the cathodes are attached to the horizontal layers (green wires in the image below – bottom right – shown passing through NPN transistors). The Arduino Mega 2560 R3 is positioned on a ...

If you want to control it from a 3.3 V MCU that can’t handle the high-side voltage on its pins, you can add a NPN transistor section as shown – this inverts the logic, making it into a more ...