When it comes to presenting text messages, scrolling text LED displays are highly helpful. They are frequently observed in buses, trains and toll plazas as well as at railway stations.

They are typically utilized in locations where a wide audience needs to see written material. A computer or smartphone can be used to refresh the text content on an LED display. Due to the adjustable brightness, the text message is visible both during the day and at night. Now let’s look at how to create an LED display and send updated messages using a laptop or smartphone.

Components Required

1. Arduino UNO
2. MAX7219 display module
3. HC-05 Bluetooth module
4. 5V 2A Power adapter
5. Jumper wires (M to F)- 10 pcs

Connect the components according to below given circuit diagram.

Circuit Diagram

Hardware Explanation

We are utilizing the (4 in 1) MAX7219 dot matrix display matrix in this module. To create an 8 X 32 dot matrix display, four 8 X 8 dot matrix displays are cascaded together. Using a straightforward SPI interface, the MAX7219 module enables us to operate an 8 by 8 LED matrix. Its 64 LED’s worth of data can be stored in its built in static RAM. The MAX7219 makes it simple to adjust the display’s brightness. It has all the components required to operate a microcontroller-based LED matrix display. In addition, it powers the seven segment displays and is employed anywhere 64 LEDs need to be controlled.

VCC, GND, DIN, CS, and CLK are its five pins. The power adapter provides 5V and GND to VCC and GND (5V 2A). The SPI protocol is used by the module. The Arduino SPI pins are 11 (MOSI), 12(MISO), and 13(SCLK). The Arduino UNO’s 13 (MOSI) pin is linked to the DIN (data in) pin. The Arduino UNO’s pins 3 and12 (SCLK) are connected to the CLK and CS pins, respectively. Any pin can be used as the chip choose pin: all you have to do is edit the program’s variable.

The project is made wireless with the help of the HC-05 Bluetooth module. We will be able to text messages to the MAX7219 display module from a mobile app by using the HC-05. The HC-05 module includes six pins: EN, VCC, GND, TXD, RXD, and STATE. It communicates via the UART protocol. RXD is connected to Arduino’s RXD. The VCC and GND are connected to the 5V and GND of Arduino.

Once the connections are done, connect the Arduino UNO to the laptops USB COM port and open the Arduino IDE.

Installation of Libraries in Arduino IDE

We must install the MD_MAX72XX and MD_Parola libraries by magicDesignes before uploading the code. Install both libraries by going to library manager and searching for “MD_MAX72XX” and “MD_Parola”. Please see the screenshots provided below

SCREENSHOTS

Now we are ready to install the code.

Code

Following the submission of the code, to see the desired message on the LED display, open the serial monitor, type it, and press Enter. The message will appear to be scrolling on the screen.

Utilizing our mobile device’s Bluetooth terminal app is an additional method of sending messages.

Message sending with a Bluetooth application.

The moment the circuit is turned on, the led on the HC- 05 module begins to blink. The module is not linked to Bluetooth, as indicated by the blinking red led. Take the actions listed below-

1. Activate the Bluetooth on your mobile devices. You will see the HC-05 among the devices that are available when scanning begins. After choosing the HC-05 and entering the password “1234”, your phone and the HC-05 will pair.
2. Get the “serial Bluetooth Terminal” application from the Google Play Store.
3. Launch the application. Choose “devices”>> You will notice HC-05 there. Once you select HC-05, the module will be connected to you.
4. The HC-05 will cease blinking once you are connected.

The message can now be sent via the Bluetooth terminal app, and the led display will show it.

Reset the Arduino board before sending a new message to avoid having messages overwrite one another.

Conclusion

In this method, we created a text LED display that scrolls and can be operated from a cell phone or laptop. You can leave a comment on any post if you are unsure about something. Our staff will be there to help.