Definiton of Seven Segment – The Seven Segment Screen is an Electronic component that can display decimal numbers through combinations of segments. Seven Segment Display is generally used in Digital Clocks, Calculators, Digital Counters or Counters, Digital Multimeters and also Digital Display Panels such as microwave ovens or digital temperature regulators. The first Seven Segment Display was introduced and patented in 1908 by Frank. W. Wood became widely known in the 1970s after its application to LEDs (Light Emitting Diodes).
Seven Segment Display has 7 Segments where each segment is controlled on and off to display the desired number. Numbers from 0 (zero) to 9 (Nine) can be displayed using multiple Segment combinations. In addition to 0 – 9, the Seven Segment Display can also display Hexadecimal Letters from A to F. Segments or elements on the Seven Segment Display are arranged into the number “8” shape which is slightly tilted to the right with the aim of making it easier to read. In some types of Seven Segment Displays, there is also the addition of a “dot” that indicates a decimal comma number. There are several types of Seven Segment Displays, including Incandescent bulbs, Fluorescent lamps (FL), Liquid Crystal Display (LCD) and Light Emitting Diode (LED).
LED 7 Segmen (Seven Segment LED)
One type of Seven Segment Display that is often used by Electronics hobbyists is 7 Segments that use LEDs (Light Emitting Diode) as the light. These 7 Segment LEDs generally have 7 Segments or line elements and 1 dot segment signifying a Decimal “comma”. So the total number of LED segments or elements is actually 8. The way it works can also be said to be easy, when certain segments or elements are given an electric current, the Display will display the desired number or digit according to the given combination.
There are 2 Types of 7 Segment LEDs, including “LED 7 Segments common Cathode” and “LED 7 Segment common Anode”.
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LED 7 Segments Common Cathode Type (Cathode)
In the LED 7 Segments of the Common Cathode (Cathode) type, the Cathode Foot in all LED segments is connected to 1 Pin, while the Anode Foot will be the Input for each LED Segment. The Cathode leg connected to 1 Pin is a Negative Terminal (-) or Ground while the Control Signal will be given to each LED Segment Anode Foot.
LED 7 Segment Common Anode Type (Anode)
In the LED 7 Segment type Common Anode (Anode), the Anode Foot in all LED segments is connected to 1 Pin, while the Cathode foot will be the Input for each LED Segment. The anode legs connected to 1 Pin will be given a Positive Voltage (+) and a Control Signal (control signal) will be given to each LED Segment Cathode Foot.
Basic Working Principles of Driver System on 7 Segment LEDs
The following are the Basic Diagram Blocks for controlling 7-Segment LEDs:
The Decoder block in the diagram above converts the input signal given into 8 paths, namely “a” to “g” and decimal points (commas) to on-on segments so as to produce the desired number or digit. For example, if the decoder output is a, b, and c, then the LED segment will light up to the number “7”. If the Input Signal is analog in shape, then an ADC (Analog to Digital Converter) is required to convert the analog signal to Digital before entering the Decoder Input. If the Input Signal is already a Digital Signal, then the Decoder will handle it on its own without having to use the ADC.
The function of the Driver Block is to provide enough electric current to the LED Segment/Element to ignite. In certain Types of Decoders, the Decoder itself can emit enough voltage and electric current to power the LED Segment then this Driver Block is not needed. In general, the driver to power these 7 segments is consisting of 8 Transistor Switches on each LED element.
Seven Segment Display Activation Table
| NUMBER | h | g | f | and | d | c | b | a |
| 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 |
| 1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 |
| 2 | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 1 |
| 3 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 1 |
| 4 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 0 |
| 5 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 1 |
| 6 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 |
| 7 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 |
| 8 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| 9 | 0 | 1 | 1 | 0 | 1 | 1 | 1 | 1 |
Note:
1 = ON (High)0 = OFF (Low)
