AVR-Chat

yay~ success! the motors are in motion.

the current set-up is to drive the motors using signed magnitude, with
the pwm into the enable. now i can drive both motors individually  [:D]

now the next step: connecting the IR sensor... [:-?]

more reading www.barello.net <http://www.barello.net>  - those dilberts
are cool!

but yeah, thx for all your help guys~ otherwise those motors prolli
still wouldnt moving =P


--- In AVR-Chat@yahoogroups.com, Dennis Clark <dlc@...> wrote:
>
> That is true about the glitch, I had a tendency to do a "one wire"
> approach and just enable the bridge, that enable will eliminate the
> glitch. When playing with LA I didn't see high currents, I just noted
> that it was the _same_ current no matter what the motor speed was. I
> did like the responsiveness of LA over SM though you do lose some of
the
> resolution, all things kept the same, but you didn't have that low
> magnitude "dead band" on start up either. All things in trade off.
>
> DLC
>
> Larry Barello wrote:
> > Dennis: Solving the glitch problem was the intended use for the
ENABLE line
> > (and coasting). If you are seeing large current draw with LA then
your PWM
> > rate is way too slow. That is the big problem with LA, IMO, is that
pwm
> > rates of 60-120khz are needed with small, low inductance motors.
> >
> > On my paper, www.barello.net/Papers/Motion_Control I relate the
difference
> > between cheap aircraft servo motors (gutted) and high quality
coreless (I
> > think) MAXON printer motors with PWM @ 15khz (TI 754410): The cheap
motors
> > with iron cores had ~15ma peak to peak ripple while the MAXON motors
had
> > 150ma - about 1/2 the stall current!
> >
> > So, it all depends (as usual)...
> >
> > My other presentation (H-Bridge.pdf) has some graphs and pictorial
> > descriptions of what is happening with the current in an H-Bridge
driven
> > motor situation.
> >
> > In my experience, Synchronous-rectification (i.e. driving the motors
> > on-shorted) gives similar responsiveness and linearity as the LA
approach,
> > with the advantage of 1/2 the ripple.
> >
> > If your hardware (or s/w) is very clever, you can alternate the side
of the
> > H-Bridge doing the rectification (shorting) from cycle to cycle to
double
> > the switching frequency seen by the inductance for a given PWM rate
and cut
> > your ripple in half again. That requires a PWM for each side and
adjusting
> > the phase between them to adjust the duty cycle.
> >
> > Cheers!
> >
> > -----------
> > Larry Barello
> > www.barello.net
> >
> >
> > | -----Original Message-----
> > | From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com]
On Behalf
> > | Of Dennis Clark
> > | Sent: Monday, August 28, 2006 11:49 AM
> > | To: AVR-Chat@yahoogroups.com
> > | Subject: Re: [QUARANTINE] [AVR-Chat] Re: PWM for reversible DC
motors
> > |
> > | Any H-bridge (usually) can be drived locked antiphase. My biggest
> > | problem with locked-antiphase is power up glitch. You have to have
the
> > | PWM at the center duty cycle or the motors turn. Which means that
when
> > | you start up and your line is low, your motor takes off full bore
until
> > | the PWM comes on. The other problem I have with locked antiphase
is
> > | that you pull the same current no matter what the motor speed,
this is
> > | wasteful of power on a battery powered system. I have seen that
locked
> > | antiphase is MUCH more responsive to PWM change.
> > |
> > | DLC
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
>
> --
> ---------------------------------------
> Dennis Clark TTT Enterprises
> ---------------------------------------
>




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