Stepper motor oscillates in reverse using Arduino

[RavensFan]

Theoretically, there should be no difference.  They are both just numbers.  What numbers are coming in from the analog read?  Put an indicator, or better yet a waveform chart, to see what the analog values look like.

Is it possible that the act of turning on the motor is causing some noisy signal that is intefering with the analog reading and causing it to fluctuate between negative and positive?

[Carlr]

RavensFan,

Thanks for the suggestion. Find attached the signal charts and the vi used to produce them. The signal does flustuate a ltittle, but never enough to go positive and then negative. At start up oand shut down there is no spike in the signal either.

To produce this chart i started with the potentiometer set to give a negative signal, then increased it to positive, held it positive and then changed to a negative value. the second half of the samples was when there was no change of the potentiometer position, thus giving an idea of the level of signal fluctuation.

Does any one have any further ideas?