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Grounding rules with shared power between Motor S
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Grounding rules with shared power between Motor S

by creatify on Fri Feb 12, 2021 5:54 pm

Hello all, first post here. Considering the attached circuit diagram, will I experience any issues with powering the motor shield and arduino in this manner from the separate voltage bucks — specifically, when developing on the arduino when it is be powered by USB and the barrel jack is disconnected on the arduino, but the motor and LEDs are are powered by the 12V supply? I want to avoid pushing 12V through the Arduino to power the stepper from the VCC partly because I want to add a fuse to the motor power line in the event the motor stalls.

Also, is it true that I only need to ground the LED strip to the Arudino when the arduino is powered by USB?

I'm open to any suggestions on improving this circuit too as I'm not an electrical engineer, thank you!

Screen Shot 2021-02-12 at 1.45.57 PM.png
Screen Shot 2021-02-12 at 1.45.57 PM.png (61.03 KiB) Viewed 92 times

creatify
 
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Re: Grounding rules with shared power between Motor S

by adafruit_support_bill on Fri Feb 12, 2021 7:20 pm

I want to avoid pushing 12V through the Arduino to power the stepper from the VCC

To separate the motor power from the Arduino power you need to remove the VIN jumper from the shield.

Also, is it true that I only need to ground the LED strip to the Arudino when the arduino is powered by USB?

No. that is not true at all. You ALWAYS need to have a common ground since that is also your signal reference. Your diagram does not show it, but you should have a ground wire running directly from the first pixel of your LED strip to the ground pin of the Arduino.

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Re: Grounding rules with shared power between Motor S

by creatify on Fri Feb 12, 2021 7:48 pm

Thank you for the info! Regarding your response:

"No. that is not true at all. You ALWAYS need to have a common ground since that is also your signal reference...."

When the arduino and components are only running on the main 12V power supply through the buck convertors, are these correct to say: The reason I need to also ground the LED to the arduino in this case is because the signal reference doesn't travel through the voltage buck (which does ultimately share a common ground with the arduino). The signal reference has to make its way back to the arduino through a pin connection.

With my limited electrical knowledge, I struggle to fully understand the path signal references take through a ground line.

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Re: Grounding rules with shared power between Motor S

by adafruit_support_bill on Fri Feb 12, 2021 7:56 pm

are these correct to say: The reason I need to also ground the LED to the arduino in this case is because the signal reference doesn't travel through the voltage buck (which does ultimately share a common ground with the arduino).


Without a direct connection to the Arduino, the signal reference would travel through the buck converters from the Arduino. But that is a noisy path - not a good thing for a signal reference. You want to have a direct connection so that you have a clean stable ground reference for your LED control signals.

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Re: Grounding rules with shared power between Motor S

by creatify on Fri Feb 12, 2021 8:22 pm

Ahhhhh, I see, thank you!

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