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Topic: Nano-A4988-Nema17 all from one 12V P/S - jitter when powered on.. (Read 90 times) previous topic - next topic

FrictionFit

Hi there, Yes, I'm new.

I've connected a nano-A4988-and Nema 17 and written some tests to have two momentary switches (buttons) advance the steppers either forward or backward with either button push.

When I power the Nano via USB from my laptop, everything works peachy.

As soon as I try to use another 5v source (to power the arduino and A4988), the stepper motor does a little freaky rumble spin before settling down and doing as per my program.

In the attached diagram you can see the wiring where I tried to use the 12v input that powers the motor into the Vin (pin 30) on the Nano board.  Freaky rumble.

The other method I tried was to take the 12V power into a rail on the breadboard and take that 12v out to a DC buck converter (with built in LCD to get really very close to 5V) and take its output to a 5V rail on the breadboard and then jump that rail over to power to both the Nano and the A4988.  Freaky rumble.

The third method was to cut up an old mini USB power only cable (black and red wire only, pretty simple) and use the buck converter 5V output to power the Nano via USB.  Freaky rumble.

I then tried to modify the code to set the enable pin on the A4988 to High right in the void setup before the void loop.  No luck, Freaky rumble.

I'm now scratching my head as to what I'm missing.  The only way it doesn't shake and rumble as soon as I put power to the 12V rail, is if the Arduino (and subsequently the A4988) is powered by usb from a computer....

I there a way via code to prevent or pause the A4988 from engaging with the stepper motor at all until the Arduino boots up?  something like a startup sequence?  Am I on the right track?

Ultimately I'd like to have the whole setup run on one physically small single voltage power supply (12V). 


Any assistance would be appreciated.  The forum has got me this far, however my forum search led me to only 1 (crossposted) article where the guy built something cool but didn't really explain how he solved his problem...

I will try to attach a schematic and my code here, it is pretty rudimentary for you all I'm sure.


TIA

groundFungus

What is the coil current of motor driver set at?  What is the current capacity of the power supply?

FrictionFit

Thanks for your response

The stepper power is 12V.  The power supply has plenty, 5A.

After chewing over it on the weekend, I felt like it really was a matter of timing.  The wiring had the 12V power supplied to the buck converter (12V to 5V for Arduino power) AND the VMOT on the A4988 at exactly the same time.  The Arduino and the A4988 didn't have enough time to boot before the motor power was supplied.

To test, I took the 12V supply to the buck converter (down to 5V) and the Arduino first via usb.  Arduino, A4988 (and switches) got the 5V from the Arduino pin 27 and GND.

After a few seconds,  I applied the 12v motor supply power to the A4988.  Bingo, No Freaky Rumble.

Now I'm wondering if there is such thing as a cheap 12 V delay switch that can hold back the 12V for 1 or 2 seconds while the arduino boots.  I'd put it between the 12V power supply and the VMOT on the A4988 but not on the 12V supply to the Arduino usb via the buck converter.

Can this be as simple as a capacitor wired correctly on the 12V line I want delayed?

Sorry, that might be out of arduino territory, but I'm sure people here know the answer.  I'm in Canada if you know a premade 12 V delay switch.

Alternately, is there a way into the A4988 to create an automatic delay on the passing of the 12V from the VMOT in to the actual stepper motor?


Thanks again for your response.

Nek

FrictionFit

Solved.

This is what I did.  I just put a switch on the 12V supply to the VMOT on the A4988 and switched it on after the arduino had fully booted.

Thanks for all the help.

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