I have 3 second hand bipolar (4-wire) motors, I found the data sheets on the www, but they don't show the color code of the wires. How can I test it in a safe way? I can of course measure which two wires form a coil. Can I hook up one coil at a time, give a step signal and see which direction it turns? Is this save, or is there a better / easier way?
Connect both coils up as they should be.
If the motor does not spin in the correct direction, reverse one set of the coil wires. This will cause the motor to spin in the opposite direction.
You should be good to go.