Just read the data sheets. at 50% PWM the mother turns with about 1/2 speed. The current will be about 1/2 what it would be at 100% Try it.
If you don't want to build an experiment then open up a battery powered power tool and take some measurements with a scope. I'd bet 50% PWM places the motor at close to 50% RPM, with no load. You can apply a brake but not a hold to a brushed DC motor by shorting the power leads or with a larger motor shorting through a power resister but this does not work predictably and will not hold a position. Try it. Shorting the leads makes the shaft hard to turn. But there is not a lot of practical use for this A more reliable way to hold a position with a DC brushed motor is to use quadrature encoder feedback. The PID control will do "whatever" to hold position using as much torque as needed, up to some limit. Holding position does require and active controller. On Sun, Oct 18, 2020 at 11:36 AM Thaddeus Waldner <thadw...@gmail.com> wrote: > Correct me if I’m wrong; the only motors that lock the rotor by applying > current are steppers. All other motors produce torque when current is > applied. > > With a sufficiently high PWM frequency, you can apply a 50% PWM voltage as > you describe, but due to the induction, there will be near-zero current, > and near-zero torque. The motor will free-wheel. > > > On Oct 18, 2020, at 12:07 PM, John Dammeyer <jo...@autoartisans.com> > wrote: > > > > t's still a 20kHz PWM which is a period of 50uS. So CW for 2.5uS, OFF > for 22.5uS, CCW for 2.5uS, OFF for 22.5uS. The current limiting feature > still comes into effect if the current increases past the example 3A but > the overall average current for the entire 50uS period has dropped to 10%. > Now the motor doesn't heat up as much but is still locked. > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
