On Sunday 18 October 2020 06:05:44 Nicklas SB Karlsson wrote: > The theory is that if the PWM signal is high the H-Bridge is switched > to > > >> say turn the motor clockwise. If the PWM signal is low > >> > >>>> the H-Bridge is switch to turn the motor counter clockwise. > >>>> Therefore > >> > >> with 50% the motor is first asked to turn one way and then > >> > >>>> the other. That results in the motor essentially being locked in > >>>> place. > > > > The above is not the way it works. No one would design anything > > like that. But let's say you did. What would happen? The motor > > would vibrate and slowly rotate and have close to zero torque
But, if it did drift, because that vibrational ripple essentially cancels any friction in the system and if it is fitted with a quadrature encoder, which mine is, the encoder would soon issue enough error to drive it back to balance. One however, might have to set a deadband of more than one count to keep it from oscillating. For this seat motor controller the T-del max of 1800 u-secs when switching directions bothers me. T-del typical is 600 u-secs. Computer control is NOT hand switches and can be much faster than that. But we'll see when it gets here. But, having now discovered how to make use of unconfigured functions in the 7i76D, there are at least 4 functions that will get rewired yet today as they need only 5 volt controls. If I don't wear me out first. :( > It does work with high enough switching frequency because motor > inductance average out applied voltage to a more or less triangular > current over one switching period. With high enough switching > frequency current ripple is low enough average is more or less equal > to analog voltage and current. > > ... > > Nicklas Karlsson > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
