Electronics Computer-Aided Design pspice changing time step issue

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Subject Author Date
pspice changing time step issue panfilero 03-14-08
Posted by panfilero on March 14, 2008, 8:52 am
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I have a couple issues I'm having trouble with, I'm using orcad 16 and
trying to simulate a simple circuit, it's basically two pulse
generators VPULSE each going through a diode... I'm trying to "diode-
or" two voltage sources... but I keep getting these large voltage
spikes.... say if I set the pulses at 12V I get these 16V spikes...
and then they settle to 12V here is my circuit, where V1 and V2 are 12
Volt pulses slightly offset from one another... I was especting to
seee 12 V on the Vout regardless of whether V1, V2 or both were on


V1 O-----|>|-------
D1 |
|-------------O Vout
|
V2 O-----|>|-------
D2


My other issue is, I try to set my pulses for 1 second each and then
want my simulation to go to 3 seconds, but it takes forever to run
through the simulation, does anyone know how I can speed that up....
can I change the sampling rate or something so it would fnish faster?

Much thanks
J.

Posted by MooseFET on March 14, 2008, 9:23 am
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> I have a couple issues I'm having trouble with, I'm using orcad 16 and
> trying to simulate a simple circuit, it's basically two pulse
> generators VPULSE each going through a diode... I'm trying to "diode-
> or" two voltage sources... but I keep getting these large voltage
> spikes.... say if I set the pulses at 12V I get these 16V spikes...
> and then they settle to 12V here is my circuit, where V1 and V2 are 12
> Volt pulses slightly offset from one another... I was especting to
> seee 12 V on the Vout regardless of whether V1, V2 or both were on
>
> V1 O-----|>|-------
> D1 |
> |-------------O Vout
> |
> V2 O-----|>|-------
> D2
>
> My other issue is, I try to set my pulses for 1 second each and then
> want my simulation to go to 3 seconds, but it takes forever to run
> through the simulation, does anyone know how I can speed that up....
> can I change the sampling rate or something so it would fnish faster?

Do you have a load resistor on the circuit or is the two diodes the
whole thing?

Spice sometimes gives wild results for circuits that won't work. With
no load resistor, the Vout node is basically floating when the two
diodes are off.

Posted by panfilero on March 14, 2008, 11:36 am
Please log in for more thread options
>
>
>
>
>
> > I have a couple issues I'm having trouble with, I'm using orcad 16 and
> > trying to simulate a simple circuit, it's basically two pulse
> > generators VPULSE each going through a diode... I'm trying to "diode-
> > or" two voltage sources... but I keep getting these large voltage
> > spikes.... say if I set the pulses at 12V I get these 16V spikes...
> > and then they settle to 12V here is my circuit, where V1 and V2 are 12
> > Volt pulses slightly offset from one another... I was especting to
> > seee 12 V on the Vout regardless of whether V1, V2 or both were on
>
> > =A0 =A0 =A0 =A0 =A0 =A0V1 =A0 O-----|>|-------
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0D1 =A0 =A0 =A0|
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0|=
-------------O =A0Vout
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0|=

> > =A0 =A0 =A0 =A0 =A0 =A0V2 =A0 O-----|>|-------
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0D2
>
> > My other issue is, I try to set my pulses for 1 second each and then
> > want my simulation to go to 3 seconds, but it takes forever to run
> > through the simulation, does anyone know how I can speed that up....
> > can I change the sampling rate or something so it would fnish faster?
>
> Do you have a load resistor on the circuit or is the two diodes the
> whole thing?
>
> Spice sometimes gives wild results for circuits that won't work. =A0With
> no load resistor, the Vout node is basically floating when the two
> diodes are off.- Hide quoted text -
>
> - Show quoted text -

I do have a load resistor.... and also grounds, would you expect a
voltage spike in a circuit like this?

Posted by MooseFET on March 14, 2008, 10:04 pm
Please log in for more thread options
>
>
>
>
> > > I have a couple issues I'm having trouble with, I'm using orcad 16 and
> > > trying to simulate a simple circuit, it's basically two pulse
> > > generators VPULSE each going through a diode... I'm trying to "diode-
> > > or" two voltage sources... but I keep getting these large voltage
> > > spikes.... say if I set the pulses at 12V I get these 16V spikes...
> > > and then they settle to 12V here is my circuit, where V1 and V2 are 12
> > > Volt pulses slightly offset from one another... I was especting to
> > > seee 12 V on the Vout regardless of whether V1, V2 or both were on
>
> > > V1 O-----|>|-------
> > > D1 |
> > > |-------------O Vout
> > > |
> > > V2 O-----|>|-------
> > > D2
>
> > > My other issue is, I try to set my pulses for 1 second each and then
> > > want my simulation to go to 3 seconds, but it takes forever to run
> > > through the simulation, does anyone know how I can speed that up....
> > > can I change the sampling rate or something so it would fnish faster?
>
> > Do you have a load resistor on the circuit or is the two diodes the
> > whole thing?
>
> > Spice sometimes gives wild results for circuits that won't work. With
> > no load resistor, the Vout node is basically floating when the two
> > diodes are off.- Hide quoted text -
>
> > - Show quoted text -
>
> I do have a load resistor.... and also grounds, would you expect a
> voltage spike in a circuit like this?


No I wouldn't.

What sort of diodes is it and what sort of spice?

Posted by on March 14, 2008, 11:06 am
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On 3=D4=C214=C8=D5, =CF=C2=CE=E78=CA=B152=B7=D6, panfilero <panfil...@gmail.=
com> wrote:
> I have a couple issues I'm having trouble with, I'm using orcad 16 and
> trying to simulate a simple circuit, it's basically two pulse
> generators VPULSE each going through a diode... I'm trying to "diode-
> or" two voltage sources... but I keep getting these large voltage
> spikes.... say if I set the pulses at 12V I get these 16V spikes...
> and then they settle to 12V here is my circuit, where V1 and V2 are 12
> Volt pulses slightly offset from one another... I was especting to
> seee 12 V on the Vout regardless of whether V1, V2 or both were on
>
> V1 O-----|>|-------
> D1 |
> |-------------O Vout
> |
> V2 O-----|>|-------
> D2
>
> My other issue is, I try to set my pulses for 1 second each and then
> want my simulation to go to 3 seconds, but it takes forever to run
> through the simulation, does anyone know how I can speed that up....
> can I change the sampling rate or something so it would fnish faster?
>
> Much thanks
> J.



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