Do we need to give isolation power input to the stm32 board

[Karthik DM]

Hello all,

I'm currently working on a BLDC motor controller. Currently, I'm facing some issues with the STM32 Nucleo board. when I connect MCU ground with my inverter ground whole system is not working. if I remove the ground system is working.

Initially, I thought I need to give isolation power to MCU. But I haven't got any reference documents for that.

Can anyone please help me to solve this??

[TDK]

It doesn't need isolated power, just needs a stable power supply. If removing ground causes it to work, that suggests it doesn't need the ground you're attaching. Make sure you're not introducing a ground loop, or connecting grounds with different potentials.

[Karthik DM]

Hello

Thanks for your valuable suggestions.

Currently, my power board is powered with 48V DC and My MCU is powered by USB from my laptop.

When I connected MCU ground to Powerboard ground. the system is stopping.

I need to connect both the ground to get better results. But its not working when I connect grounds.

[TDK]

Is your power supply stable? Motors generate significant electrical noise. Monitor your power rail. Debug the code to find out what "not working" means in particular. Don't introduce ground loops, especially in the presence of electromagnetic noise.

[Karthik DM]

Hello Sir,

My power supply is much stable.

I will check as per your valuable suggestions.

But there is no requirement of isolated ground in stm32 right sir ?

[TDK]

There is no requirement for an isolated power supply, but it is a possible solution if your application cannot otherwise keep the supply stable.

[Karthik DM]

Okey Thank You so much your response

[magene]

You might consider sketching out the overall grounding scheme. If the 48VDC power supply is plugged into the wall with a 3 prong plug and so is the computer providing the USB then more than likely there's a ground connection in that path. When you connect the USB to your MCU, that might be another ground connection creating a ground loop like @TDK​  mentioned. I'm not sure what your "power board" is and how it's grounded but it might be the motor controller and that's another possible ground loop. It's pretty typical to make sure you have a single point ground. All the grounds in your system should radiate out from that point. In this case, you might want to make either your 48VDC supply the single point or maybe the power board. Other options to consider are a USB isolator and running the laptop off its battery, unplugged from the wall. It is kind of a pain but this isn't a wildly unusual problem.