[K.CLONE-Motor Driver]

This is an Allegro A4988 breakout board for Sanguinololu. It can be snapped apart at the score in case of Allegro failure, and replaced with another or a Pololu. Snap all 4 apart and get a pin-compatible clones for use on boards like RAMPS or Gen7.

Now this is not for the iron wielding solderer. All parts are SMT, and somewhat small - there are some 0402 sized packages. Not to mention the Allegro's thermal pad - a solder pad on the bottom of the chip - can't be soldered without an iron of magic.

Adjusting and testing the current

You change the current to the motor by adjusting the trimpot. Set the trimpot to minimum to start with, by turning the trimpot fully anti-clockwise. Turn clockwise until the motors are not skipping steps at your target speed and load.

There is a test point for VREF on the Pololu but it is missing on the Stepstick. Since it is just the wiper of the pot you can measure it there and it is easier as it is a bigger target. I hold the positive meter probe on the shaft of a metal screwdriver so I can see the value while I am turning the pot. Put the negative probe on a ground pin.

To calculate the current, A = VREF / (8 * RS). For a standard stepstick, RS is the rating of the Sense Resistor = 0.2ohm. So A = VREF / 1.6

To calculate the VREF for a target current, VREF = A * 8 * RS , or A * 1.6 . So, if you wanted 0.8A, VREF = 0.8 * 1.6 = 1.28V

KCLONE-stick.pdf

KCLONE-stick-sch.pdf