Stepper motor 28byj-48 5V from unipolar to bipolar

Other Hardware Motors, Mechanics, Power and CNC
1

Hi,
I follows this tutorial to convert 28byj-48 5V from unipolar to bipolar:

then i followed this:

to use the new bipolar motor with the arduino through the drv8825, i replicate the scheme with my components then I power the drv8825 with a 9V battery, i run the same code of the tutorial and I power all, but the motor doens't move and I hear a whistle from within the motor.

can anyone tell me What could I have done wrong?

thanks

2

Those small rectangular 9V smoke alarm batteries do not have the current capacity to drive a motor.

Also, you must set the current limit as described on this Pololu page.

3

groundFungus:
Those small rectangular 9V smoke alarm batteries do not have the current capacity to drive a motor.

Also, you must set the current limit as described on this Pololu page.

Thank for you answer, how much I have to set the current?

4

I have been working with a similar unipolar Airpax KB2224 (12v, 147Ω/coil). I have had no luck driving it with any of the Pololu type drivers. Most are rated for 1.5amp max output and that hasn't been enough to start the KB2224. Even a L295 4amp driver requires 5-7 amp power supply to to drive it a 400 RPM. These old designs have very small gauge coil wiring. I have a new 10amp Pololu type driver that I am going to try next.

You can set the amps for the DVR8825 with the potentiometer and a DMM's ammeter while powered by setting the probes at the A+ and B- motor terminals or between ground and the potentiomenter. This last gives you the voltage reference and you have to calculate the V-ref you need for your motor.

See this: Pololu - Video: Setting the Current Limit on Pololu Stepper Motor Driver Carriers

HTH, George

5

The 5 volt 28BYJ-48s I have show about 23 Ω per coil, so 217 mA @ 5V, yours will be double that, 46 Ω @ 9V = 196 mA. I would limit current to 150 to make sure the motor doesn't overheat.
Is your motor 5 or 12V?

6

Converting a 5-wire unipolar motor to bipolar yields a motor with double the winding resistance.
Thus the minimum supply voltage is twice the original voltage (ie 10V). With a chopper driver like
the DRV8825 you need another 50% margin for headroom (more is perfectly fine), so 15V or more
supply is needed for this converted motor, and setting the current to the original value of 0.22A
is correct.