Re: wave drive

Hello,

You've got a lot of good replies already... (But I'm not usre anybody
answered YOUR question?)

As Mariss says, wave drive is just turning on one coil at a time,
1,2,3,4,1,2,... It is a method of FULL stepping.

2 phase on full stepping gives more torque. Coils are energised in a
1&2,2&3,3&4,4&1,1&2... pattern

Half stepping combines these two: 1,1&2,2,2&3,3,3&4,4,4&1,1,1&2...

The reason I think you are asking this question is that you have read
somewhere that wave drive is used for high speeds. Which WAS true,
when that was written!

Back when unipolar was king, and transistors were expensive enough
that you wanted to use 4 instead of 6, and 6 instead of 8, wave drive
WAS a faster way to drive the steppers of that day. That's because in
wave drive, there is a lot of TIME between switching of a given
transistor (except during reversal of direction!). This meant that
the typical high inductance motors of the era had time to "empty"
their windings. By the time you got back to it, you weren't fighting
the electrons you'd just stuffed in on the last go-round...

So someone wrote it down, and you read it, and now the experts have
weighed in with the CURRENT status of things. BUT...

Since you've asked, I'm gonna assume that you're using a drive
circuit FROM the past? And perhaps an older surplus high inductance
motor as well?

Now IF these two things are true, the answer to YOUR QUESTION is:

Wave drive is fastest.

A second factor nobody else mentioned needs mentioning now. In
the "old days", getting the pulse stream out quickly was also harder
than it is today. So the fact that wave drive moves twice as fast for
a given pulse rate is/was also a factor. And tho' the excessive
ringing that Mariss mentions IS a problem (compared to half stepping,
which you gave as your other alternative), you can cover more ground
more quickly with wave drive IF your pulse train is speed limiting...

Finally, Art mentioned some things about step/dir versus direct phase
drive(which maxNC uses), which may be misleading. As you probably
already know, step/dir is a separate thing from wave drive. You can
have individual port bits driving the phases in either wave drive OR
half step. And you can have step/dir driving the motor in wave drive.

My guess is that you are using the UCN5804 chip and documentation?

Hope these answers are helpful,

Ballendo

P.S. While the new stuff often works better, the old stuff still
works. And IF your application is set up for the "old stuff", it can
work VERY WELL. AND very inexpensively! (Yes, you CAN build a "real"
240IPM gantry router using unipolar drives... one canadian Mfr. did
it for years, and many of those machines are still working today.)

--- In CAD_CAM_EDM_DRO@yahoogroups.com, asigraph@b... wrote:
> hi
> i have a question about stepper motor
> if i need high speed from unipolar motor do i need
> 1 wave driving
> 2 half step
>
> 2 what is the benefit of using wave driving?
> hope to get answer quiqly i finished my machine and decide which
way
> to drive it (the best way)
> thanks asi