AVR-Chat

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