looking for a timer to open and close a circuit
All timers act like switches, that open and close the circuit based on time.  The voltage rating is typically based on the maximum voltage that can be switched, not the voltage that must be  switched.

If you're looking at timers that plug into a receptacle, those are designed to turn lamps and such on/off.  That's not the type of timer you want.

You'll want a device that separates the power circuit, from the circuit being controlled.