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Choice of a Stepper Motor Driver

Skire44

Jun 24, 2015
2
Joined
Jun 24, 2015
Messages
2
Hello,

I am currently working on project in which I have a 40N/cm-12V-1.7A/phase Stepper motor which has to lift a 108g piece at 1.4cm of the shaft (at that distance the motor is supposed to be able to lift 2.8 kg). I did the mistake to choose an Easy-driver (https://www.sparkfun.com/products/12779) to control it, which is limited to 0.75A/phase. I tried to used it, the motor turn but as soon as a quite low torque is applied to the shaft, it is blocked. I checked the output current/phase of the driver and this one is directly going up to a maximum value of 330 mA when the shaft is blocked (1 mA otherwise).
My first question is then why does this maximal current is 330mA and not 750mA? Did i misunderstood the documentation of the easy driver which is able to supply output voltage of 6V up to 30V and in fact 750mA is only for an output voltage of 6V?
(I precise also that i supply my driver with a 7.5-1500mA-18VA supply which should be enough)

My second question is then if I chose the Big easy driver (https://www.sparkfun.com/products/12859) or the AMIS-30543 (https://www.pololu.com/file/download/AMIS-30543-D.pdf?file_id=0J869) which are both announcing an output current/phase of 2 A with output voltage of 6V up to 34V, will I really have this 2A current of each coil of my 12V motor?

Thanks for your attention, hope that someone will be able to help me.

Regards
 

Minder

Apr 24, 2015
3,318
Joined
Apr 24, 2015
Messages
3,318
The current to a stepper should be be controlled by the stepper drive to remain constant throughout the rpm range, this is achieved by a using a high than rated stepper voltage and PWM to control the mean current to this level.
If the current is exceeded burn out can occur, less than rated results in low torque.
M..
 

Skire44

Jun 24, 2015
2
Joined
Jun 24, 2015
Messages
2
The current to a stepper should be be controlled by the stepper drive to remain constant throughout the rpm range, this is achieved by a using a high than rated stepper voltage and PWM to control the mean current to this level.
If the current is exceeded burn out can occur, less than rated results in low torque.
M..
Thank you minder but that doesn't really answer to my question, I know that the lack of power is due to my driver, I just want to know why that current is not the one indicated (or if I understood the indications in a wrong way) and if the use of one of the more powerful driver that I indicated will be enough.

Regards
 

Arouse1973

Adam
Dec 18, 2013
5,178
Joined
Dec 18, 2013
Messages
5,178
Hello,

I am currently working on project in which I have a 40N/cm-12V-1.7A/phase Stepper motor which has to lift a 108g piece at 1.4cm of the shaft (at that distance the motor is supposed to be able to lift 2.8 kg). I did the mistake to choose an Easy-driver (https://www.sparkfun.com/products/12779) to control it, which is limited to 0.75A/phase. I tried to used it, the motor turn but as soon as a quite low torque is applied to the shaft, it is blocked. I checked the output current/phase of the driver and this one is directly going up to a maximum value of 330 mA when the shaft is blocked (1 mA otherwise).
My first question is then why does this maximal current is 330mA and not 750mA? Did i misunderstood the documentation of the easy driver which is able to supply output voltage of 6V up to 30V and in fact 750mA is only for an output voltage of 6V?
(I precise also that i supply my driver with a 7.5-1500mA-18VA supply which should be enough)

My second question is then if I chose the Big easy driver (https://www.sparkfun.com/products/12859) or the AMIS-30543 (https://www.pololu.com/file/download/AMIS-30543-D.pdf?file_id=0J869) which are both announcing an output current/phase of 2 A with output voltage of 6V up to 34V, will I really have this 2A current of each coil of my 12V motor?

Thanks for your attention, hope that someone will be able to help me.

Regards

The answer to your first question is the factory pre-set for the output current is 330 mA. You need to change R16 on the PCB to achieve 833 mA, I think it's a POT. The ref pin voltage for max current is 5 volts. Try this first before choosing another device.
Adam
 
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