KiCad/ngspice 555 timer simulation


I read much material on 555 timer simulation in the last few weeks, so maybe my memory is playing tricks on me:

I think someone on this forum wrote that he’d simulated a 555 timer circuit with KiCad/ngspice. Unfortunately I did not bookmark the thread at the time and now I can’t find it using the forum search.

If you’ve done some 555 timer simulation with ngspice, could you please raise your hand?


I have not tried to access ngspice from KiCAD, but providing a little more information may help you get useful responses.

Are you having difficulties getting ngspice to run when called from within KiCAD? Any model for a 555 timer must be produced as a SPICE “subcircuit”. I recall some recent posts about passing information for SPICE subcircuits from KiCAD to ngspice. Search for threads with the keyword “subckt”.

Is your problem more related to modeling the 555 timer, or simulation in general? Even though the 555 has been around since before I could (legally) buy a drink, it is a somewhat complex IC. Some models have problems with simulation convergence (you may get a “Timestep too small” error) while others are so simplified that they reveal none of the details you typically use simulation to investigate. If your problem falls into this category, try a different model. I believe there are several posted in the LTSpice User’s Group on Yahoo.



Hopefully you get this sorted. @mifi is keeping a hints page for this kind of thing so report back and let him know how you solved this so he can add it.


I haven’t even begun simulating the 555 with Kicad/ngspice. ATM, I have a simulation running in Multisim but I am eager to reproduce the schematic in KiCad and simulate it there. It’s just that I read so much stuff on internet forums in the last few days (including the stuff @mifi posted) that I was not shure if my memory is playing tricks or if my search-foo for this forum is depleted.

Thanks for the responses, I’ll resurrect this thread when/if I have simulation results.


There are some simulation results for the 555 timer on the ngspice discussion forums (not yet involving KiCad) at Some tweaking of the PSPICE compatible library TCL555.lib from TI was necessary.

I am working on a solution that ngspice does this translation automatically, that is it is reading PSPICE compatible device libs. Please see Your comments on this are welcome!