AVR-Chat

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@gmail.com> 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@yahoo.es> 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
>>
>>
>>
>>
>>
>>
>>
>>
>> ------------------------------------
>>
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>>
>>
>>


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