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I'm trying to power up a circuit that consists of an Arduino Nano, 3x 3W stereo audio amplifiers (PAM8403), an audio player module and 20x RGB LEDs. The power source is a lithium battery 3.7V 500mAh. The circuit works perfectly from any USB power bank or USB 2.0 computer port (500mA) plugged directly into the Arduino USB socket, but it doesn't work properly with the step up circuit I chose.

The system only crashes when the volume is louder, so I can assume it's a current issue. The step up DC/DC converter I'm using is the CE8301A. Below is the circuit: enter image description here

Then the Vout line passes through the audio amps first to then reach the Arduino 5V pin and all the rest.

Now I'm considering three options: 1) Change the values of some components. 2) Try a higher capacity battery. 3) Try another step up such as the ME2149.

What would be the best solution? And if the component values can be changed to allow more current to flow, which ones should that be?

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    \$\begingroup\$ 'mA' and 'mAh' are not the same unit. Do you know what your lithium cell's rated peak output current is, rather than its capacity? \$\endgroup\$
    – brhans
    Commented Apr 1, 2019 at 13:10
  • \$\begingroup\$ no, the seller didn't provide this information. It's a 602535 500mAh Lithium polymer battery model DZ00912. \$\endgroup\$
    – Emerson
    Commented Apr 1, 2019 at 13:15
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    \$\begingroup\$ now I tested with a similar battery of 800mAh and the same happens. I understand mA and mAh are not the same unit but I thought a higher capacity battery could have a higher peak output current. \$\endgroup\$
    – Emerson
    Commented Apr 1, 2019 at 13:22
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    \$\begingroup\$ @Chu you're not wrong, a higher capacity could have a higher peak output current, but it also could have a lower peak output current. It really depends on the battery. \$\endgroup\$ Commented Apr 1, 2019 at 13:43
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    \$\begingroup\$ If the battery voltage is not dropping then your problem is with the regulator. Multimeter readings are unreliable with rapidly changing voltages, but if it's hardly changing at all under load, chances are the regulator isn't keeping up. \$\endgroup\$ Commented Apr 1, 2019 at 13:57

2 Answers 2

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If the device crashes when you turn up the volume there is probably an issue with the supply voltage to the micro-controller.

At max you will draw at least 1.8 amp at the 5 V side (the USB 2.0 spec is 500 mA, but often this is exceeded in actual implementations), this comes from the 3x 3 watt you can deliver to the speaker, not including leds (0.2-0.6A if driven at 10mA for each colour). Implying an even higher draw on the 3.7 volt side. The current draw will probably cause a decrease of the voltage on both the 5 volt and 3.7 volt side depending on the C rating of the battery, unfortunately this is not given for the battery, but I found a similar battery and it has a discharge rate of maximum 2C this is equivalent of 1 Amp (2*capacity) draw maximum.

There might also be too little decoupling of the Arduino, remember that the 5V pin bypasses the on board regulator and goes straight to the chip. Your 5V rail is probably also coupled to the same rail as the speaker and the speaker will create noise on your power rail.

Try adding more caps near the Arduino to keep it from getting brownouts, you might also want to get a multi cell LiPo battery and regulate down the voltage in stead of boosting it.

When powered from the 5V on the USB the power will go trough the on board regulator and the chip will probably not experience brownouts. In addition the USB you are using is able to supply more power that the USB 2.0 spec so do not expect this to work on any USB plug.

Probing the power rails with an oscilloscope will probably help you get to the source quickly as the multi-meter is too slow to detect the spikes and drops in voltage.

Also have you done a power calculation on your system? I will presume that you will run out of battery pretty quickly if you are playing music and blinking LEDs with the 500 mAh capacity battery.

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    \$\begingroup\$ this is very helpful! thank you. \$\endgroup\$
    – Emerson
    Commented Apr 1, 2019 at 15:36
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PAM8403 is 2x3W so 1.200mA, not like mentioned above 3x3W. Instead of using this: CE8301A, you should probably use: HX3608, AP2007SPER or smth. like this: MST9225BKP, SE3608, TPS61085DGKR, ME2159AM6G...

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