When I wake up thinking about it. Look for any opening to sneak away and tinker. Lose track of time. And can't turn it off to get to sleep.
Whenever you catch even the faintest scent of that kind of obsession, start tracking it down. Start testing and figuring out what's calling you there.
Many times it will just fade away like the glare from the sun on a shiny object, but occasionally you'll stumble onto a door leading you ever closer to your passion.