Re: gEDA-user: very backward time step?

[asomers@xxxxxxxxx]

In this case, the solver will not need to add extra steps internally.
You specified a sin generator, whose output is a simple function of
time, and a resistor.  The whole circuit is memoryless.  At 60Hz, the
period is just 16.6ms.  With a 10ms step size, of course you're going
to see an aliased waveform.  You must decrease your step size.

OTOH, if you add a capacitor and/or inductor to that circuit, then the
transient solver might decrease its step size automatically.  Or it
might not.  Bottom-line: decrease your step size.

On Tue, Sep 21, 2010 at 10:27 AM, Chris Cole <clecol@xxxxxxxxx> wrote:
>>
>> On Tuesday 21 September 2010, Chris Cole wrote:
>>
>>>
>>> I get a normal sine wave output,
>>> but when the frequency increases, the wave changes
>>> considerably and  starts to turn into a triangle wave...I'm
>>> not sure what I'm doing wrong, but this is strange.
>>>
>>
>> In the tran command (tran 10m 10 1) you asked it to strobe at 1
>> second intervals.  So, no matter what the signal, you get
>> samples 1 second apart.
>>
>> If you add "trace all" to the tran command you will see all of
>> the samples, which should produce a smoother waveform.
>>
>> How it works is a throwback to when people actually looked at
>> ASCII plots.  It needs to change to make "trace all" the
>> default, and have the strobe interval require a keyword "strobe"
>> like spectre does.
>>
>> The actual time stepping is determined internally.  There will
>> be extra steps internally if needed to get a proper simulation,
>> but they are not displayed unless you ask for them.
>>
>>
>>
>
> Even with the "trace all" added to my tran command:
>
> #!/bin/bash
> gnucap <<EOF
> build
> Vcc ( vin 0 ) sin offset=0. amplitude=24. frequency=60.
> r1 ( vin 0 ) 1.K
>
> list
> print tran v(Vcc)
> tran 10m 10 1 trace all > ac_test.gwave
> !gwave ac_test.gwave
> EOF
> rm ac_test.gwave
>
>
> I get a crazy waveform (attached)
>
>
> Chris
>
>
>
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>
>


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