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Minimum pulse width for controlling stepper motor (bipolar) through PIC

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sankar.m8

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I want to control a stepper motor through PIC. Stepper motor is in bipolar mode. What should be the minimum pulse width(ON time and OFF time or frequency and dutycycle) needed for control..I couldn't find any details regarding this on the stepper motor datasheet.

Thanks in advance...
 

Iamventure

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Re: Stepper motor doubts

I want to control a stepper motor through PIC. Stepper motor is in bipolar mode. What should be the minimum pulse width(ON time and OFF time or frequency and dutycycle) needed for control..I couldn't find any details regarding this on the stepper motor datasheet.

Thanks in advance...
Hi,
The duty cycle is usually less than 50% to save power. For the stepper motor, you can have a 20% on time and 80% time and calculate the width based on the required speed. However, minimum pulse width shall be obtained only from the data sheet. Please share the part number.
 

alexan_e

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Re: Stepper motor doubts

The minimum width depends on the motor specification and supply voltage, you will not apply the same duty for 5v or 30v.
As the rotation speed gets higher you have to increase the duty cycle to keep the same motor current (because of the inductance) and there will be speeds where even 100% will not be enough to drive the motor with the rated current.
You have to use some kind of sense resistor to measure the current and change the duty to keep the current in the set value.

Alex
 

Iamventure

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Re: Stepper motor doubts

Hi, thanks alexan_e for the briefing. From Datasheet, the table gives an R of 6.6 ohm per phase for bi polar series connection. V = 5.6 V and I = 0.85 A.
Please calculate the pulse width for your target speed.
 

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