Stepper Motor, with no data sheets available

Please bare with me as this is my first time on board.

I have a couple of stepper motors that I removed from an old Epson printer that i wish to experiment with on my Adruino Mega 2560 R3 board. my problem is I can't find any data sheets for this motor, it is a STP-42D163 from Shinano Kinshi co. Does anyone have experience with this motor?

The motor is probably intended to run on somewhere between 5 to 12 volts.

To start, describe how many wires there are, and if you can, measure and post the resistance between all pairs. The lowest value is the coil resistance and that will give an important clue as to its current requirements.

the motor has four wires, 1 blue and 3 gray

Well, that is one nugget of information.

If you are interested in using motors and do not know how to measure the winding resistances, or don't have access to a multimeter, now is the time to get one and learn how to use it. A multimeter is an essential piece of test equipment and an extremely valuable learning tool.

Here is that other nugget of info

I measured between the following wires with wire 1 being the blue wire
wires 1 & 3 = 8.5 ohms
wires 2 & 4 = 8.5 ohms

Well those are the phases, the wires with the resistance that is.... each of those two pairs is one half of the motor.

So if you take some power, say 12v as a guess, and put it across one phase you'll get the motor to a certain point. Then put the volts on the other phase, guessing the polarity, then the motor might step. If it doesn't reverse that polarity. Then put the power back on the first phase, with polarity reversed from the first time, it'll step again. Finally back to phase two, but reversed from the second step.... mess around for a while and you'll see you'll get the motor moving with that manual application of power.

You might get this for example:

1  2  3  4
+     -
    +     -
-     +
   -      +

Thank you for the info I do appreciate it,

I can now tinker with it with out the fear of burning it up

Also maybe just start with a lower voltage I suppose... jremington suggested 5-12 but also some printer motors are 24. It should move (I think 8) ) at lower voltage, at least for testing purposes.

Once you've got it sussed, you can do that polarity changing with 4 Arduino pins, not that I mean you hook the Arduino directly to the motor wires. You need a chip in the middle, like maybe a L293 or something more modern, which has the motor supply voltage supplied to it. Then you control the chip's inputs from Arduino, and it in turn outputs the motor voltage on its output pins to the motor. So the chip output follows the Arduino control, but at the higher motor supply voltage.

I'm looking for a thread I wrote a while ago.....

Right on, starting with lower voltage is a good idea. I still have the circuit board and the power supply to from the printer, wondered if I can harvest that chip from it? and use the power supply?

Here is that thread.

Depending on your motor, the 293 might not be the right technology but I suppose it'll work to show the principle. Read that other thread I linked to in my linked thread.

Disclaimer: E&OE, YMMV, Ts & Cs apply....

You may find that the board from the printer uses a 293 EDIT: 297 AND a 298.... it would be good if you could use whatever it is, especially if you can read the part number and find a datasheet

Very helpful thread in your last post, Jimbo!

I would add that at 24 volts, that motor will consume about 3 amperes per winding and older technology like the L293/L298 can't handle that much current. The motor should work well on anywhere between 5 and 10 V, though.

Modern chopper motor driver boards like the Pololu version of the A4988 or DRV8834 chips are asier, more versatile and safer to use. Pololu - DRV8834 Low-Voltage Stepper Motor Driver Carrier