Simulation of Howland current source issues

[Petar94]

Hello! I’m new to Kicad and I’m tring to learn it and in the same time do some simulation tests for school.
I can’t seem to find the reason why I can’t run the simulation of the basic schematic for “Howland current sourse”.

I get this as a feedback for the simulation:
"warning, can’t find model nc_01
Circuit: KiCad schematic
Error on line 5 :
zl 0 vout 10k
**Unable to find definition of model **
Note: can’t find init file.

---

**** ngspice-32 shared library**
**** Creation Date: Fri Jul 10 12:37:34 UTC 2020**

---

Error: there aren’t any circuits loaded."

I would be really gratefull if someone would be able to help me and share some videos or other sources for guides to work with Kicad.

[ML9104]

First, a good idea would be to connect a power supply to your opamp. Simulators like that. In fact, they don’t work without power.
Here’s a way to do it:

Power supply for Simulation (and ERC)

For schematics that are for simulation (as well as passing ERC) and have no own power supply section, I’ve found this little thing useful. Just place it on your schematic sheet, and you have power for your circuit. The voltage sources are from the “Simulation_SPICE” library and can be edited for other voltages. The other symbols are from the “Power” icon on the right side of the screen. You get the idea, nothing revolutionary, but perhaps useful for a beginner. Cheers. [power]

[holger]

Please have a look at KiCad Eeschema as GUI for ngspice, tutorial for setting up the simulation

You need to attach a spice model to the opamp symbol.
The opamp needs positive and negative supply voltages.
The load resistor should ber called RL1, as all resistors have to start with letter R.

You should update KiCad, as ngspice-32 is very old. ngspice-41 is the current version, available with KiCad 7.0.9. If you are interested mostly in simulation, you should even use the nightly 7.99, as the interface to ngspice has been improved a lot, and it has a general spice model for the opamp in its Simulation_Spice library. However, schematics and pcb then cannot be read with version 7.0.x or older any more.

[Petar94]

Thanks for tips. I will try to implement the schematic according to your tip and I will upload the result.

[Petar94]

So I did the updates based on your tips. But I still can’t get it working, probably I’m missing something. Can you check the new circuit and give me some suggestions.

Also here is the feedback when I try to start the simulation:
warning, can’t find model vcc+
Circuit: KiCad schematic
Error on line 3 :
u1 net-r3-pad1 net-r1-pad1 net-r2-pad1 vcc+ vcc- opamp
Unable to find definition of model vcc+
Error: circuit not parsed.
Error: vector time not found!
Error: vector time not found!

[ML9104]

You’re missing the PWR_FLAG part.
But this is mainly relevant for ERC.
You seem to be using a very old Spice library. I can only second Holger: update to 7.0.x