A4988 spins my motor when turning on arduino uno

Hi all,
does anobody know why A4988 spins few steps when I turn on Arduino Uno just by connecting USB to PC ? Other single steppers units does not do it.

Which code did you upload to your Arduino Uno?

GRBL

Might be that some pins are strobing during power on. You could try to place a delay circuit on the enable pin. Use a resistor and capacitor from +5V to ground. Connect the middle pin to enable pin. While the circuit is turned on, the capacitor charges, at some point the enable pin goes high and the circuit can be used. Play around with values for capacitor and resistor.

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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

Could also be the boot loader, it pulses the LED line 3 time or so, if thats connected to a step pin. and enables set, it will move.

Edited 1 time(s). Last edit at 11/16/2015 04:45AM by Dust.

Thanks for answer, is there any existing schema with proper values of this resistor and capacitors ?