I've connected eight 8x8 leds matrices to an Arduino, to display a scrolling banner.
When I developed it on an Arduino Leonardo powered by USB, everything worked fine.
When I moved the solution to an Arduino Pro Mini, I tried to use the onboard voltage regulator (using the RAW pin) but it only worked half of the time (the other half of the time, I only had 2V on the VCC pin of the Arduino).
Even when it was working, the Arduino was very hot after a few seconds, so I assumed the leds required too much power for the onboard regulator, and I moved to a breadboard power supply (see picture).
That's where things start being confuse :
- If I keep the power supply switch on and plug/unplug the power-brick to the main, it works flawlessly and I got 4.8V on the Arduino's VCC pin
- But whenever I try to use the power switch on the power supply, the leds turn on but the Arduino doesn't do anything and its VCC pin is about 2.4V
I would like to know what I'm doing wrong, and how to prevent this kind of failure to happen.
PS: The power brick is ratted for 12V 1.5A; There are 512 leds but they are driven by eight MAX7219 and AFAIU only 64 of them can be lit at the same time