Time Transporter

Some microcontroller applications such as  those which log or track information often  require current time and date information  to be stored along with the collected data.  A Real Time Clock (RTC) chip such as the IC  DS1307 with battery back-up can be used to  supply the required information. This particular chip easily integrates into most designs  using the absolute minimum of external components. The process of programming the  chip in software is simple and is supported in  the majority of programming environments.  Intrinsic functions, header files and libraries are widely implemented for the device. A  quick trawl of the Internet will uncover lots of  programming examples.

So far so good except that the chip first needs to be programmed with the current time and date information. This information is maintained and updated (thanks to a keep-alive battery) even when the external circuitry is shut down. To carry out the programming requires connection to a keyboard and display but the additional hardware will only ever be needed for this one-off event.
Circuit diagram :
Time Transporter Circuit Diagram
Time Transporter Circuit Diagram
The design suggested here solves  the problem by combining the IC, battery, crystal and peripheral components  onto a tiny plug-in PCB. The circuit consists  of a small square of prototyping perf board  onto which is mounted the IC, a crystal, battery, decoupling capacitor (C1) and two  (optional) pull-up resistors for the open collector outputs. An IC socket with extra longs  pins (or two modular connector strips) completes the design. The complete RTC module (see photo) is self contained and can be  plugged from one circuit to another using  its long pins without losing track of time and  date. The only requirement in the target sys-tem is space for an 8-way DIL socket, wiring  to the socket and software to read the time  information.
The essential advantage with this  approach is that hard and software  expenditure in the target system is  kept to a minimum, it will only ever  need to read the time and date information. The extra hardware and soft-ware required to set both time and  date are assigned to a separate sys-tem, maybe a dedicated breadboard  design.
Once programmed the ticking clock  module can then simply be transferred to the target system.

Author :Jochen BrĂ¼ning - Copyright : Elektor


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