Sep 15th, 2019 | by: ELECTRONOOBS | Views 6610
Views 6610
In this tutorial we make a SCROLLING DOT MATRIX device with Bluetooth connection and a real time clock to show time, date, temperature and day of the week. I've made an Android app to control this and change speed, brightness and select modes and also to send text to be scrolled on the display. See the parts we need, how to connect them, upload the code and test the display. Let's start.
PART 1 - What we need

We need a few simple parts. The Arduino, of course to run the code and 9 dot matrices modules. I've tried more than 9 but the library can't do more than that so 9 is max. To receive wireless data I've used the HC06 Bluetooth module and to get the real time, I've used a DS3231 real time clock. We need a few more parts to regulate the voltage and charge the batteries. And yes, we need 2 18650 batteries with a 2S BMS module to charge them. The case is made out of plywood and with carbon fiber vinyl on top.

Partw we need
PART 2 - Schematic

The schematic has a few connections. Let's start from the power part. To charge the betteries we need to give exactly 8.4V to the BMS board. So, from the 12V DC trasnformer jack, connect the buck converter and set it to 8.4V. Then add a sliding switch to separate the circuits. Connect the BMS mdoule to the 2 batteries in series. Then at the output add the on and off switch and at the output of this switch add another small buck converter and set this one to 5V. The Arduino has a voltage regulator but is not powerful enough.

Then connect the RTC module to the Arduino. The Bluetooth module uses the RX and TX pins. So make sure you upload the code before you connect the module, otherwise the code won't uplaod. We can't have anything connected to the TX and RX pins when we uplaod the code. Go below, downlaod it and uplaod it. Then connect the Bluetooth module and the dot matrices in series as in the schematic above.

PART 3.1 - Mount it all

First, make the circuit on a breadbaord and test if it works. Also, see the direction of the LED matrices in order to know how to place those inside the case. Go below and downlaod the code and the App and give it a test. See if you receive the text, set time, etc.

Test the circuit
PART 3.2


Now, we make the power part. Connect the BMS to the battery. Connect the DC jack of the transformer to the big buck converter and set it to 8.4V. Then connect that to the sliding swithc and that to the BMS input/output. From there add the on and off switch and that to the second buck converter and set it to 5V. Now we have our voltage and we can connect that to the Arduino and modules.

Set the voltage
PART 3.3


Ok, now we connect all the matrices in series. Make some measurements and cut some plywood parts to make the case. Then make then hole for 9 matrices on the front part. Place all matrices in that hole and use some hot glue to fix them in place. Add the side walls of the case and then we could connect all the modules. But first go below and downlaod the code and upload it. Then we connect the modules.

Mount the case
PART 3.4

Now add all the modules, I glue the batteries on the back plywood and add everythiong. Put the on off swithc on top of the case and glue everything. Now I can close the case. Remember to uplaod the code from next step. Now you could let the case like this or add that carbon fiber vinyl.

Finish the wood case

PART 3.5


Ok, make some measurements and cut the vinyl to size. Add the vinyl and then I sue the heat gun to glue it even better. Cut the holes for the on and off switch and for the matrices. Now the case is ready. Below you have the next step for code and the Android App.

Add vinyl
PART 4 - Code

Ok, before you close the case and add the Bluetooth module, go below and downlaod the full code. You will need to download the library as well and install it to the Arduino IDE. You have the library on that same link below. Once you upload the code, go to next step and get the Android app and install it to your smartphone.

#include "MaxMatrix.h"
#include "avr/pgmspace.h"

int data = 11;    // DIN pin of MAX7219 module
int load = 12;    // CS pin of MAX7219 module
int clock = 13;  // CLK pin of MAX7219 module

PART 5 - The App

Downlaod the App and copy the .apk file to your Android smartphone. Then enable unknown origin apps to be able to install on your phone. Install the app. Enable Bluetooth on your phone and search for devices. Turn on the matrix. Select the HC06 module and pair with 1234 or 0000 password. Then open the app, click the Bluetooth icon and select the HC06 module. Now you can send text or select modes.

The App in AppInventor
PART 6 - The Video

See the video of the project for more. Consider supporting my work on PATREON. Thank you!


  • Fabrizio Mundaca

    about 5 years ago

    i have the 4 in 1 matrix and it shows each single matrix turned out 90 degrees to the left. how can i make it work out with this matrix?


    about 5 years ago

    You will need a different library See here httpwwwelectronoobscomengarduinotut14php

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  • Celeste 2123

    about 4 years ago

    Hola, me encantó este proyecto. Soy nueva y estoy aprendiendo a crear mis app en appinventor y quisiera saber si es posible que me pasarás el archivo del proyecto de la app. Aún no logró poder enviar un mensaje al BT del Arduino y que este me visualice el texto en un LCD. Sería de muchas ayudar si podrías facilitar está información para seguir con mi aprendizaje. Desde ya muchas gracias y Éxitos 🤩

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