Adjustable low supply voltage shut off circuit

Using an op amp and a zener diode as a relatively stable reference voltage, you can use the changing voltage of the supply and a voltage divider to shut off a load when the supply voltage gets low enough. Using a trimpot as the voltage divider allows you to easily adjust the point at which the load is turned off.

[@Gary-vo9rm]

One of the mistakes I used to make (just learning), was not using resistance on the low side of the pot and would fry them when "turning down." I'm slow. Fried a *lot* of pots :-)

[@Electronzap]

Yeah. The inputs of op amps don't need current, so you can attach both ends of the trimpot to the supply voltage, and the wiper to the op amp input. But if you want to set a resistance with the wiper, then you definitely need to make sure there's enough resistance elsewhere in the circuit for when you set the wiper towards o ohms.