Maker Pro
Maker Pro

MP3 module resets at low battery voltage

akruby

Aug 11, 2021
3
Joined
Aug 11, 2021
Messages
3
Hello,
I have made a MP3 player by putting together few modules namely,
a MP3 module which plays from SD card with onboard amplifier
https://robu.in/product/gpd2846a-tf-card-mp3-decoder-board-2w-amplifier-module/
a 18650 battery with charging and protection module
https://robu.in/product/tp4056-1a-lipo-battery-charging-board-micro-usb-with-current-protection/
a voltage boost module to boost the battery voltage to 5 volts
https://robu.in/product/mt3608-2a-max-dc-dc-step-power-module-booster-power-module/
and a speaker - 8ohms 5Watt.

As per the MP3 module spec, it has a 2w amplifier.

The mp3 player works fine for moderate volume when the charge in battery is high (above 3 volts).
If the battery voltage becomes 3 volts, it works for only very low volumes. Increasing the volume creates a trrrrrrr sound in speaker and the module resets (this goes in a loop unless you lower the sound further).

I have few questions :
1. When the battery voltage is above 3 volts, its mostly usable. However, cannot reach max volume. The same problem happens (speaker chatter and module reset).
2. when the battery voltage goes to 3 volts and below, you should use it at very low volumes.

What is the problem here? which component should I try to replace or add ?
I have suspicions on the boost circuit. But I tried to check the output voltage of the circuit with Multimeter (unfortunately I don't have a scope) and its voltage remains constant (5v) when the speaker chatter happens and the mp3 module resets.

Thanks.
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
12,774
Joined
Nov 17, 2011
Messages
12,774
Try adding a 1000 µF electrolytic capacitor between "+ out" and "- out" of the step-up converter. The converter is possibly not suitable for the peak current the amplifier can draw when playing music.
 

bertus

Moderator
Nov 8, 2019
2,733
Joined
Nov 8, 2019
Messages
2,733
Hello,

When the battery voltage is dropping, more current will be drawn from the battery to maintain the output voltage.
The mentioned MP3 module seems to use 600 mA max at 5 Volts.
At a battery voltage of 3 Volts, there will be a current drawn from the battery of (5/3)/0.93 times 600 mA = 1.075 A.
It can well be that the protection of 1 A of the charging module is kicking in.
The 5 is the output voltage, the 3 is the battery voltage, the 0.93 is the efficiency factor of the converter.

Bertus
 

akruby

Aug 11, 2021
3
Joined
Aug 11, 2021
Messages
3
Hello guys,
Thanks much for your insights and suggestions.
As Bertus pointed out, it goes above the rated output voltage of the protection module, this explains why the module might reset. As I can see here, this can occur very fast and hence only a scope will capture that.
Also, answer given by Bertus explains why it might fail at even full battery charge at high volumes (drawing momentary current over 1A) - correct me if I am wrong.
And I hope this should not happen if I connect it directly to the battery (without protection circuit) since the boost circuit can source 2A maximum current (I have no idea how fast the 2A can be sourced and is it well within the speaker driver requirement).
I will try connecting the 1000uf capacitor across the boost module output.

Few more questions popped in my head.
1. Is the speaker I am using okay for that module? I mean, when I see the datasheet of the 8002 amplifier as mentioned in the module, it says it can output around 1.8W at 5volts if the driver impedance is 8ohms. The speaker I am using is a 8ohms 5W speaker.
2. As the module is rated for 600mA, might it draw more than that momentarily? like say, at 4V battery voltage, as per the formula given in post #3, (5/4)/0.93*600 ~ 800mA - which is well within the limits of the protection module, I am guess, the harmonics in the music might draw more than 800mA momentarily ?

Thanks again for your answers.
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
12,774
Joined
Nov 17, 2011
Messages
12,774
The speaker I am using is a 8ohms 5W speaker.
This means the speaker tolerates uo to 5 W input power. As you supply ~ 1.8 W only this is completely o.k.
the harmonics in the music might draw more than 800mA momentarily ?
Definitely, that' where the additional capacitor may help.
 

akruby

Aug 11, 2021
3
Joined
Aug 11, 2021
Messages
3
Hi Harald,

Thanks very much for your answers.
I will try to add the capacitor and try it and come back.

Thanks.
 
Top