Self-powered wireless ambient light sensor

Since some time, the window blinds in our home are automatically controlled. When the sun rises they go up, at sunset they are closed.

To determine the correct time for the blind commands, I’ve written a mix of Perl scripts. There exists a handy Perl module to calculate sunrise/sunset based on the date and your location on earth. After some fiddling with the parameters, I have a setup that works rather good. However, the Perl module does not take into account the weather. On bright and cloudless days, the blinds can stay open a bit longer. When we’re on the other hand experiencing our typical North Sea autumn weather, they can safely be closed a bit earlier.

Enter some electronics 😉

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DCF controlled time switch

I needed a way to automatically control the main heating of my parents house. The basic idea is to start the heating at a certain time in the morning, and to switch it off at night. The switching points are different on various weekdays.

Of course, I could have bought a time switch. However, those things alway tend to have too much or too little switching points, an inaccurate clock, or they are just too complicated to be programmed (ok, this is relative, but you’ll agree with me that time switches with an RS232 port for programming are not really common ;-).

One of the first things I planned to make once I learned working with microcontrollers was a DCF77 time decoder. I never found the time to actually start building one, so this was the perfect excuse. I decided to make a PIC-controlled time switch that gets its time updated through the DCF77 radio signal.
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