I need to plug a micro controller in device which seems to run a PSU with a common VCC and two "grounds"
A common 0V a -3.3V and a -5V. I want to add a 3.3V powered microcontroler (The easy part) and drive a 5V relay using the microcontroller.
I tried to drive the relay using a mosfet but since the relay is 5V powered and as far as I understand there will be a 1.7V Vgs between the -5V and the -3.3V (GND ref for the microcontroller) and this will be enough to switch on the mosfet.
So I thought about this: http://www.circuits.io/circuits/2632
Will this work ?