Unexpected Digital Input Triggering SOLVED

[salmec]

I want to share with you what drove me crazy for a few days.
I connected a button to a digital input (with a pull-up resistor), and when I connected the Arduino UNO via USB, everything worked fine. The application generates sounds, and I connected a 12V DC power supply to an audio amplifier while also powering the Arduino with 12V DC.

Then, strange things started happening—the digital input would trigger randomly. I even disconnected the wire from the button, and the input would still activate on its own unpredictably. After spending a few days debugging the software, I thought the issue might be with the power supply. I switched the 12V DC power supply to a more powerful one, and everything was fixed!

Apparently, the amplifier was drawing too much current, leaving too little for the Arduino. I hope this helps others too...

Regards

Salmec

[Paul_KD7HB]

@salmec

Then, strange things started happening—the digital input would trigger randomly. I even disconnected the wire from the button, and the input would still activate on its own unpredictably.

But you still had the pull-up resistor connected. The voltage drop on the resistor when the extra current draw suddenly reduced the voltage on the resistor which is identical to what happened when you pressed the button.