AVR-Chat

Seems kinda obvious now, but I wasn't getting there on my own  [:">]

Thanks for taking the trouble to write. Will give it a go.

Cheers

Bernie





--- In AVR-Chat@yahoogroups.com, David VanHorn  wrote:
>
> Now from a real keyboard:
>
> As long as the motor hasn't moved, then re-energizing with the same
states,
> and accelerating from there will work.  If the motor could move, then
you
> will need some sort of position information from an encoder or some
such.
>
> If you are using the port to keep your output states, that's part of
your
> problem.
> Use a ram variable, and copy that out to the port when you change
states.
> Then when you power down, the ram variable knows where you were, just
> output that to the port again, and carry on from there.  Make sense?
>
>
>
> On Sun, Apr 28, 2013 at 12:24 PM, David VanHorn microbrix@... wrote:
>
> > You need to.keep a var with the old output state just before you
turned
> > them off. Then restore that before moving.
> > On Apr 28, 2013 10:50 AM, "Bernie" berniemcintosh@... wrote:
> >
> >> Hi,
> >>
> >> I have implemented a project using an ATMega328 to drive a stepper
motor.
> >> Once the motor has reached the position required, I don't need it
to move
> >> any more for say, 10 minutes at a time.
> >>
> >> The motor is taking current 100% of the time of course.
> >>
> >> I'd like to turn the power to the motor off, then the next time I
need to
> >> move the load, start it up again without having lost the position
> >> information.  Holding torque is not a concern.
> >>
> >> I've tried this using the simple means of bringing the four outputs
from
> >> the AVR low. When it comes to step the motor again, the first few
pulses do
> >> not have any effect on the motor, so I lose steps and now don't
know where
> >> the motor is - necessitating a reset cycle to bring it back to a
limit
> >> switch.
> >>
> >> On making that first step after its been switch off, I've tried
every
> >> possible beginning step sequence but can't get the right result.
> >>
> >> I'm coming to the conslusion that it can't be done. If you want to
keep
> >> position intact, then don't turn off the outputs. If you do turn
off the
> >> outputs you have to find its position again by sending it off to
the limit
> >> switch.
> >>
> >> There may be other approaches by using more sophisticated hardware
but at
> >> the moment the question relates to using this simple means of
control as it
> >> has the lowest component costs.
> >>
> >> I'd be grateful if anyone here could comment. Apologies if its more
a
> >> stepper question than an AVR question but I'm thinking that its
relevant to
> >> many AVR users.
> >>
> >> Regards
> >>
> >> Bernie McIntosh
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> ------------------------------------
> >>
> >> Yahoo! Groups Links
> >>
> >>
> >>
> >>
>
>
> [Non-text portions of this message have been removed]
>



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