Assembly of Mechanically Scanned LED Display

Figure 1 

The project aims to build a mechanically scanned LED display that can function as an analog and a digital clock.

As an analog clock, it can display seconds, minutes, hours, and hour markers while the hands run through all other display data. As a digital clock, it can display time, weekday, date, and year wherein the Time/Date format is in European style. Every 4 minutes, the full size 64×32 logo changes over to a 96 bit wide scrolling message. The year display runs around while the scrolling message is active.

The device is featured with PIC16F876-20 microcontroller, separate DC motor to drive the rotor, dial scanning, synchronization in the form of a 480-pulse optical shaft encoder, LED bar with 35 rectangular dual LEDs having 32 green & 3 yellow, diameter of 1m across, power transfer to PCB via 3 ball bearings, and rotation speed of 300-400rpm.

The brightness of the LED can be controlled using an LM317 adjustable voltage regulator. Since the ball bearings will not always conduct perfectly, the main power supply should be at least 12V. the noise on the arm is being suppressed by a series resistor and capacitor.

Rest of the project