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Full Stepping/Half Stepping

Posted by Jeff B 
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Jeff B
Full Stepping/Half Stepping
November 15, 2009 10:44AM
I have been looking through the documentation of the stepper drivers and the mother board for gen 3 electronics, and I can not find any reference to the Gen 3 stepper drivers being full of half step.

I am using the firmware from: [reprap.svn.sourceforge.net] which seams to be the newest 5d firmware

Is there a way to switch between full and half step?
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Triffid_Hunter
Re: Full Stepping/Half Stepping
November 15, 2009 05:45PM
the stepper driver v2.3 uses the A3982 driver chip. this chip supports full step and half step.

the v3.0 stepper drivers from makerbot use the A3977 chip which has built-in 1/8th stepping. I'm redesigning this board at the moment to accept the TSSOP28 package of this chip, which is significantly cheaper as well as pin-compatible with TI's DRV8811
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jeffrey b
Re: Full Stepping/Half Stepping
November 15, 2009 06:48PM
How do you change between full and half?
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Triffid_Hunter
Re: Full Stepping/Half Stepping
November 15, 2009 07:43PM
[www.google.com]

datasheet page 6 says it depends on whether MS1 pin is high or low
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Jeff B
Re: Full Stepping/Half Stepping
November 15, 2009 07:59PM
Thank you, I had looked at the data sheet and did not realize that H and L meant high or low. makes since now, thanks
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stephen george
Re: Full Stepping/Half Stepping
November 15, 2009 11:20PM
Sorry to ask a daft question but what are the benifits of 1 step
rather than 2 half steps?

Do you get more speed ? reliability etc

Stephen
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annodomini2
Re: Full Stepping/Half Stepping
November 16, 2009 07:27AM
stephen george Wrote:
-------------------------------------------------------
> Sorry to ask a daft question but what are the
> benifits of 1 step
> rather than 2 half steps?
>
> Do you get more speed ? reliability etc
>
> Stephen

Speed the stepper drivers have a limited frequency response so at full step you can move the motor much faster than at half step.
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VDX
Re: Full Stepping/Half Stepping
November 16, 2009 07:40AM
... the mechanics define the maximum speed of the motors, so for some specifics you can drive faster with half- than with fillstep.

My CNC-mill-controller is capable of 10kHz max. clocking speed - with fullstep an ramping i'll get max. 2kHz safe ... with half-stepping i'll get max. 6khz.

So when calculating: - with fullstep at 2kHz and 25microns stepping over 200steps or 5mm per turn i'll receive 2000x0.025mm = 50mm/s ...

... at half-step and 6kHz i'll get: 6000x0.0125 = 75mm/s!

Viktor
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Jeff B
Re: Full Stepping/Half Stepping
November 16, 2009 09:33AM
It also effects the resolution right? Or have I misunderstood?
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VDX
Re: Full Stepping/Half Stepping
November 16, 2009 10:02AM
... half-stepping means the motor can stop between the 'fullstep-positions', so the resoultion is doubled.

But the position is only so exact as the magnetic orientation between the rotor-teeth and the magnetization of the stator-teeth and is something 'elastic', so the absolute accuracy is depending of load or external forces, friction, damping or such ...

Viktor
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annodomini2
Re: Full Stepping/Half Stepping
November 16, 2009 11:26AM
Ahh, full step causes a different resonant frequency within the mechanics?
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Jeff B
Re: Full Stepping/Half Stepping
November 16, 2009 02:06PM
So I can assume by looking at the schematic that pin 12 on the stepper driver 2.3 is high by default, resulting in the driver being in half step mode?

Thanks for all the very informative information.
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