A seven-segment display is an arrangement of 7 LEDs are connected in a rectangular manner and Seven-segment displays are commonly used for both letters and numerical displays by logic and computer systems. Each LED is called a segment because it forms a part of the digit being displayed. Seven segment displays can be used to show any hexadecimal number between 0000 and 1111 by light up combinations of these LEDs.
The application of seven-segment displays is like digital clocks and electronic meters etc. The connection consists of two types common anode 7-segment display has all of the anodes tied together while a common cathode 7-segment display has all the cathodes tied together.
In forwarding biasing LEDs, we can display the digits from 0 to 9. For example, to display a 0, the LEDs A, B, C, D, E, and F are forward biased respectively. To light up a 6, we need to forward bias segments A, C, D, E, F, G. The particular set of LEDs is forward biased which is depending upon the digit to be displayed is used in seven-segment. The various digits from 0 to 9 which can be displayed using seven segment display are shown in the below-given figure
Methods To Connect Seven Segment Display
When dealing with the connection of seven-segment displays, there are two ways in which you can connect a seven-segment display
- Common Anode Type
- Common Cathode Type
Common Anode Type
In common anode type, all the anodes on the display are connected to a common pin, mostly the power source and the LED are controlled through the cathodes with the ground being on and power being off. A current resistor is to be connected between each LED and ground to limit the value of current.
Common Cathode Type
In common cathode type, all the cathodes are connected to a common pin, in this case generally ground connection and the LED is driven by the state of the anodes where the ground is off and power is on. A current resistor is connected between each LED and the supply + VCC to limit the current value.
In seven-segment display, a plus decimal point package will only require nine pins, though commercial products typically contain more pins in order to match industry-standard pinouts.
Truth Table Of Seven Segment Display
Truth Table Of Seven Segment Display can be used to show how to display each number on display. This can be seen in give Table below.
LED Driver Circuit For Seven Segment Display
Controlling a seven-segment display will need eight pins for mostly displays and for decimal point it requires nine pins. It requires a lot of wiring connections to the circuit. However, the use of a display driver makes our work easy by reducing the number of connections that’s pins required to four. It is a logic-based device that passed a 4-bit binary input which is decoded and translated into the correct pin values for the display in the seven-segment.
The output of a digital logic circuit is either 0 or 1. Where ‘0’ means low while 1’ means high. In the high state, we can say that output voltage is nearly 5 Volt and in the low state, it is almost 0 Volt. When the output of the digital circuit is high, both ends of LED are at 5Volts and it can not be forward biased hence will not give light. While when the output of the digital circuit is low, then high current will flow through LED as it becomes forward biased, and it will give light.