[apernell]

If the stepper motor is rated at 1.8 amps per phase should I set the driver current at around 1.8 or double that?

[awerby]

Right; only one phase operates at a time (they alternate in a stepper motor) so you don't have to double it. In fact, you can decrease it, since the motor won't draw that much current, depending on how it's wired. But if you're feeding more than one motor with a single power supply, there has to be enough current available for all of them. Here's how Mariss explains it on the Geckodrive site:

"The easiest factor in choosing a power supply is its current rating, which is based on your motor ratings. A motor control will always draw less than 2/3 of the motor’s rated current when it is parallel (or half-winding) connected and 1/3 of the motor’s rated current when it is series (or full-winding) connected. That is to say, a 6 amp per phase motor will require a 4 amp power supply when wired in parallel and a 2 amp power supply when wired in series. If multiple motors and drives are used, add the current requirements of each to arrive at the total power supply current rating."

http://www.geckodrive.com/app-notes.html

[apernell]

Thanks Andrew ..big help

[UA_Iron]

No, set the driver at the rated value.

"It is recommended the motor current always be set at the rated value also to get the best microstep smoothness. Setting the current higher degrades the linearity of the motor and causes microstep bunching and attendant low-speed vibration. "
-From the gecko drive page cited above.

What is quoted previously is for determining the power supply current, not the driver current/phase setting.

[James Newton]

awerby quoted something about the necessary supply current. UA_Iron is correct, and has quoted the actual setting on the driver.

[awerby]

So are you saying that he's really supposed to double that 1.8 amps per phase when setting the driver current?

[ger21]

No, but I think they're saying that you didn't actually answer the question.