Let's Make Robots!

Steppers found :) Trying to decide driver

I wandered past an old Brother MFC 9700 in the corridor and grabbed it.  Found two stepper motors, one from the Auto-document feeder and one that was moving the optical scanner. 

ADF motor: Mitsumi M42SP-6NPK.  I figure this little guy at 41.4 mN/m

Scanner motor: Shinano Kenshi STP-42D009. Wrote what I figured out about this in this older thread. Not totally sure but something like 200 mN/m or 30 ish oz-in.  makes sense as it is larger/heavier.

I think I'm going to drive them with the driver from Pololu.  Trying to figure out if I need the one with voltage regulation or without.  Anyone able to help me figure that out? AFAIK I connect from the GPIO pins to the DIR/STEP pins (I don't need to worry about micro-stepping). And I connect from my PoE power (~12-18VDC) direct to VMOT.

I think if I get the one with voltage regulators I don't need to connect a separate logic voltage (at 3.3 or 5) from the microcontroller board, it gets that regulated down from the VMOT input.  If I get the one without the regulators, I'd need to connect from a 3.3 or 5VDC connector on the RouterStation. Two 3.3VDC sources (UART and JTAG) even without using the USB connector, so I think that means I don't need to get the voltage regulated driver.

There are minimal wiring diagrams for the voltage regulated one and for the non-regulated one. My board is a 3.3 logic so presumably, on the voltage regulated one I'd wire 3.3V rather than 5V

 

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Thanks Dean, that's really helpful, I should dust off the math and figure out the inertial load :)  Over at this old thread on Steppers we think we've figured out that it draws a max of 0.9 amps.

I see that you already had a stepper page with much the same information (at least the English part -I don't read Chinese)

You said the stepper showed 5.2 ohms and you figured a current of 0.9 amps --By Ohm's law that would mean a voltage of 4.68 volts by my calculations. A 5 volt supply with 5.2 ohms would give (5/5.2 =) just over 0.96 amps.

[Of course there is also inductive reactance to keep in mind, but on these steppers I have not noticed it affecting things that much.]

Thanks Dan.  Love that Ohm guy, so smart :)

As I understand it (ie barely if at all) the driver can do active current limiting, so one can feed higher voltage while limiting the current.  Apparently that's how one gets micro-stepping out of these things.  I don't actually need micro-stepping so I'll probably be feeding 12-18v but current limited to 0.9 amps.

My understanding of the current limiting stuff comes from the section titled, "current limiting" on the driver info page.

I was concerned about how much current your motors would draw, especially the larger one. While searching for the info, I found this page with information on Shinano stepper motors.  Looks like there is some good information on stepper circuits there.

http://www.shinano.com/motors/docs/SKC_stepper_operation.pdf

 

Hope you find it useful.

Dan M

Went ahead and ordered the voltage regulated one, might come in handy down the road.  These drivers seem to put out more power than the EasyDriver from sparkfun and the comments on the Sparkfun one do suggest some manufacturing issues.  OTOH I could have gotten the Sparkfun one through Amazon Prime.  Hate paying for shipping and it still takes 3-5 days :)