microcontroller - Simple stepper motor circuit safe?

After various disappointments i finally understood how to find those damn wires on stepper motors. I tought it was simpler to drive bipolar motors but at the end i prefer unipolar stepper motors.. more cables but easier to drive.

Anyway... after breaking my only L293D i decided to try again with the famous ULN2803A. With some patience and low voltage (5v) i followed the previos mentioned video description and wrote down all the wire sequences of the stepper motors i have salvaged.

1. OKI EM-199 (SMA6511) from epson printer


2. OKI EM-154 (STK6711AMK4B) from epson printer


3. OKI EM-318 (LB1847) from epson printer



4. Mineba PM35L-048-HPI2 from hp printer


5. Mitsumi M55SP-1N from hp printer

As you can see i only found the datasheets of the motors that i could not find the drivers datasheet. So...

From what i understand the Mitsumi M55SP-1N:

1. consumes less: 259mA/phase


2. the excitation mode is the one used in the library 2-2 Phase excitation


3. and i know i can use 12v to drive it.

It's the first time i use a stepper motor

I don't want to destroy my microcontroller or any other part of the circuit.

And here is the question:

Am i safe using a ULN2803A to drive the Mitsumi M55SP-1N at 12v from 3,3v or 5v?

by that i mean:

1. the ULN2803A has already lots of protection diodes.. safe enough?


2. the Mitsumi M55SP-1N datasheet says 259mA/phase*4=1,1Amp..correct? uln2803 handles 500mA per channel and a max of 2,5A .....



3. powersupply of 1.25 Ampere....enough right?


4. A strange thing happend .. @5v with high speed stepping the ULN2803A got hot. 50-60 deg C. normal?

^{simulate this circuit – Schematic created using CircuitLab}

If its ok (safe) .... what Capacitor should i put near the Vin of the stepper motor?

And if you think i should use one of the above stepper drivers or know more about the unknown motors, i'm happy to learn new things...

Note: Like i said i already tested all motors at low voltage & low RPM, all of them work at 5v using the above circuit except the capacitors. This on a breadboard.. now i want to solder it together. I'm new to electronics, and something that, for you, is obvious, is probably something that i don't even know.