[image of digits]
Linear Stepper Motors

General Stepper Resources:

Stepper Motor Analysis:

  • Chart the resistance between every pair of terminals.
  • Draw a schematic beginning with the lowest resistance.
  • Mark the motor shaft with a pointer.
  • Tape the motor to a sheet of paper.
  • Apply a voltage across one pair of terminals.
  • Mark all the positions at which the shaft will stick.
  • Notes the terminals and polarities at those positions.
  • Do this for all possible terminals and polarities.
  • The paper should now show the complete excitation sequence and step size.

Yaskawa Electric, Japan, Linear Stepper Motor:

This was a custom device. The company could supply no information.

Carraige, removed from the rail and inverted, laying against the rail.
The brake electromagnets may be wired in series with the "coarse movement electromagnets."
What I assume are "fine movement electromagnets" magnetically engage tapered iron cores along the rail.
The outer-left and outer-right 30 Ohm coil are energized by the light-gray and dark-gray wires.
The left-center 30 Ohm coil is energized by the Blue and Yellow wires.
The right-center 30 Ohm coil is energized by the Blue and Orange wires.
The spacing of the "fine movement electromagnets" is less than that of the trapezoidal iron cores.
The "coarse movement electromagnets in black resin" are explained in the panels to the right.

Identifying the Coils:

With an Ohm meter, check the resistance between each pair of wires coming from the "coarse movement electromagnets" in the stepper motor. These are likely to be the heavier wires..

Resistance in Ohms between
each pair of leads
 
Green
Gray
White
Red
Green
        
Gray
 9.5      
White
 9.5 18.0    
Red
 9.5 18.0 18.0  

Beginning with the least resistances, sketch a "proximity" diagram. Clearly, Black is closest to Gray, White and Red, each pathway being 9.0 Ohms.. All of the 18.0 Ohm pathways exclude Black. This implies the following schematic:

Coil Activation: A 6-volt lantern battery, paper, tape, pencil:

Tape a long strip of paper to the track tightly, but loose enough to allow the carraige to move a few inches. Tape a piece of paper to the carraige and place an alignment mark on it. Activate each low resistance coil with the battery and note where the alignment mark on the carraige comes to rest on the long paper strip. Activate each coil with both polarities. Make sure to position the carraige so that the notations are near one another. The order in which the notations appear will give you the order in which you must activate the coils for forward or backward movement.

Note: On removing the connector, the wire noted as "B" for Black in the photographs turns out to be Green shrink-wrapped in Black.

Alignment Notations:

For fine movement, the activations shown by the six (6) curved lines in the alignment notations may be included, giving twelve (12) activations. The driver wiring for this arrangement would be complex..

Note: On removing the connector, the wire noted as "B" for Black in the photographs turns out to be Green shrink-wrapped in Black.

A fine twelve (12) step sequence.
 
Green
Gray
White
Red
Step 1
-
+
Step 2
-
+
Step 3
+
-
Step 4
-
+
Step 5
-
+
Step 6
-
+
Step 7
+
-
Step 8
+
-
Step 9
-
+
Step 10
+
-
Step 11
+
-
Step 12
+
-
A very gross, three (3) step sequence.
 
Green
Gray
White
Red
Step 1
-
+
Step 2
-
+
Step 3
-
+

Very gross unipolar movement may be obtained
from only three (3) activations, but it
is probably impractical.
A coarse, six (6) step sequence.
 
Green
Gray
White
Red
Step 1
-
+
Step 2
+
-
Step 3
-
+
Step 4
+
-
Step 5
-
+
Step 6
+
-

For coarse bipolar movement, the six (6) activations
shown by the horizontal lines in the alignment notations may be used.
Wiring a driver for this sequence is not excessively difficult.