Hey DaBooBear,
you will always find them on the datasheet. If you get not datasheet with it, I would stay away from the item. However if the stepper has only four wires, it is possible to find out the wiring (see below).
A very good document for understanding how to wire stepper motors is
If your stepper has four wires, it says:
The trick is figuring out which wires make up the coil pairs. Here’s three ways to figure this out:
- Find the documentation for the motor. Assuming you don’t already have it, read the model number off of the motor and then search for it on the Internet. With a little effort, it is usually possible to get a datasheet for the motor. The datasheet will usually specify the wires by A+, A-, B+, and B-, or at least show which wires by color attach to which coils.
- If you can’t find the datasheet, but have an ohmmeter, measure the resistance between any two of the motor wires. If you measure a near short, then that pair makes up one coil, and the other two wires make up the other coil. If it is an open, then measure between the first wire and another wire and then to the fourth wire until you find a near short. Notice that I say near short because the coil is a long thin wire and has some resistance. Once the pairs are identified, then arbitrarily assign one pair as “A” and the other as “B” and arbitrarily assign one wire as “+” and the other as “-” within each pair. Then connect the wires as shown. There is a 50% chance that the motor will turn backwards when connecting this way. If it does turn the wrong way simply reverse one (not both) of the pairs and the motor will turn the other direction.
- If you don’t have an ohmmeter, most people can identify the pairs by feel. Stepper motor shafts turn fairly easily when the motor coils are open, but are more difficult to turn when a coil is shorted. First, leave all four motor coils open and turn the motor shaft to get a feel for how hard it is to turn. Then twist any two wires together. If the motor is significantly harder to turn, then you have shorted one of the coils and identified a pair. If not, disconnect the two wires from each other and connect a third wire to the first wire. If the motor doesn’t get harder to turn, disconnect the third wire from the first wire and connect the fourth wire. One of the combinations should be harder to turn and that is one coil and the two wires make up the other coil. Once the pairs are identified, then arbitrarily assign one pair as “A” and the other as “B” and arbitrarily assign one wire as “+” and the other as “-” within each pair. Then connect the wires as shown. There is a 50% chance that the motor will turn backwards when connecting this way. If it does turn the wrong way simply reverse one (not both) of the pairs and the motor will turn the other direction.
– Source: Wiring Stepper Motors - buildbotics
Further Information
Good video: (Disassembles stepper motor and explains its use very well):
GreatScott!: Stepper Motors and how to use them
Very good video (not to be missed):
Stepper Motors Advantages and Disadvantages
Very good page:
Stepper motor - Wikipedia
Further Video watching:
Precision motion control: ODrive Servo? Trinamic Stepper? Chinese Hybrid?