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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Sv443 on January 14, 2018, 02:46:29 pm

Title: how to avoid ground loops in battery powered projects?
Post by: Sv443 on January 14, 2018, 02:46:29 pm
Hi, I'm making a bluetooth speaker right now but no matter what I do, I keep running into a really annoying problem. I am using a TP5000 3A li-ion protection board. The 4V output gets amplified to 12V to drive the speaker and to 5V to power the KRC-86b bluetooth module. But if I do that I get really annoying distortion and background noise. I have heard that sensible electronics and audio-electronics sometimes run into this problem too and I wanted to know how professional manufacturers solve this and how I can solve this issue.

Please keep your answers simple, I'm not the best electrician.

Thanks!  ;D
Title: Re: how to avoid ground loops in battery powered projects?
Post by: madires on January 14, 2018, 02:55:02 pm
Could be the boost converters. Do you got a lab PSU to power the amp and the Bluetooth module directly for testing?
Title: Re: how to avoid ground loops in battery powered projects?
Post by: Sv443 on January 14, 2018, 06:33:00 pm
Quote from: madires on January 14, 2018, 02:55:02 pm
Could be the boost converters. Do you got a lab PSU to power the amp and the Bluetooth module directly for testing?

Yes I already tested it with an external PSU and it solved the problems. And I also think its the boost converters but without them I don't know how to do it.
Title: Re: how to avoid ground loops in battery powered projects?
Post by: David Hess on January 15, 2018, 02:14:02 am
Single point grounding to prevent ground loops and RLC decoupling between modules is usually enough to prevent problems.  In extreme cases with audio circuits, I have used currents instead of voltages or instrumentation/difference amplifiers to remove ground noise.
Title: Re: how to avoid ground loops in battery powered projects?
Post by: madires on January 15, 2018, 11:14:18 am
You could try adding LC filters to the outputs of both boost converters, maybe 10 or 22µH and 470µF as a starting point.
Title: Re: how to avoid ground loops in battery powered projects?
Post by: ovnr on January 15, 2018, 11:28:33 am
Have you checked which power rail is the biggest problem? Consider adding linear post-regulators to the boost converters.

If you're adding LC filters like madires suggests, make sure that you're making a properly damped system. A low-ESR inductor paired with a low-ESR capacitor will ring at certain frequencies. Using a higher ESR inductor - or even adding some series resistance - plus a good old aluminium electrolytic will make it easier to avoid any such issues.