SM-E040

Six wire unipolar stepper motor. The two brown or black wires are the center taps, and should be connected to a power source (VCC or GND).

The other wires can then be sequenced to send current through one or more of the coils at a time. The simplest way I found to get the order right was to work out the inner connections using a multimeter. Measuring the resistance between any two wires will reveal one of three different results:

• The two wires are unconnected
• They have a small resistance between them (like 15 Ω or so)
• They have double the resistance measured between other wires (i.e. 30 Ω)

By measuring most of the wires this way, you can easily figure out which are the center taps, and which wires belong to which coil. Then if you build one of the following circuits on this page, you have only four choices for to wire up the four connections. You can see from the first schematic how each coil is supposed to be connected up, but the coils can be turned either way. Two of these ways will drive the motor in opposite directions (clockwise or counterclockwise), and the other two won't work. I used the following order, and my motor spun clockwise:

• Out2 - White
• Out3 - Red
• Out4 - Orange
• Out5 - Blue

This trick should work for any unipolar stepper motor, even if the connections/colors are completely different.