AVR-Chat

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

katraven1 wrote:
> wow.. thx for the readings =)
> 
> after that I've done some more research into this area and some more 
> n00bie questions arose:
> - jst want to confirm: it is possible to directly connect the mega32 
> to the L6203s to drive the motors right? *looks nervous.. what we 
> have atm is the bidirectional DC motor control circuit suggested in 
> the datasheet for the L6203, replacing the L6506 with the mega32..
> 
> - how does one know if the motor can be driven using lock-antiphase 
> or not? there doesn't seem to be anything mentioned in the 
> datasheets...
> 
> thx guys for your help
> 
> --- In AVR-Chat@yahoogroups.com, "Larry Barello" <yahoo@...> wrote:
> 
>>Check out www.barello.net/Papers/Motion_Control
>>
>>I find that using the ENABLE input gives less control over the 
> 
> motors.
> 
>>After you have puzzled through the paper, above, then look at
>>
>>www.barello.net/Papers/H-bridge.pdf
>>
>>The hand drawn graphs in that paper were taken directly from an 
> 
> oscilloscope
> 
>>screen.
>>
>>
>>Cheers!
>>
>>
>>-----------
>>Larry Barello
>>www.barello.net
>>
>>
>>| -----Original Message-----
>>| From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] 
> 
> On Behalf
> 
>>| Of katraven1
>>| Sent: Saturday, August 26, 2006 11:07 PM
>>| To: AVR-Chat@yahoogroups.com
>>| Subject: [QUARANTINE] [AVR-Chat] Re: PWM for reversible DC motors
>>| Importance: Low
>>| 
>>| thx for that help =)
>>| 
>>| *feeling very n00b...
>>| 
>>| jst wanna confirm:
>>| we're using an L6203 for each H-bridge, which has 1 enable and 2
>>| inputs. Am i right to say that the two inputs change the 
> 
> direction
> 
>>| of the motor?
>>| as in, if i put the PWM into input1, it'll go one way and vice 
> 
> versa
> 
>>| if i put it into input2? I can't seem to find a good ref which 
> 
> has
> 
>>| this explained clearly...
>>| 
>>| and, if this is the case.. how could I configure the other ports 
> 
> to
> 
>>| change the direction?
>>| 
>>| --- In AVR-Chat@yahoogroups.com, dlc <dlc@> wrote:
>>| >
>>| > The Mega32 has two PWM channels (OC's) that you should use for
>>| motor
>>| > speed.  Use one or two of the other IO lines per H-bridge to
>>| select the
>>| > direction.
>>| >
>>| > DLC
>>| >
>>| > katraven1 wrote:
>>| > > we have an ATmega32 connected to 2 H-bridge circuits for 2 DC
>>| motors
>>| > > which need to be reversible..
>>| > >
>>| > > we're using timer1 to generate our pwm signal and my idea 
> 
> was to
> 
>>| use
>>| > > one or the other of the OC1 pins to change direction.
>>| > >
>>| > > would there be a better method of doing this? using my 
> 
> current
> 
>>| > > thinking, the wheels would only be able to work in pairs but 
> 
> not
> 
>>| > > independently...
>>| > >
>>| > >
>>| > >
>>| > >
>>| > >
>>| > >
>>| > >
>>| > >
>>| > >
>>| > > Yahoo! Groups Links
>>| > >
>>| > >
>>| > >
>>| > >
>>| > >
>>| > >
>>| > >
>>| >
>>| > --
>>| > -------------------------------------------------
>>| > Dennis Clark          TTT Enterprises
>>| > www.techtoystoday.com
>>| > -------------------------------------------------
>>| >
>>| 
>>| 
>>| 
>>| 
>>| 
>>| 
>>| 
>>| 
>>| Yahoo! Groups Links
>>| 
>>| 
>>| 
>>| 
>>|
>>
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>  
> Yahoo! Groups Links
> 
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>  
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> 

-- 
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Dennis Clark    TTT Enterprises
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