AVR Color Clock

  
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This page describes a color clock that displays the time using two RGB LEDs, one for hours and one for minutes, showing time by using the standard color coding used for components (with two additional colors as the standard color coding only has ten colors and twelve is needed). The time could have been shown more analogue by fading the colors but
AVR Color Clock - schematic

then it would be harder to read as the human color perception is quite bad. With the discrete solution with 12 well defined steps for both hours and minutes it is possible to tell the time with an accuracy of five minutes, and this accuracy is often good enough. The reason I made this clock was that my wife has really bad sight and need strong glasses to read the clock, and putting on the glasses at night just to see the clock at night if she wakes up will really make her awake and make it hard to get back to sleep. So I made her this clock as my birthday present for her on her 26th birthday (October 2007) to make it possible for her to see what time it is without putting on her glasses. As you can see in the schematic to the right it is a very simple design. The clock is controlled by an ATMEGA88 that drives the two RGB LEDs directly. The RGB LEDs have 220ohm resistors for current limiting, as it turns out the color temperature gets about right when all resistors are the same for the RGB LEDs that I used. The two RGB LEDs are pulse width modulated by the built-in 6-channel PWM-circuit in the AVR. There is a status RG LED to indicate status of the DCF receiver, this is too driven directly by the AVR using only current limiting resistors (220/440ohms to get yellow when both are lit). The DCF receiver is a module that is just a radio that only outputs the DCF-time code according to the pulse width carrier modulation format...



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