arduino 8×8 led matrix scrolling text
It made with 256 10 millimeter diameter green LEDs, it’s controlled by an Arduino and 4 LED drivers, each driver for each 8×8 matrix. It can display text shapes and great. A screwing effect of your text connect your smartphone to it open the app type your desired text and press send. So now let’s see how to create this huge, LED, matrix, let’s up my friends. We’Ll come back in order to build our awesome huge, LED matrix. We will need a bunch of LEDs. I’Ve used this 10 millimeter diameter made green LEDs. Our matrix will have eight rows and 32 columns. That will give us a total of 256 LEDs before we start building it. I would like to explain a little bit how this type of matrices work. Any one color LED diode has two pins. One is called anode and is the positive one and usually it’s longer than the other one. The other one is called cathode and is the negative one, just as any other diode. This component only allows current to flow in one direction, in this case, from the positive side to the negative one. So let’s say that this LED works with five volts. So if we connect the kettle to ground and apply five volts to the anode, the LED would shine. So what we will do is take a bunch of these LEDs and connect their kettles in series creating eight rows. We do the same for the anodes, but for each eight columns, not for the entire 32 that the matrix has now we have all these negative pins of the LEDs connected and the positive pins as well.
These are for 8×8 matrices, but later we will join them together, using the LED drivers now let’s say that we want to turn on this specific LED. Obviously we should connect ground to the road number 4 and 5 volts to column. Number 5 is right, but now let’s say that we want to light up the a letter like this, since we want to display text let’s start by looking at this vertical bar of the a letter. So we need to turn on 8 LEDs of this column. For that, we should connect ground to these 8 rows and 5 volts only to this column. To now everything is ok. Now let’s look to the next column in order to display the a chapter we should turn on these two LEDs of this color, and here is our first problem. We have already connected ground to the rows 0 to 8 in the previous step. In order to turn on the previous column, so if now we connect 5 volts to this column in order to turn on only these two LEDs, the entire column will turn on, but we want to turn on only to let so how we do that. Well, this is the solution. We power up only one row at a time like this, but we do it fast enough that the human eye won’t be able to see the switch. So now let’s go back to the a letter we first power up the 5 LEDs of the first row in a fraction of second, we turn off those 5 LEDs and turn on the next two of the second row.
We do the same for all 8 rows and start again. Well, this doesn’t look like the a letter. Definite let’s increase a little bit the switch speed as you can see when the speed gets high enough. Our eyes can tell the difference anymore and combine together all the rows, creating the a letter. Okay. So now we know how this LED matrices work, but now, if we want to switch each row and each column led of each row, we should connect 32 wires to the columns and eight wires to the rows. That is a huge amount of connections. Besides, I want to use an Arduino Nano to control the LED matrix and Arduino Nano doesn’t. Have that amount of digital pins so to reduce the connection and improve the circuit, we will use the Mac 7219 LED matrix driver. Each of these drivers can control an 8×8 LED matrix. All we need to do is connect the clock, load and data pin from the Arduino feed. In this way, we can send the data in the zero communication and the driver will create a parallel output of each of the eight columns and eight rows. Once we complete our 8 by 8 matrix, we could connect four of these in series, creating a huge 8 by 32 matrix. All we need to do is to connect the data pin out from the first driver to the second, the data pin from the second to the third and so on.
In this way, we could build a huge LED matrix using just one Arduino and three pins to send the data. Basically, this is how any LED matrix work. Okay, so let’s build this thing. I’Ve started by cutting two 19 by 25 centimeters 4 millimeters thick balsa wood sheet. This will be the front and, back of my LED matrix case, I have also used to 19 centimeters long 1 centimeter thick piece of wood like this one, also 23 centimeter long for the side. Using these four pieces of wood, we will create the case. I will use this 1 centimeter diameter LEDs. I want to separate each LED 2.5 centimeters between each other. I make all the measurements and make sure that the LED measures will be centered on the wood sheet. I mark the spot for each hole now using a nine millimeter drill bit. I will drill all the holes. I make the holes a little bit smaller, so the LEDs will fit in tight drilling all the 256 holes takes quite some time actually was the longest part of the entire project. Okay, so the main board is ready before I placing the LEDs. I want to create some sort of case and paint. This board white so will reflect more light. I spray paint the board and let it dry now we can start placing the LEDs. This is also a very long time job. We have to place each LED in this position.
We start from the left side of the board. Each LED will have the negative pin to the right and the positive one to the left. Once the LED is in place. We went the positive pin towards the bottom of the board flat on the surface like this. Now we add the next seven LEDs in the same way as the first one. Now we solder the entire column in series from the first positive pin of the first led to the left leg of the bottom. We are done with the first column. We do the same for all of the thirty two columns once finished. We do the same for the rows, but this time we won’t bend the negative pin fat on the wood surface. We have to leave about one centimeter between the pin and the board bend the negative pin of each led to the right like this now using some solid wire solder them together in groups of eight lights per row, owlette matrix is done. We now have four eight by eight matrices that create a 32 by eight one. Finally, I glue four pieces of foam into small boards between the LEDs. This is where I place all the electronic parts and leave the glue to dry and start the electronic part of this tutorial to create our circuit I’ve used this schematic. You could download the schematics cause an example from a link below, as always so, each Mac 7219 driver could control an 8 by 8 matrix.
We start by soldering the first one on the drilled PCB I solder the Arduino Nano and the first max driver. I supply 5 volts and ground and connect the data, clock and load pins. I also solder a 10 micro farad capacitor and the 40 K ohms resistor. Now I can connect all the wires to the first matrix, which is the left one. I first order all the negative pins be careful by following the schematic. There are a lot of connections now I solder the positive things and the first matrix is ready using another drill PCB i solder the second driver, I supply clock and low pins from the Arduino, but the data pin isn’t connecting to the Arduino like the previous one. The data in pin is the data out of the first driver. I do the same for the rest of the drivers and we are done. The matrix is alive. I upload an example code and test it out, works perfect. To close the case, I glue and nail II place the site drill, a hole for the USB cable and we are done to supply the matrix. I’Ll use a normal smartphone, 5 volts charger. I pass the USB cable through the hole and fix it in place. Using a zip tie, connect the USB to the Arduino, and now I can close the case. I flip around the metrics and we are done it looks so nice so now let’s take a look at the code.
First of all, you have to download the LED control library for the arduino ide. You could use the library manager of the arduino to search it and install it or you could download it from a link below you will download a zip file to install it. Open arduino ide go to sketch, include library and add the zip library here open the downloaded zip file and you are done now, let’s open the code. This is the code for our scrolling led metrics, download it and open it in arduino ide. Here we define our used pins in the previous kinetic I’ve used, pin 10 11 and 13 as the data clock and load pins in an ohm devices. We add the 4 because we are using 4 8 by 8 batteries in series to change the text to display just edit this drink. Now we start the communication and the drivers. These are all the chapters that we could print. So if you want to change one just edit these vectors, finally, at the bottom, we send each vector for each chapter in the serial communication. Ok upload the code and we are done in the next video. We will see how to control these metrics using a Bluetooth connection. For now our project is done. I hope that you enjoyed it. If you have any questions, just leave it in the comment section below or my QampA page subscribe to my channel.
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