Forums » General Electronics Discussion

I'm new to designing circuits. I have a basic understanding of an electronic circuit. I would like to design the circuit using software but I'm not sure what to call the motor on the CircuitLab site and how to set up the rest of it.

The simplest way to model a DC motor is to just use a resistor of a value given by Vsupply/Imotor:

where Vsupply is the rated nominal voltage across the motor and Imotor is the rated current drain of the motor at Vsupply.

This thread might help in finding out about DC motor modelling in CL.

https://www.circuitlab.com/forums/modeling-and-simulation/topic/g4w7t2s9/pmdc-motor-does-anyone-have-a-model/

Search CL for:

dc motor

for some more ideas and circuits for motor controllers.

Usually PC fans have brushless motors which can’t be directly compared to ordinary DC motors. They have internal electronics that needs supply voltage (2 wire fan), or supply + PWM input for speed control (3 wire fan), or supply + PWM input + rpm output (2 pulses per turn) (4 wire fan).

The 2 wire fan can (somewhat) be controlled by voltage, but this is a very bad solution, not reliable, and you need full voltage (min 1”) to kick start the fan. Not recommended!!!

Take care with supply and control signal voltage, could be 12V, 5V, 3.3V ...

Due to bearing problems all PC fans should be kick started to full speed for some seconds. For an example see:

Regards, Sancho

@Sancho_P,

Good point. I'd forgotten that PC fans are brushless.

:)