Print this pageClock Design
The clock system runs on a PIC microcontroller system. The core of the system is prototype board supplied by Modtronix. This board SBC44B use a 44 pin PIC16F877A and has a RS232 interface, a Real Time Clock (RTC), a I2C interface and additional expansion sockets. The boards have worked well, been cost effective and are well supported by the Modtronix.
The software development was with the SourceBoost IDEand C compiler. SourceBoost was selected due to the combination of functionality, active support forum and competitive price. It can certainly be recommended.
The battery backed RTC keeps system time whilst the system is off. The I2C interface connects to the RTC, a small 4 x 20 Serial LCD Display and a 12 key keypad.
The main displays are a set of 6 '7 segment' LED character displays, these modules are produced by Vellman. The START time display is in the main enclosure and a second remote display is in a second enclosure conected by a 25m simple serial cable. The displays are controlled by a simple message protocol sent over the RS232 interface. The displays and other small components are available from Rapid Electronics and Maplin.
The sound output uses a pair of 556 timers to generate the long and short beeps when signalled by a trigger from one of the PIC ports.
The displays require power supply of 9 to 12Vdc with 120mA per display, this is achieved with a 12 volt 7 Amp Hour sealed lead acid battery which also powers the main board.
The enclosure was specially commisioned from Custom Design Technologies Ltd as no off the shelf item was available.
The support from Modronix, SourceBoost, Rapid and Custom Design all contributed to the success of the project. Thanks.
Development: A software rewrite is underway to increase efficiency using interupts and a 'Real Time Operating System' again part of the SourceBoost system. An approach which seems appropriate for a Clock project.
Block Diagram and Pictures
Pictures go here.