How Do I deal with common ground

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1

Hi SparkFun Community,

I’m A total noob when working with circuits, and I need guidance on proper grounding practices with the TB6612FNG motor driver.

My Complete System:

Multiple ESP32 microcontrollers
Multiple ESP-EYE camera modules
SparkFun TB6612FNG motor drivers
DC motors
LEDs
Servo motors
MEMS microphones
MOSFET drivers
Temperature & humidity sensors
Two separate 5V power supplies (one for VCC/logic components, one for VM/motors)

The Challenge:

The TB6612FNG hookup guide states that VCC and VM grounds are common on the board. However, my professor strongly advised against connecting the grounds of both power supplies together in a system like this, citing:

Motor noise interference with sensitive analog components (MEMS mics, sensors)
Potential disruption to camera modules and multiple microcontrollers
Ground loops and noise coupling between high-current motor circuits and low-noise digital/analog circuits

Specific Questions:

  1. In a multi-microcontroller system with sensitive analog components, what’s the recommended approach for using the TB6612FNG with separate power supplies?
  2. Can the TB6612FNG function properly with isolated grounds, or does it require a common ground reference?
  3. Are there hardware modifications or external isolation techniques that would work?
  4. Should I consider alternative motor driver solutions that better support ground isolation?
  5. What are the best practices for power distribution and grounding in mixed analog/digital systems with motor control?

I want to maintain signal integrity across all components while following proper EMI/noise reduction practices. Any insights on system-level grounding strategy would be invaluable!

Thanks for your expertise!

2

That is almost always the case with small motor driver modules, so just leave those grounds connected.

There are many ways to deal with motor noise, such as proper shielding if necessary, proper lead dressing and placement (keep signal and power/motor leads well separated), use power supply decoupling techniques, etc. With those precautions motor noise is rarely a problem. Useful tutorial from Pololu.

Your professor could be emphasizing their personally favorite approach, or you missed the rest of the lesson. I suspect the latter.

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3

I think OP’s instincts and reasoning are leading in the right direction.

This sounds like a good opportunity for some experimentation. I’d start by building the device with fewer ground isolation provisions like @jremington suggests and see how it goes. Isolation beyond adequate isn’t needed.

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4

For severe cases, like electrically noisy industrial installations, motor drivers are available with optoisolated control inputs. That allows complete separation of ground connections between sensor/control circuitry and the motor system.

5

Thank you for your insight and the Pololu tutorial link!

You’re absolutely right - I’m a CS major working with circuits for the first time, so I’m still learning the electrical engineering fundamentals. I probably did miss some nuances in my professor’s explanation about grounding practices.

I’ll study the Pololu guide on motor noise mitigation and see what changes.

Really appreciate the guidance

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6

Thanks for the encouragement!
I think I’ll start with the simpler setup (common grounds as the TB6612FNG is designed for) and implement the basic noise mitigation techniques from the Pololu guide.

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