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9V battery and LM7805 power a audio AMP failled? Answered

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I use a 9V battery to pass power through a LM7805 to an arduino pro mini,a MP3 module,it works fine.later i am not satisfied with the low voice of the speaker,then i added an Amplifier module.the AMP module is a PAM8403-5V(could be USB powered),but the speaker produce weird sound.  it seemed the PWR was not enough,so i added an extra 5V supply to the PAM8403 module,this time it sounds fine.

But i don't wnat to use two PWR sounces to power them.cause it will be bulky,is the 9v battery OK to power them all?or maybe i should use two LM7805s,one for arduino and MP3 module,and another for the PAM8403 module.

The pic attached is the working wiring of the project

Please help me with this,Thanks.



4 Replies

-max-Best Answer (author)2015-12-15

Use will need something better than the sucky 9V battery. It has too much internal resistance, and the voltage will sag as you pull power from it. It would be like expecting a bike to haul a truckload of firewood up a hill!

a 7805 is a linear regulator. It will only further reduce the power, and the voltage that is dropped across it is straight up wasted. Use instead a small lithium battery, like 2 or 3 CR123As in series, and then use a 5V buck switching regulator for better battery life. You could just hack any old 5V car phone charger.

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Yonatan24 (author)2015-12-13

The 9V battery might not be supplying enough amps = You need a bigger battery, Or you can use a power supply

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rickharris (author)2015-12-12


this gets posted almost weekly.

The above data sheet will explain why your seeing this problem.

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Downunder35m (author)2015-12-12

Similar questions comes up almost weekly, so the short answer:
Do not use 9V batteries if you need power - period.
If you wan to know the details search some of the many other 9V battery threads.

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