I'm working with an Arduino Giga, and I have it set up to run on 12V through the VIN (though my main power is 36V, and I am using a buck converter to bring this down to 12V). There are times that I also need plug the Giga in to the USB-C so that I can use the Serial monitor while the larger system is running (it has both the 12V VIN and USB-C connected, and I have been told that this is fine for Gigas, but please correct me if I am wrong). I have a bad habit of forgetting to unplug the Giga from the USB before turning the power off in my system, and I don't think that this is very good for the Giga because it starts trying to power everything.
What I am looking at doing is creating a power disconnect on the USB. I found some USB-C power split breakout modules, so I was thinking that I would wire them up to connect the data+, data-, and GND together, then place a FQP27P06 MOSFET on the 5V VCC. The idea is that the Giga won't recognize that there is a computer attached until the 5V power is connected, but I don't know enough about how USB communication works to know if this is how things actually work.
My plan is to use:
- the 5V from the USB-C to pull the MOSFET gate HIGH (through a 10kΩ pull-up resistor)
- connect the MOSFET gate pin to a 2N4401 transistor collector pin (through a 270Ω resistor)
- connect the 2N4401 base pin to the 36V (through a 12kΩ resistor)
- connect the 2N4401 base pin to GND (through a 100kΩ pull-down resistor)
- connect the USB-C from my computer to the MOSFET source pin
- connect the USB-C to the Giga to the MOSFET drain pin
Basically, it's high-side switching: the 36V turns the 2N4401 on, which turns the MOSFET on and allows the USB-C power to connect to the Giga. Then, when the 36V turns off, the 2N4401 loses power and the base pin goes LOW, and the 5V from the USB-C coming from the computer pulls the MOSFET gate pin HIGH and cuts the power off.
Is this a usable design? Am I missing anything?
In case the arts and craft version helps to explain what I am talking about:
