in brains,
use your sensors for your plazma on, as your input on brains, then do an invert signal, then out to Push Button "Pause".
So when your sensor is off, your pause is on, and whne your plazma is on, your pause if off,
if you want to you can make an "Or" box, after your invert that one of its inputs can be an override from an LED or something, to override the sensor/pause.
scott