I'm working on a seemingly simple Arduino project which plays a sound and flashes an LED when provoked by some trigger.

The problem:

When powered by an external power supply, the Arduino continually resets after playing ~1/4 seconds of audio. When powered from USB, it works fine (however the LED, being powered from the external power supply, of course does not work here).

Wiring diagram:

wiring diagram

Parts list:

  • Arduino Pro Mini 5V
  • Adafruit MAX98306 3.7W amplifier
  • Sparkfun FemtoBuck LED Driver
  • 4 Ohm 3W speakers
  • 3W LED

I am using a 9V 1A power supply. Again, when no speakers are connected, the Arduino and LED work as intended. It's only when a speaker is connected that the board resets over and over again. Playing roughly 1/4 of a second of audio and then resetting implies to me that there's insufficient current, however, the problem persists even after using a 2.5A power supply.

Things I have tried:

  • Increasing the power supply to 12V 2.5A
  • Desoldering the LED driver (even with the LED driver removed, the board still resets)
  • Checking continuity and staring at the wiring for long periods of time while scratching my head

Overall, I'm at a loss as to why it would work when powered via USB instead of through my external power supply.

What am I doing wrong? Any insights are greatly appreciated!

  • do you have a few capacitors you can add to the supply lines? 220~1000uF 25V?
    – Wesley Lee
    Commented Apr 18, 2016 at 18:30
  • I do, but I'm not knowledgeable enough about capacitors to understand what that would provide. Can you elaborate?
    – shanet
    Commented Apr 18, 2016 at 18:38
  • I'm having a similar issue and was wondering where you put the 5v regulator in the wiring diagram? Would it go between the external power supply and the arduino? Or just after the arduino?
    – user20740
    Commented May 2, 2016 at 20:57
  • @Josh it's best to ask a new question and reference this question instead of piggybacking off of another question. You'll get more eyeballs that way.
    – shanet
    Commented May 3, 2016 at 8:01

2 Answers 2


Most likely lack of current - lack of current able to be provided by the Mini. The audio is powered from the onboard regulator on the Mini, which has limited current capacity.

If too much current is drawn it will either get too hot and go into thermal shutdown until it cools down enough, or it will drop the output voltage, making things reset and crash.

Power the audio system from an external 5V regulator.

  • But why would the speakers work when the Arduino is powered via USB? The amplifier is still be powered by the Arduino regardless of what the Arduino is powered by.
    – shanet
    Commented Apr 18, 2016 at 18:37
  • Because when powered by USB you're not using the onboard regulator. You're providing 5V directly so the regulator isn't needed.
    – Majenko
    Commented Apr 18, 2016 at 18:41
  • Ah, that clears it all up! Okay, I'm off to get a 5V regulator. Thank you!
    – shanet
    Commented Apr 18, 2016 at 18:43
  • I now have a 5V regulator in the circuit that I picked up from the local electronics supply place today and everything is working wonderfully. Thanks again!
    – shanet
    Commented Apr 19, 2016 at 6:20

your power supply may be faulty. try a another power supply which can supply more current and common the GND of arduino and power suply..it may have internal short circuit or lack of current.

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