seven segment display

1. BACKGROUND
 Seven-segment representation of figures can be found in patents as early as 1903 (in U.S. Patent
1,126,641), when Carl Kinsley invented a method of telegraphically transmitting letters and numbers and
having them printed on tape in a segmented format. In 1908, F. W. Wood invented an 8-segment
display, which displayed the number 4 using a diagonal bar (U.S. Patent 974,943). In 1910, a seven-
segment display illuminated by incandescent bulbs was used on a power-plant boiler room signal panel.
They were also used to show the dialed telephone number to operators during the transition from
manual to automatic telephone dialing.They did not achieve widespread use until the advent of LEDs in
the 1970s.

2. INTRODUCTION
•A Digital Decoder IC, is a device which
converts one digital format into another
and one of the most commonly used
devices for doing this is called the Binary
Coded Decimal (BCD) to
7-Segment Display Decoder.
•7-segment LED (Light Emitting Diode) or LCD
(Liquid Crystal Display) type displays, provide a
very convenient way of displaying information or
digital data in the form of numbers, letters or
even alpha-numerical characters.

3. CONCEPT OF DECODER AND ITS USE
 A Digital Decoder IC, is
 a device which converts
 one digital format into
 another and one
 of the most commonly
 used devices for doing
 this is called the Binary
 Coded Decimal (BCD)
 to 7-Segment Display
 Decoder.

4. CATHODE AND ANODE DISPLAY
 In electronics there are two important types of 7-segment LED digital display:
1. The Common Cathode Display (CCD) – In the common cathode display, all the cathode connections of
the LED’s are joined together to logic “0” or ground. The individual segments are illuminated by
application of a “HIGH”, logic “1” signal to the individual Anode terminals.
2. The Common Anode Display (CAD) – In the common anode display, all the anode connections of the
LED’s are joined together to logic “1” and the individual segments are illuminated by connecting the
individual Cathode terminals to a “LOW”, logic “0” signal.

5. EXAMPLE
 An example of the 4-bit BCD input ( 0100 ) representing the number “4” is
given below.

6. WORKING DIAGRAM OF 7-SIGMENT DISPLAY

7. TRUTH TABLE

8. EXPLANATION

9. CURRENT USE
 Seven-segment displays are widely used in digital clocks, electronic meters, basic calculators, and other
electronic devices that display numerical information.
 Seven-segment displays may use a liquid crystal display (LCD), a light-emitting diode (LED)
 Seven-segment displays are also use to display arabics letter and alphabets

10. FUTURE APPLICATION AND MODIFICATION
 There are also fourteen-segment displays and sixteen-segment displays
(for full alphanumerics); however, these have mostly been replaced by dot
matrix displays.
 Twenty-two segment displays capable of displaying the full ASCII
character set were briefly available in the early 1980s, but did not prove
popular.Dictation