After this tedious step, he designed a PCB that hosts an Arduino Nano to accept input, two MCP23017 GPIO expanders to give it enough outputs, and CD4066BE CMOS switches to trigger the connections.

LaserControl 🔴 — Arduino 12V Laser PWM Controller A professional single‐file Arduino sketch to safely drive and dim a 12 V laser module using PWM, a MOSFET driver, a potentiometer and a toggle button ...