I try to solar charge a supercapacitor C1. When it's fully charged, I use a Zener diode D2 to the gate of an logic MOSFET M1, which then opens the circuit to power an ESP32/Arduino (using an MCP 1700-3302E converter from 3-5 V to constant 3.3 V. I think I need another part to use the full 5V of the capacitor). Once the MOSFET turned on, however, it says on. I can't use a pull down resistor, because I need the capacitors energy down to 0.5 V.
So. Is there a way to pull the gate to gnd, only once the voltage is below any threshold?
I use the zener, because I don't want to power any electronics unless the voltage of 4.7V is reached. But I need to find a way to pull the M1 mosfet back to GND, once the voltage drops below say 0.9V.
Basically I want a MOSFET that turns on at 4.7 V and turns off below 0.5 V.