Re: How can you test a stepper ?

Dave,

If these are 5,6, or 8 wire motors, you can test 'em with my simply
made Graphical Universal Unipolar Tester (GUUT, pronounced "goot")<g>

You need a pine board (or short piece of 2x4), some paper clips,
thumbtacks(without paint, and made of metal-in other words, CHEAP)
Some hookup wire (#16-22 or so), and 2 "D" batteries (optional: 4-
1n400x series diodes needed for 2 phase on and half step testing)

You can use drywall screws instead of thumbtacks. Nowadays the screws
might be easier to get than the thumbtacks without paint.

Now we'll breadboard:

Open six paper clips to 90 degrees(pull the small "loop" up form the
big loop outside it). Put the batteries on the board in series(as in
a flashlight), and use 4 of the 6 paperclips as "brackets" to hold
them in line, holding them down with screws or thumbtacks. Fasten the
other two paperclips to the board so that they provide contact to the
batteries ends. Put a 12 inch or so piece of hookup wire under the
tack or screw on these two clips, before you tighten it down. You've
now completed your GUUT stepper tester power supply!

Next we'll build the translator/phase select portion. This section
will be capable of wave drive, and one phase or two phase on full
stepping. It will also allow half stepping. It uses an
advanced "wetware" translation device :

Put 4 screws or tacks in the board in a row about an inch apart from
each other(again put 12 inch or so hookup wire under these before
tightening. Now open 4 paperclips 150-170 degrees, and arrange them
parallel to each other, such that the big loop end is over the screws
you just placed. Next begin fastening the small loop ends of these
clips. Before fully tightening them, put either a short wire under
each fastener, OR one end of a diode. Be sure that you put the
same "end" of each diode towards the clip.(the diodes have a "band"
at one end; be sure all these bands are either towards the switch, or
point away from it.

If you have used diodes, then attach the 4 short wires(3inches or so)
to the other end of the diode by twisting the two together. Now bring
all of these 4 wires together, AND one of the battery ends, and twist
them so that they maintain contact with each other.

Your GUUT is now ready for use!

Note: The diodes are not necessary for testing whether a motor is
good or bad, only for playing with "advanced" half-step and 2phase on
stepping techniques.

Using an ohmmeter (or mfr. specs), determine which of the wires is
the center tap in the two motor coils. Connect these two motor wires
to the GUUT battery end which is not already connected.
Now connect the other 4 wires (6 wire motor assumed) to the wires
coming from the GUUT paperclip SPST "switches".

The motor at this point should be "locked up". adding a masking
tape "flag" to the shaft can be helpful.

Now, if the motor is good, "SOME" combination of tapping the 4
switches will make it turn correctly in one direction. If you number
the switches 1-4, it will make the discovered pattern more remember-
able... (If no combination makes the motor turn consistently, either
you have a bad motor, or you used diodes and you need to reverse your
batteries in the "holder"...)

start by trying the obvious, which is 1-2-3-4,1-2-3-4... If this
works, then try 4-3-2-1,4-3-2-1... and the motor should turn the
other way, also smoothly

If not, keep tring combinations (one switch activated at a time),
until you get one which works. Let's say you have found that 3-1-4-
2,3-1-4-2 works. Now try 2-4-1-3,2-4-1-3, and the motor should
reverse.

At any rate, if you can find a combination of switch presses which
make the motor turn correctly, you have shown that the motor is
GUUT<G>.

For the next part, you may want to reconnect the motor so that the
weird combination you have found becomes 1-2-3-4. What I mean is,
using the example above, where 2-4-1-3 worked: move the motor wire
connected to 2, to switch 1; the one connected to 4, to sw2; the one
connected to 1, to sw3; and the one that was connected to 3, to sw4.

As a side benefit, you now have the motor leads identified for
hooking up to a commercial drive<G>

Any way, now you can try some other stepping variations (if you have
included diodes in your GUUT).

What you have done so far is called single phase fullstep wave drive,
or just wave drive. That is, 1-2-3-4,1-2-3-4. This is used for high
speeds, but has less torque than:

Two phase on, fullstepping, which is: 12-23-34-41,12-23-34-41
(pressing two switches at a time) Going the other way is 41-34-23-
12,41-34-23-12

You may or may not be able to tell that this 4 step sequence is not
giving the same step positions as the wave drive 1-2-3-4 that you
used first.But that difference is what allows us to:

Half step. Which is 1-12-2-23-3-34-4-41,1-12-2-23-3-34-4-41, and its
reverse; to go the other way.

Es GUUT, yah?

Ballendo


P.S. I've had a bit of fun here, but what I have described is a quick
and easy way to not only see if a motor works, but also to viscerally
understand what a stepper driver is doing. When you are the
translator, and can feel your fingers tappingout the step sequences,
it is amazing how much clearer these basics become...



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude
<davemucha@j...>" <davemucha@j...> wrote:

> Interesting idea.
>
> Some are hard to turn, some easy.
>
> all lock up tight when just connected to the Gecko, even without

any

> steps. I assumed that was an indication of good operation.
>
> Dave
>
>