Here’s a sunrise alarm clock that keeps perfect time. It was designed and built by [Renaud Schleck] who also published a post detailing the process.
As you can see, a series of white LEDs inside of the transparent case which provide the simulated sunrise. As the days get short and the nights longer we do see the benefit of having your clock brighten the room before it jolts you out of your slumber. Speaking of, that alarm sound seems to be the weak link in his design. He’s using a square wave smoothed with capacitors to drive a speaker at either end of the case. We didn’t hear an example but we imagine this not the most gentle of sounds.
The rest of the design is quite well done. He’s using a 4×20 Character LCD display and adjusts the backlight using PWM. A DCF77 radio feeds data from an atomic clock signal to the MSP430 chip which runs the clock. There’s even a battery backup in case the power goes out.
We just saw a project yesterday that aims to improve signal quality with a DCF77 radio.