Many european apartment houses have stairway lighting that is on around dawn and dusk, but at other times you push a button for about 10 minutes of light. The t

Many european apartment houses have stairway lighting that is on around dawn and dusk, but at other times you push a button for about 10 minutes of light. The timing of these things is not static but follows the sun, and older such equipment was mechanical and used what I imagine was simply a sinusoidally shaped gear. I used to manage a small apartment block in Stockholm and remember setting latitude and day-of-year into ours to get the timing to agree with the sun, and to stay there. Here's a photo of a similar device: http://www.aew-electrical.co.uk/wp-content/uploads/2016/08/electro-mechanical.jpg http://www.aew-electrical.co.uk/wp-content/uploads/2016/08/e...