FYI stepper basics was Re: Stepper current in partial-step positions

--- In CAD_CAM_EDM_DRO@y..., mariss92705@y... wrote:
> Actually both coils carry the motor's rated current in full-step
> operation. <snip>

Full steps CAN be made with one coil on. It is called wave drive. If
you picture a very simple motor:

(a central bar magnet for a rotor, and four "magnet" coils, numbered
1,2,3,4 at 90° locations, like a clock face and putting coil 1 where
the 12 would be, coil 2 at 3 o'clock, coil 3 at 6 o'clock, and coil 4
at 9 o'clock)

, you can see that sending current to single coils in a
1,2,3,4,1,2,3,... pattern will cause the rotor to turn CW. To
reverse, it's 4,3,2,1,4,3,2... This is full step operation.

A SECOND way to do full steps is with two coils on. In this case the
rotor aligns midway between the two energised magnet coils. For
example, turning coil 1 AND 2 on will cause the rotor(of our simple
example motor) to position between the 12 o'clock and 3 o'clock;
coils 2 AND 3 will position between the 3 o'clock and 6 o'clock, etc.
So the patterns are:

1&2,2&3,3&4,4&1,1&2,... for CW, and 1&2,4&1,3&4,2&3,1&2,... for CCW.

Notice that the rotor (bar magnet in our example) aligns itself in
position(s) which are 45° from the "single coil full step" method.

Half stepping is COMBINING these two methods of FULL stepping.

1,1&2,2,2&3,3,3&4,4,4&1,1,... CW Now there are twice as many
positions (8) of the rotor.

Mariss knows this, and his answer is correct for the question given.
I didn't want any new members to become confused...

Hope this helps.

Ballendo

P.S. Since we're here: The examples above are using FULL ON and FULL
OFF for the coils.
Microstepping is simply using OTHER THAN "full" on and off for the
coils. If we put more current into one of the adjacent coils than the
other, the rotor will assume a position based on the magnetic
strength of the two coils (like a tug of war with a merry-go-round
when one person is stronger). This allows the rotor to be placed in
many positions BETWEEN the full step locations described above. IF we
use a sine/cosine relationship (as Mariss said) for determining the
coil currents, we will get smooth variation of postion between the
full steps.

Finally, if we just fed two sinewaves into the stepper coils, with
one advanced or retarded by 90° phase we would have
a "synchronous"(rotation speed is determined by the sinewave
frequency)motor. A capacitor is often used for this phase "delay" on
synchronous motors. In the USA, it would turn at 72rpm if run from
the typical 60 hz power outlet (I'M NOT SUGGESTING YOU DO THIS!).

The point is, a stepper motor is nothing more than a synchronous
motor running on square waves (full step operation). As we digitally
approximate these into sine waves to a finer and finer resolution, we
move to half step, then on to microstepping.