Can I send 6 volt pulses to step & dir pin A4988 w Volt Reg?

Hey guys

I smoked an operational amplifier on my Arudino UNO earlier attempting to get my cnc electronics to work.

To cut a long story short the Aruduino still works for the most part, however the digital output pins are now producing pulses of 6 volts (or 12 volts depending on the pin) instead of the 5 volts it should actually produce.

So my question is, Can I still use these pins without damaging my stepper driver (The A4988 with Voltage Regulators)?

Also I was wondering if you knew of a forum thread which did a good job of explaining how to check if stepper drivers still work?



Looks like my abnormal arduino voltage was due to a dodgy mulitmeter.

However I am still uncertain if my boards have fried in the accident which caused the inital problem.

I am still troubleshooting though. and I was wondering if anyone had a wiring diagram for twsting the a4988 driver with voltage regulators, with the motors disconnected as I heard this was a good way of evaluating the damage?

Thanks for reading!


You should test the Arduino to make sure it is not damaged before connecting it to the A4988 stepper motor driver. You might try writing a program to drive each pin low and high to make sure it outputs 0V and 5V. If it does output 6V or more, you should not connect it to A4988 stepper motor driver since they are damaged and might not preform as expected. Also, the maximum input logic voltage for the A4988 is 5.5V.

To test your A4988, you can supply both logic and motor power to the board without a motor connected and see if the voltage on the “ref” pin changes when you turn the potentiometer.

- Jeremy

Hi Jeremy

Thanks for responding

I did something similar to what you described last night, I will check again when I get home from work.

With regards to the second suggestion, can I leave the step and direction pins disconnected ( I am assuming I should if I am just checking current across the pot).


Ok I tested the driver like you described, the vref changes when I turn the pot

What would the next step be from here?


If the voltage on the “ref” pin changes, I do not suspect your A4988 stepper motor driver carrier is damaged. At this point, I would connect the driver according to the minimal wiring diagram on its product page and see if you can get a motor to step; however, I do not recommend connecting the Arduino to the driver unless you have verified that it is also working properly.

- Jeremy

I am not having much luck getting the motors to turn

Should the two ground pins either side of the voltage logic selector be connected together?

Also is there anyway of manually stepping the motor without the use of an arduino?



The GND pins are connected through the board, so you do not need to add an external connection. You could drive the STEP pin high and low manually with a wire or switch, but it might take several cycles to notice if the shaft is moving.

Did you set the current limit of the driver to match the rated coil current of your stepper motor? Could you post pictures of your setup? Could you also post the code you are using?

- Jeremy