Discussion Forum

Hi

in the CIR BC node list (right click) you have the three last entries to link a CIR to another physics:

"External I Vs. U 1" node connects an arbitrary voltage measurement (exit current versus Voltage measured)
"External U Vs. I 1" node connects an arbitrary current measurement
"External I-Terminal 1" node connects an arbitrary voltage-to-ground measurement

When you have defined a ground and at least one terminal you can connect it via these I/F

Another information: Do not leave a Terminal node,coupled to a circuit, even if "disabled", because it is not fully "disabled" COMSOL 4.1 fails to solve such a model, just reset the Terminal to "voltage" or "current" and disable or override it and it's OK, or delete the node if it is not used any longer.

Another caveat, if you have tested and solved your model without CIR physics, then add the CIR physics, be prepared to add a new study, or delete the current solver sequence and regenerate a new one

Here is a simple example CIR + JH in v4.1.0.185 (I do not have 3.5 any longer, sorry)


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Good luck
Ivar

Dear All,

I carefully searched the forum an followed the advises, but still have a problem "failed to find a solution, the last step did not converge"
I am trying to model a piezo transducer excited by a voltage ramp function. I use time -dependent analysis, piezoelectric device and electric circuit physics. I added a terminal in piezo physics, and an external current terminal in the circuit physics. Assigned them both node # 1. Connected a capacitor between nodes 1 and 2, a resistor between 1 and 0, and a voltage source between nodes 2 and 0. I use sine voltage, because I do not know how to assign a ramp or a piecewise function for the voltage source. Even with the sine voltage, comsol gives an error "nonlinear solver did not converge", "last time step did not converge". Can anyone please help me with two things:
1) to assign a ramp or a piecewise function for the voltage source, for the circuit, not for the surface of the piezoelectric, because that one I am trying to calculate, and
2) to model it properly, so that the solution converges.
I attached the model.
Thank you very much in advance.
Victor Klymko

Dear Victor ,

Thank you for your question and putting you model made the problem easier.

I just have a look on your model and I think your problem is coming from your " Electrical Circuit " .

Normally now is working . Try to take a look and let me know if it's ok.

Thank you very much Omar!
It works, the only thing is I wanted the resistor to be in parallel, and the capacitor in series with the transducer, as shown on the attached sketch.
One thing I did not understand in your model is that in the "electric circuit" physics, the external current terminal is assigned to node 3, while in the "piezo devices" physics, the surface of the piezo is the terminal 1. Shouldn't it be the same node? From reading the docs, I understood that external terminal is the way to connect a piezo surface, but it does not work when I connect the external I terminal to piezoelectric terminal.
Any way, I am getting something close to the previously published results.
Thank you very much.
Victor

Hi Victor ,

You can also set an electrical circuit like in the PDF, you could modify my model and instead of the resistor you can put the capacitor and then you obtain exactly the circuit described on the sketch. ( I hope the model will be consistent ).

I hope it's gonna help you.

Omar.

"The External I-Terminal node is used to feed a user defined voltage-to-ground into a single node in the circuit. The resulting circuit current must be connected to the external device (finite element model) unless coupled via a circuit terminal."

Dear Victor,
Do you still have this model and upgrade it to the newer version of Comsol? I am facing the same problem but cannot used the posted file.
Thank you very much indeed.
Best regards,
Tung