Andy I re read your original post and I see the problem it hinges on the word simple. what you want is a mechanical latching relay that resets when the coil is pulsed. Potter & Brumfield s89r series could be mounted with the armature accesable and mechnicaly set by the Filler then reset by the micro after power up. I got this from an old p&b catalogue so it may not be a good # but p&b would be a place to start Terry