Automatic light controller looks at sunset time

If you use standard automatic light controller then you know that it is mechanical clock based switch or electronic with ambient light detector. Mechanical one require regular time adjusting since sunset time variates during year. Second one would be OK – it senses darkness with LDR and then turns on the lights. But things happen, LDR may get covered with objects or simply dark clouds my trigger the lights. Anyway there is another solution – smart clock that keeps track of sunset times.


Paulo decided to build lighting timer using sunset and sunrise time calculating algorithm. So lights are turned on time no matter what season is currently on. Additionally Arduino based devices is equipped with 7 segment display, couple push buttons for setting time, battery backed RTC. Lights are turned on by using mechanical relay.

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One Comment

  1. I love projects like this, but honestly there are off shelf versions of this available inexpensively.

    Honeywell makes a 7 day programmable version that you can set to turn on/off at sunrise/set–you program your long/lat and there is a correction factor in case there are some local obstacles like trees/mountains/buildings that may make you want the lights on/off longer.

    It is UL listed, has a rechargeable battery to go through power outages, adjusts itself for daylight savings times, fits in a single gang electric box, has a random on/off function if you’re away, and has a back-lit LCD.

    All for about $45.

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