Aniruddha Deb

Electronic Clock I - Getting Started

This is a new series in which I will describe all the steps I went through while creating an electronic clock. Make sure you’re subscribed to the RSS feed so that you don’t miss out on anything!

Getting Started

An electronic clock is a good project for intermediate to advanced electronic hobbyists, which is why I decided to build one.

The first task is enumerating the requirements of the clock. A humble requirement list looks like this:

  • Clock should run on a few AA cells
  • It should have a 24 hour display
  • It should display seconds, minutes and hours
  • It should have two LED’s each to separate the hours, minutes and seconds
  • It should be moderately compact
  • It should be challenging to engineer and design

The second task is deciding what components will form the base of the clock (akin to choosing a language or a technology stack for developing an application). For a clock, a few options are available:

  • Use a microcontroller:
    • Interface a DS1307 clock module with the microcontroller using SPI, or
    • Write your own code for a real-time clock in the microcontroller and use an external clock crystal (already done this here)
  • Use CMOS/TTL Logic IC’s

I decided to go with the second option as I had already written code for a microcontroller clock and gone halfway through the implementation when I realized that it was too easy and did not provide a challenge. If you are a beginner, you should take the microcontroller route, as in case of bugs, they are easily rectifiable via your code, whereas debugging a hardware circuit (especially a large CMOS/TTL one) is decently hard for beginners.

Within a few minutes, I drew a basic block diagram for the main components in the circuit.

The circuit mainly consists of a 1Hz signal generator, a few counters/dividers and the display logic.

In the next segment, I’m going to build the signal generator and produce an accurate 2Hz signal that can be used by the other counters.

- Deb