Driving a 12V 28BYJ-48 Stepper With the A4988 Stepstick

Table of Contents:
Step 1: Parts
Step 2: Setting Up the Motor, CNC Shield, and UNO
Step 3: Writing Code and Running the Motor
Full Disclosure: One A4988 stepper driver was destroyed with reverse polarity during the making of this instructable.
Warning! 12VDC being back fed into the UNO from the CNC shield and then from the UNO to your computer could potentially destroy your personal computer. This is why I am unplugging the USB cord from your PC before providing 12VDC to the CNC shield.
Facts:
The 28BYJ-48 is not broken out on it’s header connector correctly (ignoring the red wire entirely) to be connected one for one to an A4988 stepstick driver. In short, the pink and yellow wires need to be crossed over.The spec. sheet states that an A4988 needs > 8VDC power supply for your motor, i.e. you may not be able to run a 5VDC power supply for driving 5V 28BYJ-48 motors.You do not need to disconnect the 28BYJ-48 red wire to run it in bipolar stepper mode. I have done it both ways and have seen no difference, although I have no quantitative data to back up this assertion. However, visually, stepwise, and to the touch (heatwise) I have noticed no difference in my limited trial.You need to dial the potentiometer back on the a4988 to restrict it’s current flow. I have mine set to 0.10V. Although, it didn’t blow the A4988 or 12V stepper even when I had the ‘pot’ originally set at 0.50-0.60V, this high pot reading could however prove dangerous if run for too long at this setting, burning your 28BYJ-48 motor, A4988 stepstick, or place of residence up.Disclaimer: I am not an electrical engineer and my ‘facts’ should be taken as such.
Not needing to disconnect the 28BYJ-48 red wire to run it in bipolar stepper mode, is my opinion (based on my limited trial), and thus should be taken with a grain of salt. Many, claim that you need to both internally cut the circuit track that connects both poles’ common line together, and then to disconnect the red wire entirely. Needing to dial the potentiometer back on the A4988 to restrict it’s current flow is definitely a fact. However, having mine set to 0.10V, is merely my opinion. You should consult the datasheets and use their values and formulas to set this value properly. “

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