Start with simple "linear" loads like a resistor and a DC source that you can analyse with ohms law. Electronics starts with learning to apply ohms law and Kirchhoff's laws like 2nd nature. Don't start using a simulator until you know the basics inside and out.

Other loads and AC sources are the next step and will get more complicated, and that's where the simulator might start to help you out.

Correct. Many people make the mistake of using a simulator which can often use "ideal" components. Then they are shocked when their circuit does not work when they actually build it for real. Take the battery for example. Not only does a practical battery has a series impedance (or resistance, make sure you learn the difference), but that impedance changes as the battery discharges and also changes with temperature.

In fact it's worse than that - not only are components not "ideal" in practice but the way you construct the circuit in real life (on a printed circuit board for example) can have a massive effect upon the circuit operation.

Simulators can be BIG traps - beware. That's why you'll probably get a lot of experienced guys warning you not to use them.

Correct again. This is ohms law at work, learn it like the back of your hand.

I think you'd be best to avoid simulators until you have a better grasp on the basics. Pen, paper, calculator, breadboard, multimeter and lots of good beginner books is what's needed (more than one because you won't "click" with all of them). The simulator will never replace the breadboard and multimeter, you'll learn a lot a lot of useful practical stuff using actual hardware. But simulators do provide an easy and quick means to modify circuits and measure stuff that would otherwise take a lot of time and expensive equipment.

Welcome to the world of electronics, have fun.

Dave.

innews: snipped-for-privacy@k36g2000pri.googlegroups.com:

[snip] [snip]

I've always considered myself lucky to have been schooled B.C. (before CAD).

I didn't start using simulators until around 1980, and was appalled at the non-physical results they often spewed out.

Turns out that most of the simulator errors weren't directly a fault of the simulator, but were the result of poor modeling of (in particular) semiconductor devices.

Things have improved over the years, but I'm still wary... preferring to "noodle" ideas on paper _before_ committing to the simulator... you might look at the simulator as my "debug" tool.

No one has commented on my new SIG addition (below), but I added it as a reminder to myself that even the "great one" can waltz right into a super gotcha when you get complacent... as I did over the past several weeks ;-)

Fortunately my stringent testing routines (over all process corners) caught it before it was committed to silicon.

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
  My simulation, struggling to converge, is telling me something
    Maybe my idea of a ring of current mirrors is flawed ?:-)

"David L. Jones" wrote in news: snipped-for-privacy@i20g2000prf.googlegroups.com:

Uh-oh, some Kirchhof's examples were what I was going to try once I got the basic functions of the program figured out. I have to look at some more sources, becasue one problem with "Practical Electronics for Inventors" is that I can't figure out the explanations of how to analyse complex circuits - I'm looking throuh a few other refrences, but was hoping that Circuit Maker woudl help me out.

Woo-hoo!, OK, two more things :)

True, tho' I'll be sticking with simple things, and work with the general pronciple that "batteries discharge and die", and hopefulyl be able to figure otu the battery charging IC circuit I've been staring at ;) Believe me, there is no EE on the planet who will *ever* have to worry abotu any competition from me But I defnintely do want to understand at least the basics, and perhaps put together a few DC toys so to speak ;)

Goo0d reminder - I do recall that, for example magnetif fields ca be (? always are?) created by current flow, and that a magnetic field in one place can interfere with current flow elsewhere if the wire is too close to the magnetism. I figure that my book will deal with that in later chapters. ((I've only gotten to capacitance so far, and am taking a "side-road" into teh software.))

That's sort of a bummer, then. But it should work OK for the simple things, as a learning aid...

[snip]

I'm still taking baby-steps for now, this is definitely my weak area so it's slow going, but it's alwasy interesting to expand one's horizons.

I do appreciate the info tho' - thanks again!

- Kris

innews: snipped-for-privacy@i20g2000prf.googlegroups.com:

I can recommend Circuit Theory and Techniques by Hans Goodman (multiple volumes). But probably out of print and hard to get these days though.

Sounds like you have your head on your shoulders the right way around and are going through the right motions, so simulators should be a great verification aid for you, so don't let anyone discourage you in that respect.

Pen, paper and calculator is still better for the really simple stuff, leave the simulator for the harder and more interesting stuff!

Dave.

"David L. Jones" wrote in news: snipped-for-privacy@p31g2000prf.googlegroups.com:

1988 - I googled it; not available. [edited]

Well, sometimes my head points in the right direction ;) Mostly, I just thought I'd try the tool recommended by the book I'm currently working with.

Well pencil'n'paper is certainly more convenient - no learning curve for using them. And highly portable (even useful in waiting rooms )

Foreward Ho!

- Kris

That's only due to the fact no one had a big enough abacus when you were young. By the time they figured out how to fix all of the problems, someone else had invented the computer. ;-)

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We all started at some point in life and age shouldn't matter. Well, as long as your wife doesn't object to the lengthy "don't bother me, I'm soldering" episodes ;-)

Right, you can't have both but you can insert V-sources and I-sources at different points in your circuit. If you clump them together in one place chances are it ain't going to be happy and an error message comes up. In the old days your PC just froze up and all you had was that hunch of "I think that last change wasn't very kosher". Some simulators such as LTSpice let you select a source resistance in a voltage source, others don't. I prefer the old-fashioned way of the separate resistor because then I can always see it, less of a chance to forget to change it.

LTSpice has a pretty good tutorial and there is a Yahoo forum. IIRC it is unfortunately not mirrored into a newsgroup format like the MSP430 forum.

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Regards, Joerg

http://www.analogconsultants.com/

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Joerg wrote in news:_ehpk.17880$ snipped-for-privacy@nlpi064.nbdc.sbc.com:

[edited for length]

AH, OK, knowing that they can be inserted helps a lot, thanks!

I'm assuming it is just a peculiarity of how the algorithms were set up. I'm guessing that perhaps the idea is, you don't know how much current exists until you also have a value for resistance , and if the spice program(s) work on the assumption that a voltage source has zero resistence (?because differnt voltage sources would have different internal resistence?, so the program can't keep track of any and all potential sources?), maybe it makes more sense for the program to be set up so that V and I are treated separately.

I found something called LTSpiceSwitcherCAD, but so far, its useage is opaque to me. I'm also fooling around with somethign called SuperSpice. (These are of course rather basic programs - I only need Student-level functions, so I went for the FreeWare (or at least free for non- commercial use). So far, I like CircuitMaker because so far seems to be easy and intuitive to use (to me at least), and SuperSpice because it seems to have more options although that is hard to say right now.

If you (or others ;) ) think there would be any interest, I can post additional comments as I experiment with these some more.

OK, thank you - I'll look into those as well :)

- Kris