MotionBench electronicsTest and identify

Stepper motor

Also called NEMA-17, hybrid stepper, unipolar stepper.

Moves a known angle per pulse. Older printers, scanners, and floppy drives are where the good ones are. Many new inkjets switched to brushed DC plus an encoder strip.

If you are new to this category

These parts spin, push, or pump. A motor is a machine that turns electricity into turning. Some start turning as soon as you connect a battery. Others look identical and will not move until a small circuit tells them which coil to power next. The label, or the number of wires, is how you tell them apart.

Count the thick wires before you apply power. Two wires usually mean a brushed motor that can run from a battery. Three thick wires usually mean a brushless motor. Keep the board that came with a brushless motor.

Finding the coils

A stepper motor moves a fixed angle each time you pulse it. The wires are the ends of coils. A meter on resistance finds the pairs: two wires that read a low resistance are one coil. Wires from different coils read open, like a broken wire.

Specification. The right-hand column is what is typical. The label on the part in your hand wins if they disagree.
What to look for	Usual figure
Step	1.8° (200/rev) on hybrids from laser printers. 7.5° or 15° on cheaper appliance motors.
Wires	4 bipolar, 5 or 6 unipolar, 8 if both ends of each half-coil are brought out
Current	Printer NEMA-17 class is often 0.5–1.5 A/phase. The frame size does not tell you the current.
Frame	NEMA-17 (42 mm) is common. NEMA-23 shows up in larger copiers. Measure the face; do not assume.

Volts are electrical pressure, amps are how much current is flowing, and ohms are how hard the part resists that flow. A higher voltage than the part was built for is how salvage parts die on the bench. If a cell in the table says “read the stamp”, that stamp is the whole specification.

What people actually use it for

Axes on a small machine
Indexers
Anything you do not want to add an encoder to

Leave this one when

Detent is rough, a cable is cut with no pinout, or you needed holding torque the motor was never rated for. A hot stalled stepper is just copper loss.

Buying a new one is the better idea when

A new NEMA-17 with a datasheet, once you are past the prototype and the current matters.

How to tell if this one still works

Find coil pairs with a meter. Equal resistance within a pair, open between pairs. Then a chopper driver, not a battery across a coil.

Step-by-step on the bench: Pair the coils on a stepper

Tools you will want: Meter, Stepper driver.

Words on this page

Short meanings, so the rest of the entry is readable if you are not already doing this every weekend.

torque: Twisting strength, as opposed to speed. A gearbox trades speed for torque. That is why a drill can turn a screw slowly with force.

Where people actually find it

4 notes, most useful first. “Leave it” means the part is in that machine and you should not take it: it is dangerous, worn out, or only useful if you already know that exact repair.

Harvest at a glance
From	Call	How many	How often	Where it sits
Laser printer	Prize	2–4	usually	Paper path and drum drive.
CD / DVD / Blu-ray drive	Worth it	1	sometimes	Sled, on older drives.
Inkjet printer	Worth it	1	sometimes	Older and higher-end machines, paper feed.
Flatbed scanner	Worth it	1	usually	Carriage drive.

Prize — take this firstLaser printer2–4 · usually
In this particular machine
NEMA-17 class hybrids are common on older machines.
Where to look
Paper path and drum drive.
How to get it out
Take the connector. Note the current on the driver if it is printed.
The condition to expect
Good.
Worth pullingCD / DVD / Blu-ray drive1 · sometimes
In this particular machine
Small, often a fine step angle, low current.
Where to look
Sled, on older drives.
How to get it out
Keep the lead screw if you want the linear motion.
The condition to expect
Good.
Worth pullingInkjet printer1 · sometimes
In this particular machine
A real hybrid stepper when it is present.
Where to look
Older and higher-end machines, paper feed.
How to get it out
Keep the connector and count the wires.
The condition to expect
Good.
Worth pullingFlatbed scanner1 · usually
In this particular machine
Or a DC motor. Both show up.
Where to look
Carriage drive.
How to get it out
Take motor and belt as a set.
The condition to expect
Good.