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Qucs / qucsator

Circuit simulator of the Qucs project
http://qucs.sourceforge.net
GNU General Public License v2.0
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Convergence problem with no GND #6

Open kagiannis opened 5 years ago

kagiannis commented 5 years ago

In Qucs there is convergence problem in transient simulation when ground is not present especially for non linear components. As most new users(like me) do not specify ground as it is not mandated, I propose Qucs should display error if GND is not present.

felix-salfelder commented 5 years ago

On Sat, Nov 17, 2018 at 04:48:03AM -0800, algorithm314 wrote:

I Qucs there is convergence problem in transient simulation when ground is not present especially for non linear components. As most new users(like me) do not specify ground as it is not mandated, I propose Qucs should display error if GND is not present.

the presence of GND it neither required nor sufficient for convergence. it is clearly better not to display an error. the error is the non-convergence.

perhaps qucsator should print "notice: no components are connected to ground, this may affect convergence in some situations.", in case no components are connected to ground.

hth felix

kagiannis commented 5 years ago

Yes something should be displayed. But it is very strange that even a single diode rectifier conected to a resistor has problems with convergence. Also in my opinion the installation process of qucs is very difficult for Linux. I could only do it through source. A self contained directory will be very helpfull.

felix-salfelder commented 5 years ago

On Sat, Nov 17, 2018 at 06:12:12AM -0800, algorithm314 wrote:

Yes something should be displayed. But it is very strange that even a single diode rectifier conected to a resistor has problems with convergence.

with or without gnd? floating diodes are more tricky.. please show us the netlist.

Also in my opinion the installation process of qucs is very difficult for Linux. I could only do it through source. A self contained directory will be very helpfull.

this is off topic, please open a new issue or merge request.

(what difficulties did you encounter? what is a self contained directory?)

kagiannis commented 5 years ago

The circuit is this image and it works.But without the GND it does not work. The netlist is(including the GND)

# Qucs 0.0.19  /home/konstantinos/.qucs/test.sch

.TR:TR1 Type="lin" Start="0" Stop="100 ms" Points="100" IntegrationMethod="Euler" Order="2" InitialStep="1 ns" MinStep="1e-5" MaxIter="150" reltol="0.001" abstol="1 pA" vntol="1 uV" Temp="26.85" LTEreltol="1e-3" LTEabstol="1e-6" LTEfactor="1" Solver="CroutLU" relaxTSR="no" initialDC="yes" MaxStep="0"
Diode:D_1N4148_1 _net0 _net1 Is="222p" N="1.65" Cj0="4p" M="0.333" Vj="0.7" Fc="0.5" Cp="0" Isr="0" Nr="2" Rs="68.6m" Tt="5.76n" Ikf="0" Kf="0" Af="1" Ffe="1" Bv="75" Ibv="1u" Temp="26.85" Xti="3.0" Eg="1.11" Tbv="0.0" Trs="0.0" Ttt1="0.0" Ttt2="0.0" Tm1="0.0" Tm2="0.0" Tnom="26.85" Area="1.0"
R:R1 gnd _net0 R="50 Ohm" Temp="26.85" Tc1="0.0" Tc2="0.0" Tnom="26.85"
VProbe:Pr1 _net0 gnd
Vac:V1 _net1 gnd U="50 V" f="50 Hz" Phase="0" Theta="0"
.DC:DC1 Temp="26.85" reltol="0.001" abstol="1 pA" vntol="1 uV" saveOPs="no" MaxIter="150" saveAll="no" convHelper="none" Solver="CroutLU"

With self contained directory i mean a directory that contains all required dependencies. Like windows installation or the same as when you download firefox for Linux from the site.

As for the dificulties the packages names are not the same(for example libgd-dev instead of libgd2-xpm-dev) and adms libraries when installed where not in the PATH. Also i dont think many new users will do all the required steps.