Unknown specification NEMA 17 stepper motor

Hi,
I found some used stepper motors from streets of our local electronics market, which are in working condition.
All I know about those motors are
1. NEMA 17 form factor
2. 2 phase bipolar (4 wire)
3. coil resistance 2.1 ohm.

Now as per Ohm's law if I assume that its current rating is ~1.5 A (which I think more of a standard in these types of motor), then the voltage rating comes as ~3.15 v (2.1*1.5).
I understand that I have to use constant current chopper driver, that would reduce the driver at standstill mode, and increase voltage while running.
The question is which driver I safely use to drive these motors. Can DRV8825 be an option? If so what psu I should use to drive it. Can I use a Computer SMPS?
Additionally I have a L293d shield. Can I use this shield at least to drive the motor to see it running. Can I add a small hi power resistance with the motor coil in series to achieve this?

Thanks in advance.
Debojit

Edited 1 time(s). Last edit at 08/22/2017 09:13AM by debojitk.

You can almost certainly use them. Don't assume they are 1.5A. Instead, look through this list [www.omc-stepperonline.com] for a motor with about the same resistance and length as the ones you found.

DRV8825 drivers should be OK, however they have problems with some types of motor so are best avoided unless you already have them. L293d is no good.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hi,
Thanks a lot for your suggestion.
Matching with my spec I found Nema 17 2.1 Ohm bipolar. It says the input voltage should be 2.8 volt.
I read that for DRV8825 the Vmot( min ) is >4v. So how this driver would be able to drive this stepper. I am confused here. Please help.

Thanks,
Debojit

Quote
debojitk
Hi,
Thanks a lot for your suggestion.
Matching with my spec I found Nema 17 2.1 Ohm bipolar. It says the input voltage should be 2.8 volt.
I read that for DRV8825 the Vmot( min ) is >4v. So how this driver would be able to drive this stepper. I am confused here. Please help.

Thanks,
Debojit

I hadn't seen that part of the datasheet, perhaps they added it in a later revision. I think that limitation is to avoid the known problem with DRV8825 drivers. So pick a different type of driver.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42

Quote
debojitk
Hi,
Thanks a lot for your suggestion.
Matching with my spec I found Nema 17 2.1 Ohm bipolar. It says the input voltage should be 2.8 volt.
I read that for DRV8825 the Vmot( min ) is >4v. So how this driver would be able to drive this stepper. I am confused here. Please help.

Thanks,
Debojit

I hadn't seen that part of the datasheet, perhaps they added it in a later revision. I think that limitation is to avoid the known problem with DRV8825 drivers. So pick a different type of driver.

I was reading through some blogs and post and found that there is a pot to adjust Vref which is related to output current. To keep the current constant it automatically adjusts the voltage to each phase. Could you please confirm if it is the case?

Thanks,
Debojit.

Plug-in drivers generally have a pot to adjust the motor current. 3D printer control boards with built-in stepper drivers generally provide for setting the motor currents using a gcode command, which is easier.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].