I plan on making a version of this circuit to control a 12V PC fan using an ESP32. The ESP32 GPIO pins are 3.3v logic level.
You can ignore the lower part of the circuit in that diagram. That part is stepping down 5.5V to 3.3V because he wants to use only one 5.5V power supply to power both his board and his LED strip. I don't have that problem, my board has its own power supply, and I plan to use a separate 12V wall wart to power the fan via the TIP120
Here are my questions:
- Will the 3.3V logic level at point (1) from my ESP32 board be sufficient to switch the TIP120?
- What is the purpose of the resistor at point (2)?
- Is combining the grounds of the 3.3V and 5.5V sides of the circuit at point (3) intentional, and is that a best practice? If so, why is that done? Should I also do that with my 3.3V/12V circuit?