General - Steppers: Determining Pinouts

Let's say you have a stepper motor, but have no idea which wires are which, or what to hook where. What to do??

All Parker stepper motors have two phases, which are alternately energized by the drive, causing the motor to spin. A 4-lead or 6-lead motor will have one coil per phase; 8-lead motors have two. We arbitrarily call one of these phases "A+/A-", and the other one "B+/B-".

Each wire in a 4- or 8-lead stepper motor is associated with one end of a coil. The first thing is to find out which wires are on the same coil. There is a simple way to do this: pick two random wires, and measure the resistance between them. If you get a finite value (on the order of a few ohms) then these wires are on the same coil. Continue until you have the wires paired up.

With a 6-lead motor, in addition to the four leads at the end of the phases, there are two center-taps--one wire that sprouts from the middle of each phase. This makes it easy to determine which two wires are the centertaps: the resistance from either end of the phase to the centertap should be half the resistance measured across the entire phase.

An eight-lead motor has two coils for each phase; these coils can be connected in series or in parallel. For now, just find which wires pair up with which (you should end up with 4 pairs). Then, find out which pairs are on the same phase . For this, you will need your stepper drive. Configure the drive to run at 50% current (if applicable, also set inductance 50%). Connect one pair of wires to the A+/A- terminals, and another random pair to B+/B-. If the motor spins, you have picked one coil from each phase. Good. Otherwise, the coils are on the same phase. In this way, you should be able to determine which coils are on each phase.
You now should have each wire paired up with its "coil-mate", and each coil paired with its "phase-mate"). Call one pair of coils "phase A" and the other one "phase B". Then, call one coil in each phase "coil 1" and the other coil "coil 2." You now have 4 coils: A1, A2, B1, and B2.

Now we must determine the polarity of each coil within each phase. Connect one A coil and one B coil to the drive, and command clockwise motion. If it spins counterclockwise, swap the wire in B+ with the one in B-. Now, you know the positive side of each of these two coils. Label these wires A1+, A1-, B1+, and B1-. Now, remove coil B1 and insert coil B2. Again, command clockwise motion. If the motor turns counterclockwise, swap the wire in B+ with the one in B-. Once it spins clockwise, label the wire in the B+ terminal "B2+" and the wire in the B- terminal "B2-". Finally, remove the A1 coil and insert the A2 coil. Command clockwise motion; if the motor spins counterclockwise, swap the wire in A+ with the one in A-. Label the one in the A+ terminal "A2+" and the other one "A2-".
You've now got all the leads labeled: A1+, A1-, A2+, A2-, B1+, B1-, B2+, and B2-. Here is the time to decide whether to hook it up in series or parallel configuration. Parallel wiring gives a higher torque at high speeds, but heat generation limits the motor's duty cycle to 50%. Series configuration allows the motor to be run constantly. Series is more commonly used.

Celebrate! Your motor should be running now.

And by the way, here's the most common color code for wires:

A1+ Red
A1- Yellow
A2+ Blue
A2- Black
B1+ White
B1- Orange
B2+ Brown
B2- Green