LED matrix is an interesting electronic component that most of the electronics enthusiasts want to work with. LED matrices of many sizes are available. 8*8 LED matrix is a commonly used one. Diagram of an 8*8 LED matrix is given below. 64 LEDs will be there in an 8*8 LED matrix.
In normal case, for 64 LEDs, 128 control pins will be there (64 positive and 64 negative pins). If the negative pins of all the LEDs are shorted, 64 positive pins will be remaining. To control each LEDs individually, voltage at the positive terminal of corresponding LED have to be controlled. Normally digital output pins of microcontrollers are used for this purpose. In such way, 64 digital output pins from microcontroller have to be used to control 64 LEDs which is practically impossible. Our next aim is to control maximum LEDs using minimum digital output pins from microcontroller. This results in the design of LED matrix.
Internal circuit of an 8*8 LED matrix is given below. From the figure, it is clear that LEDs are arranged as a matrix inside LED matrix. If LEDs are arranged as a matrix, for controlling 64 LEDs, only 16 control pins are needed of which eight pins (16, 15, 11, 3, 10, 5, 6, 13) are connected to positive terminal of LEDs and remaining pins (4, 7, 2, 8, 12, 1, 14, 9) are connected to negative terminal of LEDs. One positive pin controls the voltage at the positive terminal of eight LEDs. Similarly, one negative pin controls the voltage at the negative terminal of eight LEDs.
Circuit to turn on the 1st LED is given below. From the diagram, it is clear that positive voltage is given to the 16th pin and negative voltage is given to the 4th pin of LED matrix. Positive voltage will be common to all the LEDs connected to the 16th pin of LED matrix and negative voltage will be common to all the LEDs connected to the 4th pin of LED matrix. But the only LED which gets both positive and negative voltage is the 1st LED. So 1st LED will turn on.
Circuit to turn on the 10th LED is given below. From the diagram, it is clear that positive voltage is given to the 15th pin and negative voltage is given to the 7th pin of LED matrix. Positive voltage will be common to all the LEDs connected to the 15th pin of LED matrix and negative voltage will be common to all the LEDs connected to the 7th pin of LED matrix. But the only LED which gets both positive and negative voltage is the 10th LED. So 10th LED will turn on.
In normal case, for 64 LEDs, 128 control pins will be there (64 positive and 64 negative pins). If the negative pins of all the LEDs are shorted, 64 positive pins will be remaining. To control each LEDs individually, voltage at the positive terminal of corresponding LED have to be controlled. Normally digital output pins of microcontrollers are used for this purpose. In such way, 64 digital output pins from microcontroller have to be used to control 64 LEDs which is practically impossible. Our next aim is to control maximum LEDs using minimum digital output pins from microcontroller. This results in the design of LED matrix.
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