On Thursday 15 October 2020 19:06:30 Gene Heskett wrote: > On Thursday 15 October 2020 18:20:08 Gene Heskett wrote: > > On Thursday 15 October 2020 17:17:59 Thaddeus Waldner wrote: > > > The reactance and inductance questions are above my pay grade and > > > I’d be happy to hear someone explain it. :) I use these for > > > robotics class in place of the old BJT L298, which are > > > optimistically rated for 2 amps but have more than 2v drop at much > > > less than that current. > > > > > > Maybe I don’t understand your comment but I’m pretty sure that a > > > 50% duty cycle PWM waveform will run the motor at half-voltage. > > > > What I had in mind was a quicker than hal's logic can do it, as hals > > direction reversal by controlling the inA and inB inputs will be > > plenty slow enough to have it oscillate possibly uncontrollably. > > This may not be the ideal device, we'll have to see once they > > arrive, which could be as early as Monday. > > > > What I have in mind is basically a 400 watt or more, class D audio > > amplifier. Maybe I've gone looking using the wrong search terms. > > Yes and with very similar pricing, a dual 2kw is $25. I'm > > thinking... > > So I've bought one of these too, and will see if I can somehow bypass > the input coupling caps and make it run down to to DC. Or better yet, > scaled to a 5 volt dc coupled pwm. And I neglected to include the link: <https://www.ebay.com/vod/FetchOrderDetails?ViewPaymentStatus&purchaseOrderId=260000589842041> > > > You command the direction with INa and INb according to the Truth > > > Table. The PWM signal will then switch either the A or B low-side > > > FETs, depending on the INa/INb configuration. > > > > > > > It would appear that when enabled, and lets say with a pwm > > > > frequency near the top of the 10khz range, that a 50% duty cycle > > > > pwm waveform would be the equ of a balanced, at rest servo, so > > > > my first question is how much additional inductance in series > > > > with the motors leakage reactance will be needed to protect the > > > > chip from the current surges at the pwm waveforms transition > > > > points? > > > > > > > > My hal file will obviously need to stage an initial enable at > > > > the 50% duty points, then let the pid output thru. > > > > > > _______________________________________________ > > > Emc-users mailing list > > > [email protected] > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > Cheers, Gene Heskett > > Cheers, Gene Heskett
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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
