On Wed, 18 Jan 2012 19:50:22 -0500, Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:>qrk wrote: > >> On Tue, 17 Jan 2012 23:43:42 -0500, Jamie >> <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote: >> >> >>>Jim Thompson wrote: >>> >>> >>>>On Tue, 17 Jan 2012 22:32:53 -0500, Jamie >>>><jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote: >>>> >>>> >>>> >>>>>Does the wires assume real life situations to some >>>>>degree or do we need to add stray inductance, Resistors >>>>>and caps to act like a board? >>>>> >>>>> I would of thought it would assume an average lay out of one >>>>>persons worse nightmare and the actual real live circuit would >>>>>just work better, seeing that this designer would engineer proper >>>>>protocols on the board. >>>>> >>>>> It just seems that I don't see many of the small defects the >>>>>sim may show, when it is on a real board assembled using common >>>>>practices. >>>>> >>>>> Which leads me to my question, does the sim assume a worse case >>>>>scenario or maybe the sim just over exaggerates now and then? >>>>> >>>>>This would be LTspice I am referring to. I was thinking of looking at >>>>>Pspice to see how that goes. >>>>> >>>>>Jamie >>>>> >>>> >>>> >>>>Do the math... by hand... then use the sim to VERIFY! >>>> >>>> ...Jim Thompson >>> >>>Well that just sounds counter productive. >>> >>> Why waste my time using a sim if I am going to do it by hand in the >>>first place? >>> >>> You can haggle all you want Jim, It does not work on me.. >>> >>> I am not one of your goal post. You have JL for that :) >>> >>> Jamie >>> >> >> If you don't understand your circuit maths, how do you know if the >> simulation is close to reality???? Many times, you can do this in your >> head, but sometimes you need to write down a bunch of maths to >> understand issues you may run in to. As an excercise, try to >> temperature stabilize a simple one transistor amplifier without >> understanding the basic transistor equations. >> >> Do you blindly trust your models??? If you do, beware, they are often >> wrong. With experience, you will learn a healthy distrust in your >> simulator and test equipment. > >Fucking beginners > > What a gas! > >Jamie > >What a sick puppy, but I'm not surprised, since you seem to have chosen to follow Larkin as your mentor. ...Jim Thompson -- | James E.Thompson, CTO | 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 | I love to cook with wine. Sometimes I even put it in the food.
Still waiting for a Ltspice expert answer.
Started by ●January 17, 2012
Reply by ●January 18, 20122012-01-18
Reply by ●January 18, 20122012-01-18
Jim Thompson wrote:> On Wed, 18 Jan 2012 19:50:22 -0500, Jamie > <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote: > > >>qrk wrote: >> >> >>>On Tue, 17 Jan 2012 23:43:42 -0500, Jamie >>><jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote: >>> >>> >>> >>>>Jim Thompson wrote: >>>> >>>> >>>> >>>>>On Tue, 17 Jan 2012 22:32:53 -0500, Jamie >>>>><jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote: >>>>> >>>>> >>>>> >>>>> >>>>>>Does the wires assume real life situations to some >>>>>>degree or do we need to add stray inductance, Resistors >>>>>>and caps to act like a board? >>>>>> >>>>>>I would of thought it would assume an average lay out of one >>>>>>persons worse nightmare and the actual real live circuit would >>>>>>just work better, seeing that this designer would engineer proper >>>>>>protocols on the board. >>>>>> >>>>>>It just seems that I don't see many of the small defects the >>>>>>sim may show, when it is on a real board assembled using common >>>>>>practices. >>>>>> >>>>>>Which leads me to my question, does the sim assume a worse case >>>>>>scenario or maybe the sim just over exaggerates now and then? >>>>>> >>>>>>This would be LTspice I am referring to. I was thinking of looking at >>>>>>Pspice to see how that goes. >>>>>> >>>>>>Jamie >>>>>> >>>>> >>>>> >>>>>Do the math... by hand... then use the sim to VERIFY! >>>>> >>>>> ...Jim Thompson >>>> >>>>Well that just sounds counter productive. >>>> >>>>Why waste my time using a sim if I am going to do it by hand in the >>>>first place? >>>> >>>>You can haggle all you want Jim, It does not work on me.. >>>> >>>>I am not one of your goal post. You have JL for that :) >>>> >>>>Jamie >>>> >>> >>>If you don't understand your circuit maths, how do you know if the >>>simulation is close to reality???? Many times, you can do this in your >>>head, but sometimes you need to write down a bunch of maths to >>>understand issues you may run in to. As an excercise, try to >>>temperature stabilize a simple one transistor amplifier without >>>understanding the basic transistor equations. >>> >>>Do you blindly trust your models??? If you do, beware, they are often >>>wrong. With experience, you will learn a healthy distrust in your >>>simulator and test equipment. >> >>Fucking beginners >> >> What a gas! >> >>Jamie >> >> > > > What a sick puppy, but I'm not surprised, since you seem to have > chosen to follow Larkin as your mentor. > > ...Jim ThompsonActually, I think Larkin is a smart Dude! I take my hat to him for his offerings he has made here, despite all the interference. Jamie
Reply by ●January 18, 20122012-01-18
On Wed, 18 Jan 2012 20:12:28 -0500, krw@att.bizzzzzzzzzzzz wrote:> On Tue, 17 Jan 2012 23:23:30 -0600, Tim Wescott <tim@seemywebsite.com> > wrote: > >>On Tue, 17 Jan 2012 22:32:53 -0500, Jamie wrote: >> >>> Does the wires assume real life situations to some degree or do we >>> need to add stray inductance, Resistors and caps to act like a board? >>> >>> I would of thought it would assume an average lay out of one >>> persons worse nightmare and the actual real live circuit would just >>> work better, seeing that this designer would engineer proper protocols >>> on the board. >>> >>> It just seems that I don't see many of the small defects the >>> sim may show, when it is on a real board assembled using common >>> practices. >>> >>> Which leads me to my question, does the sim assume a worse case >>> scenario or maybe the sim just over exaggerates now and then? >>> >>> This would be LTspice I am referring to. I was thinking of looking >>> at >>> Pspice to see how that goes. >> >>Wires in LTSpice (and PSpice, as far as I know), are made of Magic >>Stuff. A node is a node is a node (in Spice-land) and has no voltage >>variations across it. > > That's true (with LTSpice) but all connections on a wire are not equal. > You can measure the current in a wire at any place along the wire. > LTSpice looks left and right from that point to get the current at that > point. The topology matters.Well, that's what I hoped he'd get -- wires in LTSpice are made of magic stuff, wires in this humdrum mundane world we live in are made of real stuff. If you want to simulate the real stuff with the magic stuff, you need to add detail to your simulation.>>Jim's right, although I would state it differently: the simulation is >>help for those who already know what's up; try something that the >>simulation isn't prepared to give a correct answer for, and you'll get a >>wrong answer. > > Like transmission line speed > C. ;-) > >>It _is_ handy for complex, nonlinear circuits (like switchers), but you >>still have to pose questions that it can answer sensibly. > > It's also handy for statistical or worst-case analysis on complex > designs.True, although even there you can often go much farther with pencil & paper methods than most folks go. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Reply by ●January 18, 20122012-01-18
On Wed, 18 Jan 2012 19:51:31 -0600, Tim Wescott <tim@seemywebsite.com> wrote:>On Wed, 18 Jan 2012 20:12:28 -0500, krw@att.bizzzzzzzzzzzz wrote: > >> On Tue, 17 Jan 2012 23:23:30 -0600, Tim Wescott <tim@seemywebsite.com> >> wrote: >> >>>On Tue, 17 Jan 2012 22:32:53 -0500, Jamie wrote: >>> >>>> Does the wires assume real life situations to some degree or do we >>>> need to add stray inductance, Resistors and caps to act like a board? >>>> >>>> I would of thought it would assume an average lay out of one >>>> persons worse nightmare and the actual real live circuit would just >>>> work better, seeing that this designer would engineer proper protocols >>>> on the board. >>>> >>>> It just seems that I don't see many of the small defects the >>>> sim may show, when it is on a real board assembled using common >>>> practices. >>>> >>>> Which leads me to my question, does the sim assume a worse case >>>> scenario or maybe the sim just over exaggerates now and then? >>>> >>>> This would be LTspice I am referring to. I was thinking of looking >>>> at >>>> Pspice to see how that goes. >>> >>>Wires in LTSpice (and PSpice, as far as I know), are made of Magic >>>Stuff. A node is a node is a node (in Spice-land) and has no voltage >>>variations across it. >> >> That's true (with LTSpice) but all connections on a wire are not equal. >> You can measure the current in a wire at any place along the wire. >> LTSpice looks left and right from that point to get the current at that >> point. The topology matters. > >Well, that's what I hoped he'd get -- wires in LTSpice are made of magic >stuff, wires in this humdrum mundane world we live in are made of real >stuff. > >If you want to simulate the real stuff with the magic stuff, you need to >add detail to your simulation. > >>>Jim's right, although I would state it differently: the simulation is >>>help for those who already know what's up; try something that the >>>simulation isn't prepared to give a correct answer for, and you'll get a >>>wrong answer. >> >> Like transmission line speed > C. ;-) >> >>>It _is_ handy for complex, nonlinear circuits (like switchers), but you >>>still have to pose questions that it can answer sensibly. >> >> It's also handy for statistical or worst-case analysis on complex >> designs. > >True, although even there you can often go much farther with pencil & >paper methods than most folks go.Perhaps, but doing statistics on 100,000 cases isn't much fun by hand. ;-)
Reply by ●January 19, 20122012-01-19
On Wed, 18 Jan 2012 02:42:37 -0800, Robert Macy wrote:> And, oh, yes, don't forget to add that even > peskier term, "radiation loss" That way when you simulate charging a > cap from another cap, you can reconcile the apparent loss of energy.Please, pretty please, don' open that can of worms again. It was talked to death some time ago ;-) -- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)
Reply by ●January 19, 20122012-01-19
On Thu, 19 Jan 2012 11:53:32 -0800, Fred Abse <excretatauris@invalid.invalid> wrote:>On Wed, 18 Jan 2012 02:42:37 -0800, Robert Macy wrote: > >> And, oh, yes, don't forget to add that even >> peskier term, "radiation loss" That way when you simulate charging a >> cap from another cap, you can reconcile the apparent loss of energy. > >Please, pretty please, don' open that can of worms again. It was talked to >death some time ago ;-)[smirk] ...Jim Thompson -- | James E.Thompson, CTO | 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 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●January 20, 20122012-01-20
The model is the RLCG model for transmission lines. R = resistance L = inductance C = capacitance G = conductance The R and L are in series with the line. The c and G are in parallel. These parameters are on a per-meter basis, multiply by the length dz to obtain the total element value in ohms, henries, farads and siemens. Look at Gayle Miner's book: Lines and Electromagnetic Fields for Engineers. p10-14 HTH, Dave
Reply by ●January 20, 20122012-01-20
On Fri, 20 Jan 2012 08:16:26 -0800, David Hutchinson wrote:> > The model is the RLCG model for transmission lines. > > R = resistance > L = inductance > C = capacitance > G = conductance > > The R and L are in series with the line. The c and G are in parallel. > These parameters are on a per-meter basis, multiply by the length dz to > obtain the total element value in ohms, henries, farads and siemens. >Most, if not all Spice do not fully implement an RLCG model. The lossy line model, LTRA, only implements R, L, and C. Nonzero G not supported (yet). The parameters are on a *per-unit* basis, not per-meter, allowing the use of feet, inches, millimeters, cubits, parsecs, whatever. Examples: .model RG223 LTRA (LEN=1 R=11.3m L=0.077u C=30.8p) .model RG59 LTRA (LEN=1 R=51.6m L=0.115u C=20.5p) Units in this case are per foot. -- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)
Reply by ●January 20, 20122012-01-20
On Fri, 20 Jan 2012 11:19:40 -0800, Fred Abse <excretatauris@invalid.invalid> wrote:>On Fri, 20 Jan 2012 08:16:26 -0800, David Hutchinson wrote: > >> >> The model is the RLCG model for transmission lines. >> >> R = resistance >> L = inductance >> C = capacitance >> G = conductance >> >> The R and L are in series with the line. The c and G are in parallel. >> These parameters are on a per-meter basis, multiply by the length dz to >> obtain the total element value in ohms, henries, farads and siemens. >> > >Most, if not all Spice do not fully implement an RLCG model. The lossy >line model, LTRA, only implements R, L, and C. Nonzero G not supported >(yet). > >The parameters are on a *per-unit* basis, not per-meter, allowing the use >of feet, inches, millimeters, cubits, parsecs, whatever. > >Examples: > >.model RG223 LTRA (LEN=1 R=11.3m L=0.077u C=30.8p) > >.model RG59 LTRA (LEN=1 R=51.6m L=0.115u C=20.5p) > >Units in this case are per foot.PSpice has a full RLCG model... "TLOSSY" in the parts index. ...Jim Thompson -- | James E.Thompson, CTO | 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 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●January 20, 20122012-01-20
On Fri, 20 Jan 2012 13:07:00 -0700, Jim Thompson wrote:> PSpice has a full RLCG model... "TLOSSY" in the parts index.Didn't know that. LTspice *appears* to have, then you try to use G, and it tells you to go away. It appears to be code lifted straight out of Berkeley Spice 3. -- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)
