5 and 12 volt alternating wire

i have a wire that alternates from 5v to 12v and i need it to trigger a relay only when its supplying 12v. the relay will not stay energized when its at 5v nor do i want the relay to energize when its at 5v. id like the relay to only be activated if the trigger wire is above 10v. is there something that i can put inline with the relays trigger wire and only have current flow when is over 10v and stop any kind of current when its bellow 10v?

You could use an op amp circuit that is set up as a comparator. You'll need to transistorize the output in order for most op amps to drive a relay. It's a pretty basic circuit, power the chip, provide the min reference voltage on one input, and your trigger voltage on the other input. When the trigger input is higher then the reference voltage the output will turn on.Kevin Pierson