“First, why call it the Crap Clock? Well, it lowers expectations with the hope of exceeding them :-) Also there is an LED on the seconds display which will never light due to a bit of short sighted design.
Second, this ain’t really a how to make the ‘thing’ more a reflection on design choices and all the materials you need to go about building your own.
The Crap Clock is a clock running from a ATMEGA328 which drives 82 LEDs via a 74HC595 driving the rows and a TLC5940 sinking the current across the columns. As DS3231 keeps the time and can be kept running with the battery input terminals. The clock has several modes to view the time, date, year, temperature and then modes for setting the time and date with the two buttons. The LEDs can be dimmed with the TLC5940 and the seconds display (Pink LEDs above) can be used to display a contextual letter alongside the mode the clock is in.
There are a couple of features I have not used or have taken out of the PCB like Li-ion battery charging, I did that in this version to reduce the cost of the parts and because the DS3231 really only sips a small amount of current. There are still pins for the inbuilt DS3231 alarm INT/SQW pin and a buzzer pin from the ATMEGA. Pin 10 is broken out for general use and there is also an analog pin available for a feature like a LDR to alter brightness based on the ambient light.
I put together a playlist of all the videos where I can remember talking about or designing the Crap Clock.”