half-stepping vs. full-stepping

I've been searching the forums for information on half vs. full stepping and haven't had any luck. I know it's been discussed before though.

I'm new to electronics, but from what I've read, half-stepping means the motor will take twice as many steps to complete a revolution, thus giving precision on positioning, but doesn't this also make it twice as slow?

I'm about ready to start soldering the stepper motor boards, but step one is to set it to full or half stepping... and quite frankly, I have no clue which is better, and more importantly, why (when it comes to RepRapping).

Thanks

-John

Yes, it will be twice as slow (assuming you take the same step speed, which is likely). To see the difference, imagine there are two coils, one pushing and pulling in the x direction, one in the y. For full stepping, one would pull Y, then pull X, then push Y, then Push x, before repeating the cycle. The internals of the motor would make one revolution (which would rotate the spline a smaller distance, 1/50th of a rev for a 1.8 degree motor).

For half stepping, the motor would do x+ , x+Y+, Y+, x-Y+, x-, x-Y-, Y-, x+Y-, for a cycle. For the half steps, two coils are energized. This creates more torque on the halfs, at the expense of more current.

You can also do full-stepping by energizing two coils as well:
X+Y+, X+Y-, X-Y-, X-Y+

Hope that helps.

Hi John,

... try serching "halfstepping / [All Dates]" for two results or "microstepping / [All Dates]" for 3 sides full ...

For the speed - with halfstepping you can apply doubled frequency too, so it's not so bad.

With fullstepping i'm driving with 1-1.5kHz max., halfstep -> 2-6kHz and with microstepping i'm driving with 10kHz - only because my driver can't clock faster

Viktor

The limiting speed of the motor is when inductance prevents the current rising fast enough.

Full stepping gives a higher maximum speed for a given motor and load, but half stepping gives better resolution and smoother running at low speeds. It is not uncommon to switch between the two when the hardware allows it.

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[www.hydraraptor.blogspot.com]

Thank you for the information. I suppose what was confusing me is what would be better for my first try.

Am I inferring appropriately that with half-stepping, my builds will run slower, but the quality should be higher?

If so, sounds like I ought to opt for half-stepping for my first time around, then maybe once I have some experience, dabble with optimizing things.

Thanks.

John,
You didn't say what mechanics you are using. For Darwin I think half stepping is used for X and Y for precision and full step for Z for speed. That is because X&Y are belt driven, so are plenty fast enough, and Z is screw drive, so is slow.

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[www.hydraraptor.blogspot.com]

Hi Nophead,

As I'm too lazy to modify my stepper board for full stepping (half stepping is now wired/soldered in, I decided to simulate full stepping by doing two steps in very quick succession (10 µs apart). The L297 seems to keep up fine with the double steps rate, and I trust that the switch is so quick, the motor or driver won't be affected much. To my surprise, I haven't found much if any difference yet in maximum unloaded speed. I can do either 1700 half steps per second, or 850 full steps. I'll have to double check my setup on monday to make sure I'm doing everything right. I may also put some jumper pins instead of the solder pad on my board.

What speed difference would you expect driving steppers with half step or full step?

-Geert

Stepping twice should work but you have to keep the firmware in sync after the L298 is reset, otherwise you could inadvertently switch to wave mode if the Arduino is reset, i.e. one coil on instead of two.

With half step you turn a coil off, wait for the field to collapse, then energise it the opposite way and wait for it to build up. It should be quicker to just reverse it. You will only notice if you have acceleration though. The pull out rate is the speed that is limited by inductive switching. That is always faster than the pull in rate, which is the fastest speed you can start at due to inertia. With no acceleration the speed is going to be limited by the pull in rate.

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[www.hydraraptor.blogspot.com]

Yes, I made sure to keep things in sync. (Those LEDs on the stepper board are very handy, I'll bring out the "home" signal of the L297 soon.) Anyway, my findings are that there is little difference between either half, software-emulated full and hardware full stepping. This is on an unloaded system. Essentially, I'd recommend to always use half stepping. Even if you don't need the resolution, the stepping rates are low enough to be easy to manage even at half step, and at low speeds things are smoother with half stepping.

-Geert

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See [web.mac.com] for my repstrap blog with stepper tests

I am waiting for my full kits of the new rrrf Stepper Motor Driver v2.3 to arive..

I am also playing with the A3980 1A microstepping stepper driver from Alegro I think these will be very interesting may be with the 16x microstepping ability...

We can look at 7.5 degree stepping motors yet still maintain the resolution and acuraxcy

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Bodge It [reprap.org]
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BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

BodgeIt Wrote:
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>
> We can look at 7.5 degree stepping motors yet
> still maintain the resolution and acuraxcy
>
I'll be interested to see if you can microstep a tin can stepper. I don't think you're going to be able to.

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

I have made the asumption that the fields and stator will behave in the same way as with the smaller step devices.

Please explain your doubt further as it would be silly for me waste time on this line of thought if there is not a chance in hell of achieving the goal.

I left school at 15 so I do not have the benefit of all the complex theory involved in calculating if the magnitude of the fields would overlap enough on a 7.5 degree step device to be able to resolve a step < a half step.

I could say in self defence that quite often my crazy ideas do work though.

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Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

oops I am making the assumtion tha you can half step a 7.5 degree stepper

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Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

I am not quite finished with my repstrap, and I am using unipolar steppers but I plan on running mine in High torque mode (AB, CB, BD, DA) I am not sure if this i s possible with a bipolar stepper though, but it gives me the resolution and speed of a full step with extra torque. The resolution is no problem because I am using 1.8 degree steppers with 1/4 20 lead screw so I expect to get high res slow prints (79 steps per mm).

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