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Internet Time Display Module For The WIB

Looking for a really accurate clock? This simple add-on board for the WIB (Web Server In A Box) displays the time and date, as gathered from an internet time server. You can use it as a clock you never need to adjust and it can even be configured in the WIB to automatically adjust for daylight saving time.

By Mauro Grassi

WIB Time Display Module: Main Features

• Displays local time and date derived from an internet time server

• Can be configured in the WIB to automatically adjust to daylight saving time

• Six different display modes for time and date (including static and scrolling displays)

• Three line interface to the WIB with automatic baud rate adjustment

• Persistent settings (settings stored in EEPROM)

In the November & December 2009 issues of SILICON CHIP, we published the WIB (Web Server In a Box), an ethernet-based web server with a memory card. This simple add-on board allows the time and date to be displayed on a 7-segment 4-digit LED display. The time is gathered from the internet and is re-synchronised every 10 minutes by the WIB for update on the display.

In operation, the time and date information gathered by the WIB is sent to the add-on module via the on-board serial port. The hours, minutes, seconds, day, month and year can all be displayed. A single pushbutton switch allows you to scroll through the time and date readings or you can set the unit to automatically scroll through the time and date displays.

Click for larger image
Fig.1: the circuit uses microcontroller IC1 to process the serial data from the WIB PC board. IC1 then drives four 7-segment LED displays in multiplex fashion via switching transistors Q1-Q12.

Circuit operation

Take a look now at the circuit diagram of Fig.1. It’s based on a single microcontroller (IC1), in this case a PIC18F1320. Apart from that, there’s just the four 7-segment LED displays, 12 transistors to drive the displays and a handful of minor parts.

To keep the cost down, an 8MHz RC oscillator internal to IC1 is used as the system clock. Its accuracy is quite sufficient for our purposes – it really only affects the baud rate of the UART (universal asynchronous receiver/transmitter) used to receive the time and date information from the WIB and in any case, the baud rate is synchronised automatically to the baud rate of the UART in the WIB (more on this later).

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