The Polulu H-bridge is in fact a "class D amplifier." Exactly the same thing. You put a logic level signal in the PWM input and a powerful high current signal comes out the other side. It's a class D amp. OK, it is a rather specialized Class D amp. It only accepts square wave inputs but, no difference.
On Thu, Oct 15, 2020 at 3:23 PM Gene Heskett <ghesk...@shentel.net> 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... > > > 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 > > 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 > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
