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Modifying 28BYJ-48 steppers to run off A4988 driver modules (like NEMA 17)


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I modify my 28BYJ-48 stepper motors to run off the A4988 driver modules, just like the Nema 17. I use these for remote focus for my astro imaging.

These motors come with centre-tapped coils with the centre-taps connected internally. We need the full coils without the centre-taps and these need to be separate so the internal link needs breaking and center-taps ignored. This in turn effectively changes a 5v rated motor to one that works fine with 12v.

These photos show the coils and connection PCB taken out of the motor, to explain the process. (Don't jump straight in and take the motor apart, it isn't necessary.)


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The yellow and blue wires are one coil (or winding) and the orange and pink wires are the other. The red wire is no longer used and cut short for safety.

At first I opened the motor casing to get at the connection PCB but it was very difficult to get everything back in so I decided to try and cut the PCB track without taking the motor apart.

I carefully drilled a hole through the blue plastic connection cover to access the PCB where the strip wanted cutting through. Then I was able to take a very small screwdriver and scrape through the track without disturbing anything else. This is shown in the close-up photo below. As before the coils are orange-pink and yellow-blue. Do not connect the red wire.


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Note :- Seems not all motors use the same colour wires but the outer two wires are one coil and the inner two are the other. The middle wire is not used and should be cut short and insulated for safety.

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Here is some more information on the 28BYJ-48 stepper motor.


My modification turns a unipolar motor just using half of each winding into a bipolar using all of each winding which provides a lot more torque and means a 5v motor can be used on !2v as I said earlier..

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That's really useful. I've done something similar with a big stepper but never thought of doing this to one of these little fellows.

The tip of drilling through the blue cover is well worth keeping!

Thanks Gina.

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