I'm using a DRV8871 motor driver to control with PWM a brushed DC motor at 26V, mounted on this shield. The setup is part of a larger system with multiple stepper (controlled via dedicated drivers) and brushed motors (controlled with other drv 8871 but without PWM).
My concern is that the motor shield ties GND and POWER- together. In my setup:
- GND is connected to the power source DGND
- POWER- is connected to 0VMOT
- POWER- and DGND are connected inside the power source
Could this be causing a ground loop? Is it better if I remove GND wire from the shield?
Here’s my schematic, along with my hypothesis:
Schematic whith potential loop highighted DRV8871 shield schematic:
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\$\begingroup\$ My doubt is related to the power source, I don't understand why it has a DGND and a 0VMOT, could you please give more details on that? POWER- could also be connected to DGND if this is the reference ground for +24VDC. Making these connections, did you check for ground loop or some malfunctions by having the system work with some tests? \$\endgroup\$Alinik– Alinik2025年02月06日 11:03:51 +00:00Commented Feb 6 at 11:03
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\$\begingroup\$ Are you saying there is something strange going on with the motors or other circuits? You should post the schematic of the shield rather than rely on links that usually break in time. \$\endgroup\$Andy aka– Andy aka2025年02月06日 11:04:19 +00:00Commented Feb 6 at 11:04
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\$\begingroup\$ From your schematic, in the power suorce DGDN and 0VMOT are connected, so if POWER- and DGND are connected inside the power source all the circuit is at the same ground reference. \$\endgroup\$Alinik– Alinik2025年02月06日 11:49:39 +00:00Commented Feb 6 at 11:49
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\$\begingroup\$ @Alinik, yes, they are connected, Sorry but maybe is not clear to me. does it means that there can't be a ground loop? \$\endgroup\$Luigi– Luigi2025年02月06日 13:14:13 +00:00Commented Feb 6 at 13:14
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\$\begingroup\$ @Luigi If DGND and 0VMOT are connected to each other, it is as if POWER- of the shield is connected to DGND of the power source, basically DGND and 0VMOT is as if they correspond to the same single pin. To confirm this, continuity should be tested with a multimeter between the GND pin and the POWER- pin of the shield: if continuity is present then everything is at the same ground potential. Although in the schematic it looks like there is a closed ground path, there does not have to be a ground "loop". \$\endgroup\$Alinik– Alinik2025年02月06日 13:19:57 +00:00Commented Feb 6 at 13:19
1 Answer 1
A ground loop is an undesirable phenomenon that occurs when multiple paths to ground exist in an electronic circuit or system. These paths form a closed "loop", in which a potential difference between the ground points generates a parasite current that flows through connecting cables or metal structures.
So if there are two different ground references and there is even a small potential difference between them, then a ground loop could be present.
In your case, if DGND and 0VMOT are connected to each other in the power source, you have only one reference to ground potential and it is the same for both the power source and the DRV8871 shield.