Row-columm Scanning to control an 8x8 LED Matrix

LED displays are often packaged as matrixes of LEDs arranged in rows of common anodes and columns of common cathodes, or the reverse. Here's a typical example, and its schematic:

These can be very useful displays. To control a matrix, you connect both its rows and columns to your microcontroller. The columns are connected to the LEDs cathodes (see Figure 1), so a column needs to be LOW for any of the LEDs in that column to turn on. The rows are connected to the LEDs anodes, so the row needs to be HIGH for an individual LED to turn on. If the row and the column are both high or both low, no voltage flows through the LED and it doesn’t turn on.

To control an individual LED, you set its column LOW and its row HIGH. To control multiple LEDs in a row, you set the row HIGH, then take the column high, then set the columns LOW or HIGH as appropriate; a LOW column will turn the corresponding LED ON, and a HIGH column will turn it off.

Tip - Pins set to OUTPUT by use of the PinMode command are set to LOW if not otherwise stated

Although there are pre-made LED matrices, you can also make your own matrix from 64 LEDs, using the schematic as shown above.

It doesn’t matter which pins of the microcontroller you connect the rows and columns to, because you can assign things in software. Connected the pins in a way that makes wiring easiest. A typical layout is shown below.

Here's a matrix of the pin connections, based on the diagram above:

Matrix pin no.	Row	Column	Arduino pin number
1	5	-	13
2	7	-	12
3	-	2	11
4	-	3	10
5	8	-	16 (analog pin 2)
6	-	5	17 (analog pin 3)
7	6	-	18 (analog pin 4)
8	3	-	19 (analog pin 5)
9	1	-	2
10	-	4	3
11	-	6	4
12	4	-	5
13	-	1	6
14	2	-	7
15	-	7	8
16	-	8	9

Step 1: What You Need?

1 x Arduino Board ( Arduino UNO R3 used in this tutorial.)
1 x 8x8 LED Matrix 
2 x Potentiometer (10k Ohm) 
1 x Breadboard
1 x USB Type-B Cable 
Female-to-Male Jumper Wires


Optional 

Arduino Uno R3 Acrylic Transparent Casing

Arduino Compatible UNO Ultimate Starter Kit / Learning Kit

Don't have components? Don't worry. Just click the component's name. 

Step 2: Build Your Circuit.

The 16 pins of the matrix are hooked up to 16 pins of the Arduino board. Four of the analog pins are used as digital inputs 16 through 19. The order of the pins is assigned in two arrays in the code.

Two potentiometers, connected to analog pins 0 and 1, control the movement of a lit LED in the matrix.

Step 3: Upload The Code.

1. Select the Arduino board type: Select Tools >> Board >> Select your correct Arduino board used.

2. Find the port number by accessing device manager on Windows. See the section Port (COM&LPT) and look for an open port named "Arduino Uno (COMxx)". If you are using a different board, you will find a name accordingly. What matters is the xx in COMxx part. In my case, it's COM3. So my port number is 3.

Select the right port: Tools >> Port >> Select the port number.

3. You can find this code in the example of Arduino IDE.

Select File >> Examples >> 07. Display >> RowColumnScanning

Click press the "upload" button (see the button with right arrow mark).

Download:

Arduino IDE

Sources:https://www.arduino.cc/en/Tutorial/RowColumnScanning

07.Display 8x8 LED Matrix library

LED Bar Graph

The bar graph - a series of LEDs in a line, such as you see on an audio display - is a common hardware display for analog sensors. It's made up of a series of LEDs in a row, an analog input like a potentiometer, and a little code in between. 

This tutorial demonstrates how to control a series of LEDs in a row, but can be applied to any series of digital outputs.

This tutorial borrows from the For Loop and Arrays tutorial as well as the Analog Input tutorial.

Step 1: What You Need?

1 x Arduino Board ( Arduino UNO R3 used in this tutorial.)
1 x LED Bar Graph Display or 10 x LEDs 
1 x Potentiometer
10 x 220 Ohm Resistors 
1 x Breadboard
1 x USB Type-B Cable 
Male-to-Male Jumper Wires


Optional
Arduino Uno R3 Acrylic Transparent Casing
Arduino Compatible UNO Ultimate Starter Kit / Learning Kit

Don't have components? Don't worry. Just click the component's name.

Step 2: Build Your Circuit.

Step 3: Upload The Code.

1. Select the Arduino board type: Select Tools >> Board >> Select your correct Arduino board used.

2. Find the port number by accessing device manager on Windows. See the section Port (COM&LPT) and look for an open port named "Arduino Uno (COMxx)". If you are using a different board, you will find a name accordingly. What matters is the xx in COMxx part. In my case, it's COM3. So my port number is 3.

Select the right port: Tools >> Port >> Select the port number.

3. You can find this code in the example of Arduino IDE.

Select File >> Examples >> 07. Display >> barGraph

Click press the "upload" button (see the button with right arrow mark).

The sketch works like this: first you read the input. You map the input value to the output range, in this case ten LEDs. Then you set up a for loop to iterate over the outputs. If the output's number in the series is lower than the mapped input range, you turn it on. If not, you turn it off.

Download:

Arduino IDE

Sources:https://www.arduino.cc/en/Tutorial/BarGraph

07.Display LED Bar Graph library