What is the best current range of 42 step motor? #define


Dave Schwartz
 

Start at 40% of the motor's current rating (look up the specs on the Internet). If the motors stall, increase by 10% but do not exceed 70%. If the motors still stall, you have a configuration problem where your requested slew rate is to high... reduce it and restart the current tuning at 40%.


On September 22, 2020 10:19:52 PM EDT, zslhg903@... wrote:
What is the best current range of 42 step motor for eq3d?
 

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zslhg903@...
 

Thankyou, So if the current is too low, the motors will stall.


George Cushing
 

Question from the depths of my ignorance; If I determine the resistance of a stepper's coils can I use Ohm's law to find the current needed by the motor? I assume things like back EMF and inductance mean I can't , but just want to confirm that. TIA


Dave Schwartz
 

Yes but Ohm's law has another variable: voltage. What is the rated voltage of the motor?

For most motors I have purchased, that number is not on the spec sheet (I do not know why, only one set came with a second sheet that had the voltage on it). Its not safe to assume 12V (the usual Ontep supply voltage) or 24V (the usual maximum) because that would give you a current value much higher than rated in inverse proportion to how much the rated voltage was below whatever voltage you chose.

For example, only one pair came with a sheet that showed the rated voltage of 5.4V and phase resistance of 6 ohms which does indeed come out to the rated .9A current. However, if I didn't know that voltage and assumed 12V, I'd get 2A which would quickly burn up my motors and drivers.

Some motors have rated voltages in the 2.5V range and the situation would be even worse.

On 2020-09-23 9:44 a.m., George Cushing wrote:
Question from the depths of my ignorance; If I determine the resistance of a stepper's coils can I use Ohm's law to find the current needed by the motor? I assume things like back EMF and inductance mean I can't , but just want to confirm that. TIA