| Schematic | Layout | Video clip | ||
 5x7.avi (~1.9Mb) |
|---|
In this project we use a 5x7 dot matrix LED to display two digits on it. Each digit is displayed by using a 3x5 pattern and one column separates the digits. The demo program is just a counter from 00 to 99 in about 500msec intervals. Therefore, the displayed sequence of 100 numbers is 00, 01, 02, ..., 99 repeated periodically.
| Schematic | Layout | Video clip | ||
|
5x7.avi (~1.9Mb) |
|---|
The LED display consists of 5x7=35 LEDs forming a matrix. The program updates the display column by column about 60 times in a second to prevent flickering. At each time interval, the PIC sinks the current from at most one LED which prevents its inputs from overloading. The transistor attached to each column serves 5 LEDs of that column, so with the 5mA current through each LED is protects the outputs of 74HC138 from overload. The 3-to-8 decoder on 74HC138 is used to reduce the number of connections to the PIC.
Last modified:Mon, Jan 23, 2023.
