This accurate clock project is developed based on the GPS Receiver which captures a time signal from the U.S. government’s global positioning system (GPS) satellites and parses it to extract time syntaxes from NMEA string to finally display on 7-segment displays. The transmitter on GPS clock then broadcasts the time to every other nearby wireless clock and make them run in synchronization with same accuracy. GPS clock is developed using Atmel’s Atmega32L microcontroller with Fastrax GPS receiver module and six digit seven segment displays. For a particular installation there will be two types of clocks – one Master GPS clock and many Slave wireless clocks.
Sunil Jha, the project designer, explained that in Master GPS clock, Atmega 32 microcontroller decodes NMEA string from GPS receiver to obtain the time values. It then display time on seven segment LEDs and also transmits the same NMEA string wirelessly through local 2.4 GHz link established using Zigbee transceiver modules. The slave wireless clocks contain Zigbee Transceiver modules, Atmega 32 microcontroller, and seven segment displays. It works similar to Master GPS clocks except that the NMEA string is received through local wireless link instead of GPS receiver. Within wireless range many slave clocks can b installed reducing overall implementation cost.