Canceling Ground loop noise

Thread Starter

Sudarshan Hegde

Joined Dec 12, 2020
12
Hi... Guys.. Actually I was trying to build a Bluetooth speaker, and I bought Bluetooth module(https://www.amazon.in/dp/B07V3WS9XN/ref=cm_sw_r_cp_apa_i_-mp1FbX974D50?_encoding=UTF8&psc=1) and a amplifier . Everything was working except ground loop noise. When I connected seperate battery, there was no noise. But I want to create speaker using single battery. So I created some dc to dc isolator. But that module is not turning on by isolator. I tried everything... So please suggest me any ideas..
Sorry if explanation looked boring
(Included schematic for dc to dc isolator)
 

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Audioguru again

Joined Oct 21, 2019
2,405
The minimum supply for an ordinary old LM5455 or NE555 is 4.5V so your 3.7V (or less when it is running down) is too low.
Your voltage stepup then 5V regulating circuit wastes a lot of battery power.
 

crutschow

Joined Mar 14, 2008
26,032
You cannot drive a transformer with a single-ended signal, as it will saturate the transformer core.
You need to drive the transformer with a push-pull driver through a series capacitor to the transformer to block the DC component.
 

Thread Starter

Sudarshan Hegde

Joined Dec 12, 2020
12
You cannot drive a transformer with a single-ended signal, as it will saturate the transformer core.
You need to drive the transformer with a push-pull driver through a series capacitor to the transformer to block the DC component.
Thank you for replying. Can you give diagram for that...
 

KeithWalker

Joined Jul 10, 2017
1,405
Everything was working except ground loop noise. When I connected seperate battery, there was no noise. But I want to create speaker using single battery.
What type of battery are you using and what is it's output voltage?
Do you have any capacitive decoupling on the power source?
How long and what guage are the wires from the battery to the wireless module and amplifier?
What kind of "ground loop noise" are you getting? Is it power line frequency, digital noise, oscillation or random background noise?
 

Thread Starter

Sudarshan Hegde

Joined Dec 12, 2020
12
What type of battery are you using and what is it's output voltage?
Do you have any capacitive decoupling on the power source?
How long and what guage are the wires from the battery to the wireless module and amplifier?
What kind of "ground loop noise" are you getting? Is it power line frequency, digital noise, oscillation or random background noise?
I used 3.7v li-ion battery. No capacitive decoupling on power source. I hope it's 'power line frequency', cause when I used seperate power sources there was no noise.....
 

KeithWalker

Joined Jul 10, 2017
1,405
How long and what guage are the wires from the battery to the wireless module and amplifier?
This is important because the length and guage of the wires from the battery to the modules can affect their performance.
A capacitor across the supply voltage at the input of each module can eliminate most interference between them. I would suggest a 47uF electrolytic for each module.
Both the modules you are using are designed for a 5V supply, so performance will be marginal at the best as the Li-ion cell voltage drops from 4V to 3V.
 

Thread Starter

Sudarshan Hegde

Joined Dec 12, 2020
12
How long and what guage are the wires from the battery to the wireless module and amplifier?
This is important because the length and guage of the wires from the battery to the modules can affect their performance.
A capacitor across the supply voltage at the input of each module can eliminate most interference between them. I would suggest a 47uF electrolytic for each module.
Both the modules you are using are designed for a 5V supply, so performance will be marginal at the best as the Li-ion cell voltage drops from 4V to 3V.
I used 29 gauge copper wire, and it is around 10 cm long.
Thank you so much for replying
 

KeithWalker

Joined Jul 10, 2017
1,405
29 guage wire is rather thin for powering an audio amplifier but with such a low supply voltage, there will not be much audio power out so the supply current will be low. I think 10cm of 29 guage will probably be OK. The decoupling capacitors are very necessary to keep things stable.
 
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