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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)
( have a further understanding of Optocoupler working principle and basics=http://www.apogeeweb.net/article/69.html). 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 rerouting the circuit in a certain way that separates the physical traces of the digital devices than that of the mosfet and motors.

I don't know what is the best solution. Can anyone help me with that? Thank you in advance.

Hi Joshua,

Interfacing to inductive power loads can be a dark art. Not only that consideration must be made to transients and back emf problems. You have not included a circuit diagram so it is hard to help you further.

Your best bet is to buy a dedicated driver board to control the motors and you just supply control signals.

To give you an example look at the range which include DRV8838 DRV8835, DRV8833, DRV8832, DRV8801 http://www.hobbytronics.co.uk/motor-con ... tor-driver or https://www.pololu.com/category/11/brus ... or-drivers

There are many many others with different drive specifications. I think the DRV8838 single motor version I used was about £3.50 and the dual motor version was about £5. The above device family have separate power and logic so you can drive, say, a 36V motor directly from an I/O microcontroller pin

Matt

We have designed circuit boards previously with common grounds between the power ground and analogue ground. To aid in keeping the noise out of the analogue keep the two grounds as separate as you can and connect the two together at a single point. We found a single 0R resistor worked well to keep things separated when laying out the circuit.