The clock consists of 4 independent modules which work in sync to display the time. Each module consists of 2 28byj48 stepper motors and 2 9g metal gear servos. The stepper motors push the chains out one segment at a time and the servos bend them according to each digit. The chains home to know positions using magnets and hall sensors in the tips of the chains at the beginning of each digit. Currently I have only one of the digits working but eventually will get them all to work . One of the module consists of an additional ds1304 module to take care of the time and coordinate the rest over the serial link.