the time in my simulation "freezes"

[Tien_P]

Hi All,

There is a problem with the 3D model used in the attached circuit it looks like the symbol is missing two pins.  You should use the 5 pins virtual motor instead, the model is exactly the same but you have the two additional pins to connect to externally.   You can find this component in the “Misc” group under the “Misc Virtual” family.

For information how to use 3D motor, have a look at the attached pdf file.

[ehudg]

Thank you for your reply.

in the suggested circuit you've sent, the voltage on the transistor, changed between 11v to 12v. i've made some changes and now it changes properly between 0v to 12v (Vcc). in the output of the circuit i'm getting DC voltage changing as well between 0v to Vcc (as it supposed to be).

i've realized that no matter what voltage being "fed" to the motor the rpm is between  "-22.687" to "-22.785", which is a very minor change. as i understand the speed of the DC motor should be directly changed according to the value of the DC voltage on it's inputs. why is it so, and where can i get a motor that actually going to work?

[lacy]

I have seen what you describe about the motor voltage since Version 2001. The documentation says that the motor voltage should be indicitive of the motor's RPM. But I have never seen it work right.

Maybe NI has information that we don't know at this time, but in my opinion the motor model is not working correctly.

Have a Nice Day

[Andrew_Boniface]

The problems here seem to stem from two possible causes: 

1.  Numerical simulation of a switch (FET, for example) causes difficulties because of discontinuities introdused by the on-off transition.

I am working an a method for numerically simulating switch=mode circuits which accomodates these discontinuities.

2.  The model used for the motor is not adequate for this application.

Unless this may be solved by application of the methodology above, I cannot help at this time.

[lacy]

I respectfully disagree with your hypothersis. I know that the motor model does not work as the documentation says it is supposed to work It hasn't functioned correctly since Version 2001. It has nothing to do with the attached circuit. You could put a battery with a varible resistor across it and it would still give the -22 V reading on the meter reguardless of the pot setting. Now as far as suitability for a specific purpose. that would have to be left up to the circuit designer as to whether it meets his purpose.

Have A Nice day

[Andrew_Boniface]

My apologies.  Not knowing the motor model at all, and not having a chance to try it, I assumed it was good for _some_ application. 

By laws of logic, if motor model is not good for any application, then it is not good for yours.  My hypothesis two technically covers this situation, though it's not very helpful in this context.

My primary interest is in simulating the PWM,  and numerical analysis techniques for obtaining the most accurate simulation for the least computational work.  If the motor model is at fault,  improving the numerical simulation (except possibly the simulation of the motor) will not fix things.