This is from a thread that was closed and I would like to participate in the solution!
So as the other thread was closed, I'm starting a new one to try to solve it, because I'm also having troubles to find some values.

So I setup the circuit in LTSpice


Then I used some nodes and that net A to write some equations.
I can only match the current flowing through R with LTSpice value but not the other currents.

Here is my work


In the end are the two other currents that doesn't match LTSpice values!

 

Check yor math I = - 79.6667A

Therefore

I3 = 20A - (- 79.6667A ) - 180A = -80.3333A

I2 = 20A - (- 79.6667A ) = 99.6667 A

 

First thing is that your circuit does not match the original circuit in the other thread. In your circuit, I4 is a current source that appears to be set to a constant value of 180 A. In the original circuit, it is a current-controlled voltage source in which the controlling current is the current flowing right to left in R3 and in which the scaling coefficient is 9 V/A.

So if your work (which I haven't look at yet) is based on the original circuit, then it won't match the simulation.

The simulation results shown match the circuit as you've set it up (not surprisingly).

One thing to keep in mind with sim results is that the current is a component is the current flowing into whichever pin is pin 1 on the symbol. The schematic doesn't indicate which pin is pin 1. That's why the first thing I did with my install of LTSpice was to modify the basic library symbols to place a small, unobtrusive tick mark on the side of the R, L, and C symbols to indicate pin 1.

 

Check yor math I = - 79.6667A

Therefore

I3 = 20A - (- 79.6667A ) - 180A = -80.3333A

I2 = 20A - (- 79.6667A ) = 99.6667 A

Hum, ok but LTSpice also says it's a positive value! Why there is this difference in signs? Is it because of the component's orientation in the circuit?

First thing is that your circuit does not match the original circuit in the other thread. In your circuit, I4 is a current source that appears to be set to a constant value of 180 A. In the original circuit, it is a current-controlled voltage source in which the controlling current is the current flowing right to left in R3 and in which the scaling coefficient is 9 V/A.

So if your work (which I haven't look at yet) is based on the original circuit, then it won't match the simulation.

The simulation results shown match the circuit as you've set it up (not surprisingly).

One thing to keep in mind with sim results is that the current is a component is the current flowing into whichever pin is pin 1 on the symbol. The schematic doesn't indicate which pin is pin 1. That's why the first thing I did with my install of LTSpice was to modify the basic library symbols to place a small, unobtrusive tick mark on the side of the R, L, and C symbols to indicate pin 1.

Ok, so how would a dependant current source would be setup in LTSpice for this circuit?

 

I tried to replace that current source with a dependant current source but I'm getting an error while trying to simulate!


If someone can help me setting it up correctly, I'll check the differences!

Thanks

 

I don't have LTSpice on a machine that's handy and I haven't played with dependent sources in it before. But from the schematic it looks like you have a controlling current called I1 but the currents in the schematic (the blue text) are I, I2 and I3. So where is I1 defined?

 

I don't have LTSpice on a machine that's handy and I haven't played with dependent sources in it before. But from the schematic it looks like you have a controlling current called I1 but the currents in the schematic (the blue text) are I, I2 and I3. So where is I1 defined?

Ah ok. I1 is that current being supplied by I1 current symbol in the schematic!

 

Ah ok. I1 is that current being supplied by I1 current symbol in the schematic!

Okay. But that's NOT the current that the original schematic has controlling the dependent source.

Are you trying to set up the same circuit that was in the original thread? Or are you trying to do something else?

 

If you do a Google search on "LTSpice current-dependent voltage source" you will get lots of hits.

I picked the first one on the list that I saw and it seems to tell you exactly how to do it.

 

I watched that video but I thought that in the circuit we are discussing, it was a current controlled current source. That video is a voltage controlled current source. I got confused by the names!

In the meantime I changed the circuit:


Would this be it?

 

Okay. But that's NOT the current that the original schematic has controlling the dependent source.

Are you trying to set up the same circuit that was in the original thread? Or are you trying to do something else?

Yes, I was trying to setup the same circuit!

 

Yes, I was trying to setup the same circuit!

So I would recommend following the steps in that video. I think you could shortcut it by using the current in the resistor directly, but that leaves it ambiguous as to the direction of the current since there's visible indication of which pin is pin 1.

 

So I would recommend following the steps in that video. I think you could shortcut it by using the current in the resistor directly, but that leaves it ambiguous as to the direction of the current since there's visible indication of which pin is pin 1.

I followed the video in my post #10. It's still incorrect? Apparently, that voltage controlled current source needs a voltage symbol name so that it can work properly. So I added a Voltage source where current 'i' flows and gave it a value of 0V as they do it in the video.

 

I followed the video in my post #10. It's still incorrect? Apparently, that voltage controlled current source needs a voltage symbol name so that it can work properly. So I added a Voltage source where current 'i' flows and gave it a value of 0V as they do it in the video.

You want a current-controlled voltage source (and H device, if I recall).

I'm not sure which pin is pin 1 on a voltage source. A couple tests would make it obvious. In the meantime, try either turning the V3 source around or making the gain on the dependent source -9 (V/A).

 

Good morning!

Ok, I edited the symbol (I'm now at work and LTSpice color scheme is different) for the current-controlled voltage source (H symbol) and where you see the '+' sign is where is pin 1.

I used -9 for the gain!
Here are the results!

 

Good morning!

Ok, I edited the symbol (I'm now at work and LTSpice color scheme is different) for the current-controlled voltage source (H symbol) and where you see the '+' sign is where is pin 1.

I used -9 for the gain!
Here are the results!
View attachment 144976

Hi there,

Is that controlled source with the "-9" really supposed to be minus 9 and not plus 9?
Anyway, for the original circuit in the other thread i got all negative values for the node voltages.

If you want to solve this yourself you should really show your set of equations so we can take a look.

Also, if you have too much trouble, replace H1 with a CONSTANT voltage source and see if you can solve it like that first. If you can solve it like that, then you can solve it with a controlled source too with just a little more work. Because these circuits are linear there are a lot of tricks that come into play that we dont usually see published, but the main idea is to get the circuit solution with a constant source first just to make sure you know how do to it that way. If you show your equations, we can go over them.

 

Good morning!

Ok, I edited the symbol (I'm now at work and LTSpice color scheme is different) for the current-controlled voltage source (H symbol) and where you see the '+' sign is where is pin 1.

I used -9 for the gain!
Here are the results!
View attachment 144976

If the + sign is pin 1, then I would expect the controlling current to be the current INTO pin 1, which is the direction defined for the controlling current in the original schematic. So, with that orientation of the sensing voltage source, you would want a gain of +9.

 

Hi there,

Is that controlled source with the "-9" really supposed to be minus 9 and not plus 9?
Anyway, for the original circuit in the other thread i got all negative values for the node voltages.

If you want to solve this yourself you should really show your set of equations so we can take a look.

Also, if you have too much trouble, replace H1 with a CONSTANT voltage source and see if you can solve it like that first. If you can solve it like that, then you can solve it with a controlled source too with just a little more work. Because these circuits are linear there are a lot of tricks that come into play that we dont usually see published, but the main idea is to get the circuit solution with a constant source first just to make sure you know how do to it that way. If you show your equations, we can go over them.

I already solved the circuit in post #1 and then Johny130 corrected some of the math I was doing wrong! I.e., using a constant current source.

If the + sign is pin 1, then I would expect the controlling current to be the current INTO pin 1, which is the direction defined for the controlling current in the original schematic. So, with that orientation of the sensing voltage source, you would want a gain of +9.

Ok, so let me change that to '+9' and I'll post the results in a bit!

 

I think this is the same as I posted in post #10.



Anyway, if this is the correct circuit to simulate the other one from the other thread, I would now like to know what is the difference in terms of equations after plugging in this different dependant element!

 

Can you clearly emphasize the problem you have? You do not know how to solve circuits with dependent sources or what?

As a side question. Why do you use transient analysis in LTspice (instead of .op) to solve the DC circuit ?