i have been using a D20 Add a motor as my pop door opener for 3 years and love it. My issue was that my coop is not visible from my house and I wanted to be able to visually "see" the the door was opening/closing as scheduled. The digital timer I use for the door has two outlets. I made a simple light fixture from treated 2x4 lumber and a 7 watt night light bulb. Mounted it on a fence that was visible from my house and ran electric cable to the other outlet on the timer. Now when the timer goes to "on" the light also is on and I can see that the door is operating without having to go the the coop. Since the D20 needs on and off cycles I just adjusted the timers off to a few hours past on so I have a 3 hour window to check.