To turn clockwise & anticlockwise using : Arduino R3+Unipolar Stepper+ULN2803APG

Hi Experts,

I have little knowledge about electronics but really keen on working with microprocessors and controllers, i would like to make my 6 wired unipolar stepper motor to be turn clockwise & anticlockwise after few steps,
I got my circuit wiring and way to do it on the net except the chip may vary as i cant get exactly ULN2003 to make the stepper driver.

I had my basic code to turn the stepper first before moving further and its working but the ULN2803APG chip is getting very hot just after few steps.

I’m not sure which part went wrong, Is there IC chip is not compatible ? Wiring ? Or may voltage is more than the required (I’m also not sure what is my stepper voltage for my case I’m using 9v external dc power source,eventually i cant find the datasheet on the net for this particular stepper motor - 55SPM25D6F1.

I have attached my drawing for your reference. Could anyone out there assist me on this.

Thanking in advance,

Arduino + Stepper Motor.pdf (908 KB)

It's a 55SPM25 steppermotor, I think it's 12V.

First measure the winding resistance of the motor - is there any current, voltage or resistance information on the
motor’s ident plate?

The ULN2003’s power dissipation for a particular current can be worked out from the graphs on the datasheet
(saturation voltage is fairly high, its a Darlington device) - if you’re pulling more than a few 100mA it will need
a heatsink and only goes up to abs max of 500mA per pin anyway.

You are out of the current range of the 2003/2803. Consider TIP122(s) or MOS FETs

Hi LarryD,

Is the TIP 122 is power regulator, if yes where can I place it according to my circuit. Sorry if I'm asking some silly question as I'm not very well in electronics.

Thanks, starter_kid

Hi Krodal,

Thanks for the info.

Thanks, starter_kid

Hi Mark,

I have noticed on the motor stated as 9ohm only.
I have tested also by placing an LED on the coil end and by spinning the rotor the LED is blinking but didnt measured the voltage from the output.

As per your quote, i need a heat sink to solve the heat on chip is it.

I have re-attached the wiring circuit.


Arduino + Stepper Motor.pdf (908 KB)

The pdf file which was attached unable to be downloaded.
Replaced with a jpeg format.

TIP122 X 4 driving stepping motors

Note: in your wiring diagram there is no common ground to the Arduino.

I'm not connecting any ground to the board, infact i should right ?

Do the ground from my breadboard should connect to arduino ground ?

I just bought TIP122, will connect the ground to pin 1 (G) while where should the other 2 pin goes to (D) & (S)

Looking forward for replies,