# EAGLE - Singular matrix warning in RL circuit simulation

I'm studying for my electrical circuits exam and since Eagle is used for some future exams I thought I could learn it and double-check my calculations by simulating with Eagle.

I'm trying to simulate the following circuit, but Eagle is giving me a "singular matrix warning" and failing to simulate. It's also telling me to "check nodes l_l2#branch and l_l2#branch" but I don't know how which nodes those are, or how to get nodes' names.

I searched for this error and what I found concerned voltage sources in a loop (only one source here) or infinite impedance branches (there shouldn't be any). Why isn't the simulation running? Thanks in advance!

Netlist:

* SpiceNetList
*
* Exported from Main.sch at 5/12/19 12:37 PM
*
* EAGLE Version 9.4.0 Copyright (c) 1988-2019 Autodesk, Inc.
*
.TEMP=25.0

* --------- .OPTIONS ---------
.OPTIONS ABSTOL=1e-12 GMIN=1e-12 PIVREL=1e-3 ITL1=100 ITL2=50 PIVTOL=1e-13 RELTOL=1e-3 VNTOL=1e-6 CHGTOL=1e-15 ITL4=10 METHOD=TRAP SRCSTEPS=0 TRTOL=7 NODE

* --------- .PARAMS ---------

* --------- devices ---------
V_V1 N_1 0 DC 1V AC 1V
R_R2 0 N_1 4
L_L1 0 N_3 20m
L_L2 0 N_1 20m
R_R1 N_3 N_1 2

* --------- simulation ---------
.control
set filetype=ascii
OP
write Main.sch.sim
.endc

.END


Schematic:

P.S. Are there any good Eagle tutorials out there focused on SPICE simulation? Moreover, Eagle only allows simulating DC/AC sweeps, transients or at operating point. How do I simulate a constant-frequency AC source?

• the inductor is shorting the voltage source. Commented May 12, 2019 at 10:52
• Which inductor, and how would I go about fixing this? I don't see any short-circuit in the schematic and I copied it verbatim from the professor's handout...
– kmf
Commented May 12, 2019 at 10:56
• If you cannot see that L2 is across your voltage source, perhaps this is a good time to practice redrawing the circuit to get familiar with seeing parallel and series connections. Commented May 12, 2019 at 11:36
• Add a tiny resistance in series with L2.
– Chu
Commented May 12, 2019 at 12:32
• Got it, thank you. So this is a shortcoming of ngspice's capabilities, it can't simulate ideal circuits? (makes sense) How would I go about solving it? Adding a small resistor in series? EDIT: @Chu, didn't see your comment. I'll try, thank you!
– kmf
Commented May 12, 2019 at 12:38