Author Topic: Question About Grounding  (Read 1330 times)

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Offline damanfbTopic starter

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Question About Grounding
« on: August 27, 2010, 04:04:48 PM »
Hello,  I am working on a mechatronics project at my university and have a question about connecting common grounds...

My setup is a +12V AC/DC converter, a +36V AC/DC converter.  I have the +12V adapter running to three DC to PWM motor controllers and a bipolar stepper motor driver.  I have the +36V adapter running to two bipolar stepper motor drivers.  I understand that I need to connect their ground for the power circuit to work correctly.

The output of the PIC is being sent as a digital signal to each of the motor controllers.  I have them running from the output pins and the ground of the signal to the ground on the PIC'S breadboard.  Do I need to connect the onboard ground to the ground of the power supply or not?? I was thinking I don't because the adapter which powers the PIC is connected to the same power strip as the AC/DC converters so the power supply is grounded. 

In short, do I connect the digital logic ground to the power supply ground?

Another question I have, is the power supplies have a +V, COM, and Ground.  I have the +V and COM running to the controllers.  Do I need to connect the COM to the Ground on the supply or should they be connected internally?

Any help is greatly appreciated.  I'm fairly new to this area and wanted to ensure I didn't burn out my lab's PIC.
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Offline madsci1016

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Re: Question About Grounding
« Reply #1 on: August 27, 2010, 04:17:14 PM »
For starters, the 'Ground' on your power supply is most likely an Earth ground. This is different from the ground (0V) in your DC circuit.

Next, just because the power supplies are connected to the same AC power strip does not mean their DC grounds are connected together.

Everything your PIC is connected to, needs to share the same ground connection as the PIC itself. So yes, the DC grounds need to be connected together.

Here is a good description of the different types of grounds in the world.
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Offline Admin

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Re: Question About Grounding
« Reply #2 on: August 28, 2010, 08:13:42 PM »
In addition to making sure all grounds are connected, make sure the ground wires for high current stuff go straight to the power source ie doesn't pass through the ground of a sensitive microcontroller first.
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