I wanted a clock which is always on correct time. Of course that should be in UTC-time, because I’m going to use it with my ham radio hobby. The clock is using a AVR-microcontroller and a RTC-chip. Synchronization is made from a GPS and time (and date) is shown on LCD-display. There is also a connection for a computer, that can be used to synchronize the computer.
The data from the GPS is read trough RS232/TTL-converter. The microcontroller will parse the data and update the RTC-chip. The RTC-chip is running independently with it’s own clock-crystal. There is also a battery backup for RTC, so time continues running while the other circuit is powered down. The connection for a computer can be configured in two ways. The data can be read straight from the GPS, or from the microcontroller. This can be selected with jumpers on the board. There is also two EEPROM-chips on the board for future applications. LCD-connection is standard HD44780-connection. Depending on a size of the LCD, there can be shown also other information from GPS, like a latitude and longitude. I have also a option for a digital temperature sensor. Some other connections has been included also for the future applications, so I don’t need a new board when I want to add something.
Here is the circuit:
The final board (without the lcd and an enclosure):