Unipolar stepper to bipolar stepper

Hi guys

I want to change this 5 wire unipolar stepper to bipolar.

As in the picture the center red wire has thin copper wire connected to it, from what I have read i just need to cut them?

But i see it has 2 thin copper wires connected to the top left of the red wire and there is two more connected to the bottom right of the red wire.

Can I just cut them?
Wont they be loose inside and short?


I could not advise you based on that photo.

Having wires floating around inside a metal case is not a good idea.

Also you would need to be able to access the cut wires so you could test the resistances with your multimeter to be sure that disconnecting the wires has the required effect.


If you can identify all the wires and which windings they belong too you can separate them and turn the thing into a 4, 6 or 8 wire motor - if you can't identify them you'll simply trash the motor - there doesn't look to be enough room to resolder any of those wires anyway.

What is the winding resistance? If its high (20+ ohms) there's little point converting the thing to bipolar, you won't make it faster, just more expensive to drive. You might get a bit more torque for the same input power with a whole winding being driven.

Hi Mark

It seems to me that the red wire is soldered over two points so I could possibly just heat up the soldering and split the two points and remove the red wire.

I dont know what the winding resistance is, there is no datasheet available online, to test it I need to split it first?

Im not too worried about speed, I just have a bipolar driver on hand and yes I would like a little more torque.

Another thing is I have been driving it with a uln2003APG at around 13v, 1 amp ac power adapter but the stepper gets so hot after 5mins I cant touch it for more than a second or 2?

Any idea what causes that?


Any idea what causes that?

The current flowing through the wires.

Stepper motors are often designed to run quite hot (80 C or higher) but without a data sheet...

You can measure the resistance between any wire and common now, no need to split. That's half of one phase winding. If you successful split the windings apart to a 6 or 4 wire configuration the phase resistance will be twice that since its two half-windings in series.