birdhouse:
The Mosfets and relays need a voltage in the end circuit though right? If I can add voltage to the end circuit to make it work I may be able to use these.
What "end circuit"? How would any circuit work without a voltage applied to it?
Relays are basically mechanical switches, operated electronically.
MOSFETs have a minimum gate voltage before they start conducting; I don't know what happens if the drain-source voltage is lower than the gate-source voltage.
Optocouplers have a minimum voltage drop over the phototransistor, typically about 0.7V. Any voltage lower than that on the switched side and you won't have any current, not matter how bright you make the LED side. See data sheet for details.