Without getting involved with any electronics ... if the shed is dark inside save the 'heat' light, just use a light that comes on at night. You know, with a photo sensor. You can buy just the sensor at the big home stores pretty cheap. Mount the sensor on the inside of the shed and hook it to a light outside the shed. When the shed goes dark, ie the 'heat light' burns out, the outside light comes on. I know it sounds kinda stupid but hey, it's easy and cheap. If the shed is not completely dark, aim the sensor at the heat light and adjust the sensitivity way down ... all the ones I've seen can be easily adjusted.