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Old 17th February 2007, 04:53 AM   #1
Wizard of Kelts
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Default Help Putting XFormers In Spice Please

I just started Spice a couple of days ago, because I have a vague idea for a XFormer circuit and wanted to work it out. I have a deadline of sorts for the prototype of this project, (not a work deadline, I'm not in the field), and would greatly appreciate help on how to put these X formers into Spice and get them mutually coupled so I can proceed with my simming. Most everything else I am doing seems to be coming naturally, just getting these X Formers entered is giving me problems.

I am interested in audio Xformers, and here the primary is 25H, and the secondary has 4 times the voltage as the primary.

Any help is appreciated.

First, a center tapped X former.
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File Type: gif center tapped transformer.gif (3.5 KB, 241 views)
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Old 17th February 2007, 05:00 AM   #2
Wizard of Kelts
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Next is two different unconnected secondary windings, except that they can be hooked up at will.

The entire two secondary windings add up to 4 times the voltage as the primary. Again, the primary is 25H. The bottom secondary has a 1: voltage ratio with the primary, the top secndary has a 3:1 voltage ratio to the primary.

I greatly appreciate whatever help I can get. I am finding the LT program somewhat intuitve once you get past the first steps, but I have a deadline on this XFormer prototype.
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File Type: gif transformers 1.gif (3.5 KB, 222 views)
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Old 17th February 2007, 06:43 AM   #3
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A transformer is 2 or more coupled inductors. The FAQs section of the LTspice help file has information on this.
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Old 17th February 2007, 07:48 AM   #4
Netlist is offline Netlist  Belgium
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I hope this will help.

http://www.cox-internet.com/wa5bdu/ltguide.doc

spice model for UL output transformer?

/Hugo
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Old 17th February 2007, 06:08 PM   #5
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When you use the inductors in LTSpice/SWCAD use the parasitic parameters for winding resistance and capacitance for each L. This minimizes the number of nodes in your circuit and makes the simulations run faster. It doesn't matter much for small circuits, but if they start getting complex, it can help a lot.

I_F
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Old 19th February 2007, 12:28 AM   #6
jcx is offline jcx  United States
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Yahoo Groups LtSpice is the best resource, you have to join since its members only

in the LtSpice Group: Files > Lib > Linear Transformers

there are examples with subcircuits and symbols:

Click the image to open in full size.

but such elaboration is unnecessary (you have to add .asy to your lib\sym\misc folder, the subcircuit .txt to lib\sub folder)

just put your 3 inductors on the schematic with the turns ratio determining the inductance ratios - if pri L1 = 25 H and secondary L2 is supposed to have 2x pri truns ratio then L2 = (2)^2 * 25 H = 100 H, with L3 = 100 H also you have your "center tapped 4:1 secondary"

to complete the association of L1, L2, L3 as a transformer you need to add the spice directive for the coupling factor to your schematic (far right on tool bar ".op" button)

open <.op> edit box, add text:

K123 L1 L2 L3 0.999

put it on shcematic page with L1, L2, L3
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Old 21st February 2007, 04:46 AM   #7
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So far, I am making musch, much progress on this project, thanks to the extremely helpful answers on this and other threads on diyaudio.

I have a circuit which might work, but I have been using an 8 ohm resistor as a load. I am interested primarily in vented boxes, some closed boxes too.

I have taken a netlist from Microcap for a vented box speaker, and would like to use the vented box as a load for my circuit.

Here is the Netlist. How do I put this into LT Spice to use as a load?

VENTED-BOX NETLIST
*DISPLAY VM(1)/IM(VD1) FOR INPUT IMPEDANCE
*DISPLAY VM(21) FOR DIAPHRAGM DISPLACEMENT
*DISPLAY VM(22) FOR PORT DISPLACEMENT
*DISPLAY 20*LOG10(VM(23)) FOR ON-AXIS PRESSURE
*DISPLAY 20*LOG10(VM(24)) FOR DIAPHRAGM PRESSURE
*DISPLAY 20*LOG10(VM(25)) FOR PORT PRESSURE
*ELECTRICAL CIRCUIT
VEG 1 0 AC 1V
REW 1 2 ?
*LOSSY VOICE-COIL INDUCTANCE
GRA 2 3 LAPLACE {V(2,3)}={1/(?*PWR(S,?))}
HBLUW 3 4 V2W ?
V1W 4 0 AC 0V
HBLIW 5 0 V1W ?
LMMDW 5 6 ?
RMSW 6 7 ?
CMSW 7 8 ?
ESDPW 8 9 17 10 ?
V2W 9 0 AC 0V
FSDUW 10 17 V2W ?
LMABW 10 11 ?
CABW 11 12 ?
V3W 0 12 AC 0
RALW 11 0 ?
LMAP 11 13 ?
FKP 15 13 V6W ?
LMA1P 13 15 ?
RA1P 13 14 ?
CA1P 13 14 ?
RA2P 14 16 ?
V4W 15 16 AC 0V
V5W 16 0 AC 0V
FKWUP 19 17 V4W ?
LMA1W 17 19 ?
RA1W 17 18 ?
CA1W 17 18 ?
RA2W 18 20 ?
V6W 19 20 AC 0V
V7W 20 0 AC 0V
*DIAPHRAGM DISPLACEMENT SOURCE
EXD 21 0 LAPLACE {I(V2W)}={1/S}
*PORT DISPLACEMENT SOURCE
EXP 22 0 LAPLACE {I(V5W)}={1/(?*S)}
*ON-AXIS PRESSURE SOURCE
EPSUM 23 0 LAPLACE {I(V3W)}={9390*S}
*DIAPHRAGM PRESSURE SOURCE
EPD 24 0 LAPLACE {I(V7W)}={9390*S}
*VENT PRESSURE SOURCE
EPV 25 0 LAPLACE {I(V5W)}={9390*S}
.AC DEC 100 10 10K
.PROBE
.END
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Old 21st February 2007, 04:51 AM   #8
Wizard of Kelts
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For good measure, here is the closed box netlist. How do I put this into LT Spice so I can recall it and use the loudspeaker part for my load?

I got both netlists from this Georgia Tech website, courtesy the famous Marshall Leach.

CLOSED-BOX NETLIST
*DISPLAY VM(1)/IM(VD1) FOR INPUT IMPEDANCE
*DISPLAY 20*LOG10(16) FOR ON-AXIS PRESSURE
*DISPLAY VM(17) FOR DIAPHRAGM DISPLACEMENT
*ELECTRICAL CIRCUIT
VEG 1 0 AC 1V
RE 1 2 ?
*LOSSY VOICE-COIL INDUCTANCE
GZE 2 3 LAPLACE {V(2,3)}={1/(?*PWR(S,?))}
HBLUD 3 4 VD2 ?
VD1 4 0 AC 0
*MECHANICAL CIRCUIT
HBLI 5 0 VD1 ?
LMMD 5 6 ?
RMS 6 7 ?
CMS 7 8 ?
ESDPD 8 9 10 13 ?
VD2 9 0 AC 0
*ACOUSTICAL CIRCUIT
FSDUD 13 10 VD2 ?
LMA1 10 12 ?
RA1 10 11 ?
RA2 11 12 ?
CA1 10 11 ?
VD3 12 0 AC 0
LMAB 13 14 ?
RAB 14 15 ?
CAB 15 0 ?
RAL 15 0 ?
*ON-AXIS PRESSURE DISPLAYS IN PROBE WITH 20*LOG10(VM(16))
EXP 16 0 LAPLACE {I(VD3)}={59E3*S}
*DIAPHRAGM DISPLACEMENT DISPLAYS IN PROBE WITH VM(17)
EXD 17 0 LAPLACE {I(VD2)}={1/S}
.AC DEC 50 10 10K
.PROBE
.END
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Old 21st February 2007, 05:23 AM   #9
gootee is offline gootee  United States
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Quote:
Originally posted by kelticwizard
So far, I am making musch, much progress on this project, thanks to the extremely helpful answers on this and other threads on diyaudio.

I have a circuit which might work, but I have been using an 8 ohm resistor as a load. I am interested primarily in vented boxes, some closed boxes too.

I have taken a netlist from Microcap for a vented box speaker, and would like to use the vented box as a load for my circuit.

Here is the Netlist. How do I put this into LT Spice to use as a load?

.END
It is a very good idea that you have had, to try to use a spice model of a speaker/box as your load, for simulations. It doesn't make much sense, to me, to use an 8 Ohm resistor as the model, when the responses can be (and usually are) QUITE different, when a loudspeaker model is used instead of a simple resistor.

About the only time I use a resistor as the spice model for an audio amplifier's load, nowadays, is when I want to check my squarewave response into 2.2uF || 8 Ohms.

As long as you're modeling the speaker/box, maybe you ought to also model the cables that go to it.

I found a spice speaker model, and several cables' model parameters, at: http://sound.westhost.com/cable-z.htm . It's worth a read.

There are also some spice speaker models at:

http://www.stereophile.com/reference/60/

and

http://www.pcabx.com/product/amplifiers/index.htm (4 Ohms)

There are also discussions within diyAudio.com, about modeling speakers (and speaker cables). You could do some searches and find them. I found the last two models mentiond above, that way.

Also, in the Files section of the LT-Spice discussion group, at http://www.yahoogroups.com (I HIGHLY-recommend joining that discussion group!), there is a spice speaker model, and some comments about its derivation, in a section called Adventures with Analog, by one of the geniuses who frequent that forum (analogspiceman). If I recall correctly, it also had an output in units of sound pressure. However, it's been a long time since I looked at it. And it was still a "work in progress", back then.

I don't know anything much about trying to import a microcap model into LT-SPice. You could ask in the yahoogroups forum.

All of the spice speaker models that I referenced above have been made in circuit schematic form, using inductors, capacitors, and resistors. So the method of using them with LT-SPice is obvious. They are part of the circuit.

Good luck!

- Tom Gootee

http://www.fullnet.com/~tomg/index.html

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Old 21st February 2007, 01:02 PM   #10
Wizard of Kelts
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Goatee:

Thanks for the kind words about finally modelling a loudspeaker schematic instead of an 8 ohm load. You see, this is my first Spice project, I am doing this because I have an idea for a circuit using transformers, I didn't start it just to learn to use Spice. So I started out using the 8 ohm load just to get my feet wet that my circuit would actually give a voltage reading close to what i wanted, (it now does), and figured I would now graduate and insert an actual loudspeaker schematic in there to see how it would really work.

I got the pbx loudspeaker copied and put into a separate file. Now, I have my circuit model in one file, without load. I have the pbx loudspeaker schematic in another file, and asc file.

HOW do I get the pbx file-a separate file-into my circuit file as the load? How do I get it to "cross files", so to speak?

I tried using the move feature, but it doesn't allow you to click on the top with your cursor. In short,I am looking to perform the same function that "copy"and "paste" does in a word or image processor. How do I do that?
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