No you dont set off your own traps....only mobs set them off within a certain proximity.
Think each trap has 10 uses before its destroyed.....allthough you do have to reset the trap after it has gone off.
Its definetley needed because as the game goes on, the amount of warning time before the hounds strike becomes only a few seconds.....and they turn up in packs of 10+.....and they will destroy you in seconds if you arent prepared.
Thanks, good to know. Is there a certain time that the hounds start spawning (e.g. from day 10 or something)?
Haven't had a chance to play it much so haven't made it past 7 days I think