/diy/ - Do It Yourself

>>2789400
Good explanation.
You have to develop a “field” between the gate and either the source or drain on the 6v side.
The easiest way to do that is in the circuit shown.
The “switch” part between the gate and source on the 12v side has to share either the gate or the source. There are other ways to turn on the gate, perhaps light, or if you could get enough electrons on the gate with a single charged wire.

Imagine an equivalent relay that only has three pins? How would that work? Examine picrel.