Wrist Watch LED Timepiece Known as Microdot

Overview

The project pertains to a circuit board used in making futuristic wrist watch size timepiece made of LEDs with more functions applicable to a portable device.

Explanation

The microdot can be made into several different sizes and shapes although traditional microdots are usually circular around one millimeter in diameter. The time is basically shown by a random distribution of different colored LEDs and the number of LEDs in each color corresponds to the time. To light up a LED requires a simple programming of the microcontroller to send a logic 1 or a logic 0 to whichever two control lines that correspond to the LED and set the others to inputs.

A PIC16F88 microcontroller used contains 2 ports for selecting serial inputs, ADC, 8kb Flash ROM, and 368 bytes of RAM. It also has an onboard oscillator which can be connected to a common watch crystal for timekeeping and low power modes. Even when the device is in low power mode, the timekeeping oscillator can still run.

To control a number of LEDs is by taking advantage of the tri-state nature of the microcontroller pins and the forward voltage of the LEDs.