[SOLVED] Common ground problem

Apr 27, 2021
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Hi everybody ... this is my first time posting a question on this forum, so I apologize for any technical pitfalls in my questions. I am working on a project in which I want to design a simple dc motor control module (consists basically of two mosfets), that is to be connected later to a processing unit (arduino in my case). My problem is that in order for the mosfets to operate (and work as a switch to conduct electricity to the dc motors), it should have the same ground as the arduino (or else, if the arduino gives a "high" signal, it wouldn't be understood by the mosfet). However, the arduino is connected to some sensors and other modules that are disturbed when they have the same ground with motors.

In order to solve this, I separated the electricity of the motors from that of the processing unit (so the motors work with a separate battery, while the arduino and the other sensors work with another separate battery), and I linked the arduino with the mosfets using optocouplers (pc817). This solved the problem of having common ground, but the system became more complicated.

One of my friends told me later that I didn't need to do this, and that this problem (that of common ground) can be solved easily by just re-routing the circuit in a certain way that separates the physical traces of the digital devices than that of the mosfet and motors.

Someone said that I should use a capacitor across the motor leads. Something like a ceramic capacitor 0.1µF directly across the motor leads. (In case you don't know much about ceramic capacitors.)

Is that right? Or is there another way?
 

jay32267

Glorious
I think that without seeing a schematic of the actual circuit....there's no way to give a definitive answer.

Without knowing all the other components involved...we have no way to know what adding that .1uF cap is going to affect.

...and without knowing the electrical characteristics of the motor....we have no way of knowing how it's going to affect the motor.
 

jay32267

Glorious
I think that without seeing a schematic of the actual circuit....there's no way to give a definitive answer.

Without knowing all the other components involved...we have no way to know what adding that .1uF cap is going to affect.

...and without knowing the electrical characteristics of the motor....we have no way of knowing how it's going to affect the motor.
 

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