Universal (ish) Arduino grbl opto-coupler interface also works with logic-level pwm In adding an alternative cutter drive motor (‘spindle’) to an existing cnc machine, an electrically isolated pwm to ...

There’s extensive documentation, GRBL settings, and more pictures in their GitHub repo, too – in case you have a similar CNC and would like to learn about upgrading its controller board!

The machine uses a ‘grbl’ controller, which has an Arduino-based circuit that includes multiple outputs, including a powerful 24V pwm signal that is generally used to drive a 60-80W spindle motor.