# Spice

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#### kinarfi

##### Well-Known Member
Would someone please plug this into spice and show me what happens?
Notice the frequencies.
Thanks
Kinarfi
Someday, I'll have to learn Spice

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#### blueroomelectronics

##### Well-Known Member
Someday, I'll have to learn Spice
Sounds like today would be good.

#### kinarfi

##### Well-Known Member
Sounds like today would be good.
Yesterday would have been better!!, but I haven't yet. so will do it for me today? Please
Thanks,
Kinarfi

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#### crutschow

##### Well-Known Member
Load LTSpice and give it a try. You won't learn much if you have someone else do it. We're not here to do your work but, if you have problems, we're here to help.

#### kinarfi

##### Well-Known Member
Sounds like today would be good.
Load LTSpice and give it a try. You won't learn much if you have someone else do it. We're not here to do your work but, if you have problems, we're here to help.
You guys are correct, Spice isn't as hard to work as I thought it would be.
Thanks for helping by not helping/doing my work

#### kinarfi

##### Well-Known Member
Ok, spice is fun and very helpful, but how do I pick an op amp that represents LM324, TLC27M9CN, amplifier, comparator or a FET that represents IRF3025? Is there a table, is it in the down loadable library?
Thanks,
Kinarfi

#### kinarfi

##### Well-Known Member
Can someone please help with Spice, I'm trying simulate a 110 amp N channel mos FET IRF3205, but I don't know what to do with length, width, areas, or perimeters, or if I want NMOS or NMOS4.
Kinarfi

#### MrAl

##### Well-Known Member
Hi,

Did you go to the IRF site too look for a model first?
That's the first place to look, so you dont have to create one yourself.

#### kinarfi

##### Well-Known Member
Don't know where that is, going to look now, if you have an address, please post.

#### kinarfi

##### Well-Known Member
Hi,

Did you go to the IRF site too look for a model first?
That's the first place to look, so you dont have to create one yourself.
Where would I find the IRF site? I looked, google, but didn't find it. Please and Thanks.
Kinarfi

#### MrAl

##### Well-Known Member
Hi again,

Check here:

International Rectifier - The Power Management Leader

Here is one:

Code:
.SUBCKT irf3205 1 2 3
**************************************
*      Model Generated by MODPEX     *
*   Contains Proprietary Information *
*      Which is The Property of      *
*     SYMMETRY OR ITS LICENSORS      *
*Commercial Use or Resale Restricted *
*   by Symmetry License Agreement    *
**************************************
* Model generated on Apr 25, 01
* MODEL FORMAT: SPICE3
* Symmetry POWER MOS Model (Version 1.0)
* External Node Designations
* Node 1 -> Drain
* Node 2 -> Gate
* Node 3 -> Source
M1 9 7 8 8 MM L=100u W=100u
.MODEL MM NMOS LEVEL=1 IS=1e-32
+VTO=3.73234 LAMBDA=0 KP=95.6501
+CGSO=3.64213e-05 CGDO=3.70824e-07
RS 8 3 0.00550387
D1 3 1 MD
.MODEL MD D IS=3.83979e-08 RS=0.00445428 N=1.48671 BV=55
+IBV=0.00025 EG=1 XTI=2.99617 TT=0.0001
+CJO=3.67939e-09 VJ=1.02405 M=0.469188 FC=0.5
RDS 3 1 2.2e+06
RD 9 1 0.0001
RG 2 7 3.97088
D2 4 5 MD1
* Default values used in MD1:
*   RS=0 EG=1.11 XTI=3.0 TT=0
*   BV=infinite IBV=1mA
.MODEL MD1 D IS=1e-32 N=50
+CJO=4.94117e-09 VJ=0.598326 M=0.650772 FC=1e-08
D3 0 5 MD2
* Default values used in MD2:
*   EG=1.11 XTI=3.0 TT=0 CJO=0
*   BV=infinite IBV=1mA
.MODEL MD2 D IS=1e-10 N=0.433451 RS=3e-06
RL 5 10 1
FI2 7 9 VFI2 -1
VFI2 4 0 0
EV16 10 0 9 7 1
CAP 11 10 4.94117e-09
FI1 7 9 VFI1 -1
VFI1 11 6 0
RCAP 6 10 1
D4 0 6 MD3
* Default values used in MD3:
*   EG=1.11 XTI=3.0 TT=0 CJO=0
*   RS=0 BV=infinite IBV=1mA
.MODEL MD3 D IS=1e-10 N=0.433451
.ENDS irf3205

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#### kinarfi

##### Well-Known Member
Thanks MrAl, I'll try to enter this, but may have to ask How
After plugging in the first diagram, I moved on to this and it works,
Good tool, this spice!
Thanks again,
Kinarfi

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#### MikeMl

##### Well-Known Member
Here is a running LTSpice sim incorporating the IRF3205 model posted above. I included a zip file, which should run if you unpack it into a new directory.

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#### kinarfi

##### Well-Known Member
Thanks Mike, sorry for the slow come back, had guests and was downstairs trying to make my new circuit work and play with mechanical toys, thanks for suggesting spice. Learning, but it helped me simplify the circuit after you suggested that there were other ways to accomplish what I was trying to do, got rid of a bunch of pots. Take a look at the new design, a lot simpler than before, but if you can tell me, why won't my scr shut off when the drive to FETS 2 & 3 are shut down?
Thanks,
Jeff

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#### kinarfi

##### Well-Known Member
I need some help, Please. Originally, as the relay started to activate, the voltage that activated C4 would go to 0 and C4 never gets closed and couldn't seal itself in, So I put an SCR in the circuit to hold power for C4 to close and seal itself in via FETs 2 or 3. When FETs 2 or 3 turn off, the SCR should turn off also, but it doesn't.
I always called this a relay race, and the important one is losing the race.
In this circuit, the pulsed 9.8 volts come from an op-amp that is triggered by a voltage rise on a .1 ohm resistor, the SCR fires but, still won't turn off when FETs 2 or 3 turn off.
Anyone have any ideas or alternate ways to defeat the relay race?
The gate voltage on the SCR should be a 0 because the diode is dropping the voltage offset of the op-amp.

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#### kinarfi

##### Well-Known Member
I've also learned not the ask thing like how do you make a 'model' for an SCR in spice, so I am asking where do I go to learn how to. I have the .sub file. and I found out you can only have one include in a design. Again, where are the instructions, manual, how to's for Spice,
In other words, you don't have to give a fish to eat, or even teach me how to fish, just tell me where to go to learn, please and
Thanks
Kinarfi

#### ericgibbs

##### Well-Known Member
I've also learned not the ask thing like how do you make a 'model' for an SCR in spice, so I am asking where do I go to learn how to. I have the .sub file. and I found out you can only have one include in a design. Again, where are the instructions, manual, how to's for Spice,
In other words, you don't have to give a fish to eat, or even teach me how to fish, just tell me where to go to learn, please and
Thanks
Kinarfi
hi,
Have you signed up for the LTspice Yahoo group.?

As you say, when a man keeps asking for a drink of water, its easier to show him where the well is.

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#### MrAl

##### Well-Known Member
Hi there,

First off, that diode on the FET gate is either drawn wrong or is not connected
properly. It should be reversed. It may already be that way in the circuit if
the FET is really turning on, or maybe the FET is shorted anode to cathode
so it looks like it is turning on but it isnt, it's always on.

Can you draw a diagram to show exactly what contacts close when C4 is energized?
It's a little difficult to tell from that drawing. Show contacts as shorted with
a red line or something when the coil is not energized, then with a blue line
which contacts are closed when the coil is energized.

What is this device supposed to do?

#### kinarfi

##### Well-Known Member
Thanks, and no, have not joined but will, and yep, I get a lot more water that way, hopeful, I can even take a bath, and in private, too.
MrAl, the diode was drawn backwards, The SCR turns on like it should, but won't turn off

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#### kinarfi

##### Well-Known Member
Steering controller

I've posted this earlier, but, what I'm doing is controlling a motor via a stain gauge and the relay is to remove the signal to the FET that is controlling another relay that is connecting the motor to a PWM signal and + power. When the motor reaches the end of it's travel, the motor stalls and current rises and the voltage across the .1 ohm goes up and is compared to a set voltage and fire the SCR which stays fired to pull the relay in. The normally closed and open contact are indicated by the drawing in the middle of the relay.

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