Re: Q. re: CircuitMaker (Student)

Kris Krieger wrote:
Joerg <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote in
news:5IKok.18171$mh5.1147@xxxxxxxxxxxxxxxxxxxx:

Kris Krieger wrote:
Hi, I'm fooling around with CircuitMaker student version. I'm
curious as to whether anyone can tell me why a battery is not both a
voltage source and a current source - I thought that current was
necessary to calculate re: powering things, so this is confusing to
me.

Also, does anyone know whether I'd therfore have to add both a
battery, and an accompanying current source...?

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.


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).


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 ;-)


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...?


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.


TIA again!

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


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.

--
Regards, Joerg

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