App note from Precision Microdrives helping you model DC motors in SPICE. Link here
SPICE (Simulation Program with Integrated Circuit Emphasis) is an open-source program for simulating electrical circuits. It enables engineers to model the behaviour of their circuits in software, which reduces prototyping costs and time.
As DC motors have mechanical properties – i.e. they cannot be simulated accurately only considering electrical properties – it can be difficult to use them in SPICE. This Application Bulletin guides you through the principle of operation and extends the DC motor model for vibration motors and gear motors.