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Making a Full Wave Rectified Signal in Ltspice.

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D from BC

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Nov 26, 2011, 12:19:00 AM11/26/11
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afaik it's not possible to set the 'Independent V source' alone to
create a full wave rectified signal.
It would be tidy to know for sure.

Last time I used 2 out of phase generators and 2 ideal diodes.
Simpler?

The purpose is to have a simple model of a bridge rectifier on the mains.

Greg Neill

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Nov 26, 2011, 12:51:34 AM11/26/11
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Just ground one leg of the "Independent V source' through a very, very
large resistance. The simulator is looking for a path to ground so that
it can "anchor" its calculations.


Jim Thompson

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Nov 26, 2011, 9:58:35 AM11/26/11
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V*sgn(V)

See p43 of the LTspice manual.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
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| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
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I love to cook with wine. Sometimes I even put it in the food.

Jamie

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Nov 26, 2011, 1:32:26 PM11/26/11
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Ah, don't feel bad. Last night I was dabbling around with some diode
strings in a circuit and I decided to do a jumper around them instead of
editing them out of the circuit. The jumper works fine how ever, when
you click on the diode string inside the jumper string, you get a nice
graph of loaded noise!.

I guess some one could of thought the jumper wire may act as a antenna
and the diodes were acting like detectors. That is the only thing I can
come up with why LtSPice would even bother processing them.

Jamie



John S

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Nov 26, 2011, 1:44:15 PM11/26/11
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Version 4
SHEET 1 880 680
WIRE 160 96 -16 96
WIRE -16 128 -16 96
WIRE -16 224 -16 208
FLAG -16 224 0
SYMBOL bv -16 112 R0
SYMATTR InstName B1
SYMATTR Value V=170*abs(sin (377*time))
TEXT -50 248 Left 2 !.tran 0 .1 0 10u

D from BC

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Nov 27, 2011, 3:13:02 AM11/27/11
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My favorite is leaving voltage sources loaded with nothing.
Just grounded.
Often I have many unused voltage sources on the schematic as if I had
many power supplies adjusted on the bench and connected to whichever needed.
'What was that last voltage I tried?'

D from BC

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Nov 27, 2011, 3:33:16 AM11/27/11
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Ah.. Using the arbitrary behavioral voltage source.

I would have tried degrees first.
360/period = 21600 degrees/s.

But function is set for radians.
2*pi/period = 377 radians/s.

D from BC

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Nov 27, 2011, 3:35:41 AM11/27/11
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Maybe it's cause it's late but I'm trying to make sense of that.

D from BC

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Nov 27, 2011, 3:36:20 AM11/27/11
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On 11/26/2011 6:58 AM, Jim Thompson wrote:
> On Fri, 25 Nov 2011 21:19:00 -0800, D from BC
> <myreal...@comic.com> wrote:
>
>> afaik it's not possible to set the 'Independent V source' alone to
>> create a full wave rectified signal.
>> It would be tidy to know for sure.
>>
>> Last time I used 2 out of phase generators and 2 ideal diodes.
>> Simpler?
>>
>> The purpose is to have a simple model of a bridge rectifier on the mains.
>
> V*sgn(V)
>
> See p43 of the LTspice manual.
>
> ...Jim Thompson

Will look into that. Thks.


Greg Neill

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Nov 27, 2011, 8:28:06 AM11/27/11
to
Perhaps it was my interpretation of the problem you were experiencing
that is at fault, and not your ability to comprehend my reply :-)

When I read your post I thought the issue was with the simulator
software not liking a transformer primary circuit 'floating'
without a path to ground (Typically one would like to make the gound
node coincide with the negative DC output lead).

But now I see that really you just want to have a voltage source
that produces a full-wave rectified waveform.


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