Clock Design

This is the original clock design. The SOA clocks were updated to the KitST Clock design in 2015

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, the original 12 volt 7 Amp Hour sealed lead acid batteries have been replaced with 12v NiMH batteries which gives a significant weight saving.

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 has been completeed 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.

Development:

  • Time data and synchronisation now comes from a GPS unit. The time pulse from the GPS ensures that all clocks are synchronised to one time source.
  • Further time options include simple setting of Summer ( DST ) time. Setting a Time Zone.
  • The slave clock now has a buzzer which sounds with each Start to help Pre Start officials.

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