Summary of Dot Matrix Scrolling Mesage using AVR microcontroller
This project creates a Dot Matrix Scrolling Sign using an AVR microcontroller and LTR-747HR displays. The system employs three 74HC595 shift registers to sequentially control columns while PORTB manages the registers and PORTD sends column data. A ULN2003 driver amplifies signals to switch LEDs on and off, forming scrolling characters within 3ms intervals.
Parts used in the Dot Matrix Scrolling Sign:
- AVR microcontroller
- LTR-747HR Dot matrix display
- Three 74HC595 shift register ICs
- ULN2003 signal amplifier
- PCB board
- Two 10 pin flat cable connectors
- attinyboard or STK500
Description
This is a Dot Matrix Scrolling Sign. A Dot Matrix Display has an 5×7 led matrix with 5 columns and 7 rows. The display is controlled by the AVR microcontroller. The rows are controlled by PORTB of the microcontroller, while PORTD puts the data on the columns to make the characters. The Dot matrix display used here is the LTR-747HR and is 0.7 inch (17.8mm) high.
Hardware
The circuit is stand alone and can be connected to the ports B and D off the AVR microcontroller. The circuit consists of three shift registers IC’s 74HC595 which switches each column of the displays sequentially on and off for 3ms. PORTB controls the the 74HC595. When a column is selected, the data for the column is put on PORTD, the signals from PORTB are amplified by the ULN2003, and switches the LED’s on and off. While each column is swithed on and off seqeuntially, the characters on the display are formed. The PCB contains all the parts except for the microcontroller part. The PCB has to be connected via the two 10 pin flat cable connectors to the attinyboard or the STK500 for example.
For more detail: Dot Matrix Scrolling Mesage using AVR microcontroller
- How is the dot matrix display controlled?
The display is controlled by an AVR microcontroller where rows are managed by PORTB and data for columns is sent via PORTD. - What type of dot matrix display is used in this project?
The project uses the LTR-747HR which is 0.7 inch high with a 5x7 led matrix configuration. - Which components switch each column of the displays?
Three shift register ICs labeled 74HC595 switch each column sequentially on and off for 3ms. - What component amplifies the signals from PORTB?
The signals from PORTB are amplified by the ULN2003 before switching the LEDs on and off. - Can this circuit operate as a standalone unit?
Yes, the circuit is stand alone but requires connection to an attinyboard or STK500 via two 10 pin flat cable connectors. - How are characters formed on the display?
Characters are formed while each column is switched on and off sequentially using data placed on PORTD. - Does the PCB include the microcontroller?
No, the PCB contains all parts except for the microcontroller part.
