![Seven segment 01 Pengo](https://upload.wikimedia.org/wikipedia/commons/e/ea/Seven_segment_01_Pengo.jpg)
A seven-segment display is a form of electronic
display device
A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal the ...
for displaying
decimal
The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral ...
numerals
A numeral is a figure, symbol, or group of figures or symbols denoting a number. It may refer to:
* Numeral system used in mathematics
* Numeral (linguistics), a part of speech denoting numbers (e.g. ''one'' and ''first'' in English)
* Numerical d ...
that is an alternative to the more complex
dot matrix display
A dot-matrix display is a low cost electronic digital display device that displays information on machines such as clocks, watches, calculators, and many other devices requiring a simple alphanumeric (and/or graphic) display device of limited res ...
s.
Seven-segment displays are widely used in
digital clock
A digital clock is a type of clock that displays the time digitally (i.e. in numerals or other symbols), as opposed to an analogue clock.
Digital clocks are often associated with electronic drives, but the "digital" description refers only to ...
s, electronic meters, basic calculators, and other electronic devices that display numerical information.
History
Seven-segment representation of figures can be found in
patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...
s as early as 1903 (in ), 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 (). 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
LED
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
s in the 1970s.
![Incandescent light seven-segment display prPNr°17](https://upload.wikimedia.org/wikipedia/commons/a/ad/Incandescent_light_seven-segment_display_prPNr%C2%B017.jpg)
Some early seven-segment displays used incandescent filaments in an evacuated bulb; they are also known as numitrons. A variation (minitrons) made use of an evacuated
potted Potting may refer to:
* Potting, in pottery, the making of pots, generally on the potter's wheel
* Potting (electronics), the encapsulation of electronic components
* In farming and gardening, potting is planting a plant in a pot, such as a flowe ...
box. Minitrons are filament segment displays that are housed in DIP packages like modern LED segment displays. They may have up to
16 segments. There were also segment displays that used small incandescent light bulbs instead of LEDs or incandescent filaments. These worked similarly to modern LED segment displays.
Vacuum fluorescent display
A vacuum fluorescent display (VFD) is a display device once commonly used on consumer electronics equipment such as video cassette recorders, car radios, and microwave ovens.
A VFD operates on the principle of cathodoluminescence, roughly s ...
versions were also used in the 1970s.
Many early (c. 1970s) LED seven-segment displays had each digit built on a single
die
Die, as a verb, refers to death, the cessation of life.
Die may also refer to:
Games
* Die, singular of dice, small throwable objects used for producing random numbers
Manufacturing
* Die (integrated circuit), a rectangular piece of a semicondu ...
. This made the digits very small. Some included magnifying lenses onto the design in an attempt to make the digits more legible.
The seven-segment pattern is sometimes used in posters or tags, where the user either applies color to pre-printed segments, or applies color through a seven-segment digit
template
Template may refer to:
Tools
* Die (manufacturing), used to cut or shape material
* Mold, in a molding process
* Stencil, a pattern or overlay used in graphic arts (drawing, painting, etc.) and sewing to replicate letters, shapes or designs
Co ...
, to compose figures such as product prices or telephone numbers.
For many applications, dot-matrix LCDs have largely superseded LED displays in general, though even in LCDs, seven-segment displays are common. Unlike LEDs, the shapes of elements in an LCD panel are arbitrary since they are formed on the display by
photolithography
In integrated circuit manufacturing, photolithography or optical lithography is a general term used for techniques that use light to produce minutely patterned thin films of suitable materials over a substrate, such as a silicon wafer, to protect ...
. In contrast, the shapes of LED segments tend to be simple
rectangle
In Euclidean plane geometry, a rectangle is a quadrilateral with four right angles. It can also be defined as: an equiangular quadrilateral, since equiangular means that all of its angles are equal (360°/4 = 90°); or a parallelogram containi ...
s, reflecting the fact that they have to be physically moulded to shape, which makes it difficult to form more complex shapes than the segments of 7-segment displays. However, the high recognition factor of seven-segment displays, and the comparatively high visual
contrast obtained by such displays relative to dot-matrix digits, makes seven-segment multiple-digit LCD screens very common on basic
calculator
An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics.
The first solid-state electronic calculator was created in the early 1960s. Pocket-sized ...
s.
The seven-segment display has inspired
type design
Type design is the art and process of designing typefaces. This involves drawing each letterform using a consistent style. The basic concepts and design variables are described below.
A typeface differs from other modes of graphic production su ...
ers to produce typefaces reminiscent of that display (but more legible), such as
New Alphabet
New Alphabet is a parametric typeface designed by Wim Crouwel, released in 1967. It embraced the limitations of the display technology that it was displayed on by only using horizontal and vertical strokes. This meant that some of the letters ha ...
, "DB LCD Temp", "ION B", etc.
Using a restricted range of letters that look like (upside-down) digits, seven-segment displays are commonly used by school children to form words and phrases using a technique known as "
calculator spelling
Calculator spelling is an unintended characteristic of the seven-segments display traditionally used by calculators, in which, when read upside-down, the digits resemble letters of the Latin alphabet. Each digit may be mapped to one or more let ...
".
Implementations
![7segment multiplexing](https://upload.wikimedia.org/wikipedia/commons/a/a4/7segment_multiplexing.gif)
Seven-segment displays may use a
liquid crystal display
A liquid-crystal display (LCD) is a flat panel display, flat-panel display or other Electro-optic modulator, electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liqui ...
(LCD), a
light-emitting diode
A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
(LED) for each segment, an
electrochromic display, or other light-generating or controlling techniques such as
cold cathode
A cold cathode is a cathode that is not electrically heated by a filament.A negatively charged electrode emits electrons or is the positively charged terminal. For more, see field emission. A cathode may be considered "cold" if it emits more el ...
gas discharge (Panaplex),
vacuum fluorescent (VFD),
incandescent filaments (Numitron), and others. For
gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
price totems and other large signs,
vane display
A vane display is a type of 7-segment display. Unlike LED and VFD segmented displays, vane displays are composed of seven physical surfaces (vanes), typically painted white, but occasionally other colors, such as yellow or fluorescent green. If ...
s made up of electromagnetically flipped light-reflecting segments (or "vanes") are still commonly used. A precursor to the 7-segment display in the 1950s through the 1970s was the cold-cathode, neon-lamp-like
nixie tube
A Nixie tube ( ), or cold cathode display, is an electronic device used for displaying numerals or other information using glow discharge.
The glass tube contains a wire-mesh anode and multiple cathodes, shaped like numerals or other symbols ...
. Starting in 1970,
RCA
The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...
sold a display device known as the ' that used incandescent filaments arranged into a seven-segment display.
In USSR, the first electronic calculator "Vega", which was produced from 1964, contains 20 decimal digits with seven-segment
electroluminescent display
Electroluminescent Displays (ELDs) are a type of flat panel display created by sandwiching a layer of electroluminescent material such as GaAs between two layers of conductors. When current flows, the layer of material emits radiation in the form ...
.
In a simple LED package, typically all of the
cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
s (negative terminals) or all of the
anode
An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...
s (positive terminals) of the segment LEDs are connected and brought out to a common pin; this is referred to as a "common cathode" or "common anode" device.
Hence a 7 segment plus decimal point package will only require nine pins, though commercial products typically contain more pins, and/or spaces where pins would go, in order to match standard
IC sockets. Integrated displays also exist, with single or multiple digits. Some of these integrated displays incorporate their own internal
decoder
Decoder may refer to:
Technology
* Audio decoder converts digital audio to analog form
* Binary decoder, digital circuits such as 1-of-N and seven-segment decoders
* Decompress (compression decoder), converts compressed data (e.g., audio/video/im ...
, though most do not: each individual LED is brought out to a connecting pin as described.
Multiple-digit LED displays as used in pocket calculators and similar devices used
multiplexed display
Multiplexed displays are electronic display devices where the entire display is not driven at one time.
Instead, sub-units of the display (typically, rows or columns for a dot matrix display or individual characters for a character oriented dis ...
s to reduce the number of I/O pins required to control the display. For example, all the anodes of the A segments of each digit position would be connected together and to a
driver circuit
In electronics, a driver is a circuit or component used to control another circuit or component, such as a high-power transistor, liquid crystal display (LCD), stepper motors, SRAM memory, and numerous others.
They are usually used to regula ...
pin, while the cathodes of all segments for each digit would be connected. To operate any particular segment of any digit, the controlling integrated circuit would turn on the cathode driver for the selected digit, and the anode drivers for the desired segments; then after a short blanking interval the next digit would be selected and new segments lit, in a sequential fashion. In this manner an eight digit display with seven segments and a decimal point would require only 8 cathode drivers and 8 anode drivers, instead of sixty-four drivers and IC pins. Often in pocket calculators the digit drive lines would be used to scan the keyboard as well, providing further savings; however, pressing multiple keys at once would produce odd results on the multiplexed display.
Although to a naked eye all digits of an LED display appear lit, only one digit is lit at any given time in a multiplexed display. The digit changes at a high enough rate that the human eye cannot see the flashing (on earlier devices it could be visible to peripheral vision).
Characters
![7 Segment Display with Labeled Segments](https://upload.wikimedia.org/wikipedia/commons/e/ed/7_Segment_Display_with_Labeled_Segments.svg)
The seven segments are arranged as a rectangle of two vertical segments on each side with one horizontal segment on the top, middle, and bottom. Often the rectangle is ''
oblique
Oblique may refer to:
* an alternative name for the character usually called a slash (punctuation) ( / )
* Oblique angle, in geometry
*Oblique triangle, in geometry
*Oblique lattice, in geometry
* Oblique leaf base, a characteristic shape of the b ...
'' (slanted), which aids readability. In most applications, the segments are of nearly uniform shape and size (usually elongated
hexagon
In geometry, a hexagon (from Ancient Greek, Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple polygon, simple (non-self-intersecting) hexagon is 720°.
Regular hexa ...
s, though
trapezoid
A quadrilateral with at least one pair of parallel sides is called a trapezoid () in American and Canadian English. In British and other forms of English, it is called a trapezium ().
A trapezoid is necessarily a Convex polygon, convex quadri ...
s and
rectangle
In Euclidean plane geometry, a rectangle is a quadrilateral with four right angles. It can also be defined as: an equiangular quadrilateral, since equiangular means that all of its angles are equal (360°/4 = 90°); or a parallelogram containi ...
s can also be used), though in the case of
adding machine
An adding machine is a class of mechanical calculator, usually specialized for bookkeeping calculations.
In the United States, the earliest adding machines were usually built to read in dollars and cents. Adding machines were ubiquitous off ...
s, the vertical segments are longer and more oddly shaped at the ends in an effort to further enhance readability. The seven elements of the display can be lit in different combinations to represent the
Arabic numerals
Arabic numerals are the ten numerical digits: , , , , , , , , and . They are the most commonly used symbols to write Decimal, decimal numbers. They are also used for writing numbers in other systems such as octal, and for writing identifiers ...
.
The segments are referred to by the letters A to G, where the optional
decimal point
A decimal separator is a symbol used to separate the integer part from the fractional part of a number written in decimal form (e.g., "." in 12.45). Different countries officially designate different symbols for use as the separator. The choi ...
(an "eighth segment", referred to as DP) is used for the display of non-integer numbers.
A single byte can encode the full state of a 7-segment-display including the decimal point. The most popular bit encodings are ''gfedcba'' and ''abcdefg''. In the ''gfedcba'' representation, a byte value of 0x06 would turn on segments "c" and "b", which would display a "1".
Decimal
The
numerical digit
A numerical digit (often shortened to just digit) is a single symbol used alone (such as "2") or in combinations (such as "25"), to represent numbers in a positional numeral system. The name "digit" comes from the fact that the ten digits (Latin ...
s 0 to 9 are the most common characters displayed on seven-segment displays. The most common patterns used for each of these is:
:
Alternate patterns: The numeral 1 may be represented with the left segments, the numerals 6 and 9 may be represented without a "tail", and the numeral 7 represented ''with'' a 'tail':
[For example the fx-50F calculator from ]Casio
is a Japanese multinational electronics manufacturing corporation headquartered in Shibuya, Tokyo, Japan. Its products include calculators, mobile phones, digital cameras, electronic musical instruments, and analogue and digital watches. It ...
and other models from the same manufacturer.
:
In Unicode 13.0, 10 codepoints had been given for segmented digits 0–9 in the
Symbols for Legacy Computing
Symbols for Legacy Computing is a Unicode block containing graphic characters that were used for various home computers from the 1970s and 1980s and in Teletext broadcasting standards. It includes characters from the Amstrad CPC, MSX, Mattel Aqu ...
block, to replicate early computer fonts that included seven-segment versions of the digits. The official reference shows the less-common four-segment "7". The characters as displayed by your browser:
Hexadecimal
Four binary bits are needed to specify the numbers 0–9, but can also specify 10–15, so usually decoders with 4 bit inputs can also display
Hexadecimal
In mathematics and computing, the hexadecimal (also base-16 or simply hex) numeral system is a positional numeral system that represents numbers using a radix (base) of 16. Unlike the decimal system representing numbers using 10 symbols, hexa ...
(Hex) digits. Today, a combination of uppercase and lowercase letters is commonly used for A–F;
this is done to obtain a unique, unambiguous shape for each hexadecimal digit (otherwise, a capital "D" would look identical to a '0' and a capital 'B' would look identical to an '8').
Also the digit '6' must be displayed with the top bar lit to avoid ambiguity with the letter 'b'.
:
Letters
Most letters of the
Latin alphabet
The Latin alphabet or Roman alphabet is the collection of letters originally used by the ancient Romans to write the Latin language. Largely unaltered with the exception of extensions (such as diacritics), it used to write English and the o ...
can be reasonably implemented using seven segments. Though not every letter is available, it is possible to create many useful words. By choosing better
synonym
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
s, it is possible to work around many shortcomings of seven-segment alphabet encodings. Some uppercase letters ('I', "O", "S", "Z") look identical to numerical digits ('1', '0', '5', '2'), though it is possible to use lower-case "o" and "i", or putting "I" on the left. Lowercase letters "b" and "q" are identical to the alternate numerical digits '6' and '9'. Depending on the situation, some of these problem characters can be used when no numeric values are used in the same word/phrase, see examples below.
Short messages giving status information (e.g. "no dISC" on a CD player) are also commonly represented on 7-segment displays. In the case of such messages it is not necessary for every letter to be unambiguous, merely for the words as a whole to be readable.
Examples:
:, , , , ,
:, , , , , ,
:, , , , ,
Seven-segment displays have also been used to show letters of the
Cyrillic
, bg, кирилица , mk, кирилица , russian: кириллица , sr, ћирилица, uk, кирилиця
, fam1 = Egyptian hieroglyphs
, fam2 = Proto-Sinaitic
, fam3 = Phoenician
, fam4 = G ...
and
Greek alphabet
The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BCE. It is derived from the earlier Phoenician alphabet, and was the earliest known alphabetic script to have distinct letters for vowels as we ...
s:
There are enough patterns to show all the letters but few representations are unambiguous and intuitive at the same time. When all letters need to be displayed on a device,
sixteen-segment and
dot matrix
A dot matrix is a 2-dimensional patterned array, used to represent characters, symbols and images. Most types of modern technology use dot matrices for display of information, including mobile phones, televisions, and printers. The system is al ...
displays are better choices than seven-segment displays.
Punctuation
Seven segments are capable of displaying some
punctuation
Punctuation (or sometimes interpunction) is the use of spacing, conventional signs (called punctuation marks), and certain typographical devices as aids to the understanding and correct reading of written text, whether read silently or aloud. An ...
glyph characters. The
hex value for each
Unicode
Unicode, formally The Unicode Standard,The formal version reference is is an information technology Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expre ...
character is shown.
Decoder ICs
In the past, some seven-segment decoder
ICs didn't output the following modern decimal/hexadecimal font.
:
* For "1", the MC14558B displays the number on the left side of the display using segments "e" and "f" instead of the usual "b" and "c".
* For "7", the TC5022 displays it with additional segment "f".
* For "6" and "9", the CD4511B, MC14558B, TC5002, SN74x46/SN74x47/SN74x48/SN74x49 displays both numbers without a "tail", where "x" is the
TTL logic family.
* For "A" to "F":
:* BCD decoder ICs support various seven-segment fonts for their decoded output of "A" (10) to "F" (15) inputs.
:* The
7446/7447/7448/7449 and the
Siemens
Siemens AG ( ) is a German multinational conglomerate corporation and the largest industrial manufacturing company in Europe headquartered in Munich with branch offices abroad.
The principal divisions of the corporation are ''Industry'', '' ...
FLH551-7448/555-8448 chips used truncated versions of "2", "3", "4", "5" and "6" for digits A–E. Digit F (1111 binary) was blank.
:* The TC5002 and TC5022 repeat the numbers 0 to 5 for digits A–F.
:* The MM74C912 displayed "o" for A and B, "−" for C, D and E, and blank for F.
The CD4511B just displayed blanks.
:* Soviet
programmable calculator
Programmable calculators are calculators that can automatically carry out a sequence of operations under control of a stored computer programming, program. Most are Turing complete, and, as such, are theoretically general-purpose computers. Howe ...
s like the
Б3–34 used the symbols "−", "L", "C", "Г", "E", and " " (space), allowing the error message
EГГ0Г to be displayed.
:
See also
![Common segment displays](https://upload.wikimedia.org/wikipedia/commons/d/d1/Common_segment_displays.svg)
There are also fourteen- and sixteen-segment displays (for full
alphanumeric
Alphanumericals or alphanumeric characters are a combination of alphabetical and numerical characters. More specifically, they are the collection of Latin letters and Arabic digits. An alphanumeric code is an identifier made of alphanumeric ch ...
s); however, these have mostly been replaced by dot matrix displays. Twenty-two-segment displays capable of displaying the full
ASCII
ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...
character set
were briefly available in the early 1980s but did not prove popular.
*
Eight-segment display
An eight-segment display is a type of display based on eight segments that can be turned on or off according to the font pattern to be produced.
It is similar to a nine-segment display whose middle vertical bars are vertical, except that on an e ...
*
Nine-segment display
A nine-segment display is a type of display based on nine segments that can be turned on or off according to the graphic pattern to be produced. It is an extension of the more common seven-segment display, having an additional two diagonal or ver ...
*
Fourteen-segment display
A fourteen-segment display (FSD) (sometimes referred to as a starburst display or Union Jack display) is a type of display based on 14 segments that can be turned on or off to produce letters and numerals. It is an expansion of the more com ...
*
Sixteen-segment display
A sixteen-segment display (SISD) is a type of display based on sixteen segments that can be turned on or off to produce a graphic pattern. It is an extension of the more common seven-segment display, adding four diagonal and two vertical segments ...
*
Dot matrix display
A dot-matrix display is a low cost electronic digital display device that displays information on machines such as clocks, watches, calculators, and many other devices requiring a simple alphanumeric (and/or graphic) display device of limited res ...
*
Nixie tube
A Nixie tube ( ), or cold cathode display, is an electronic device used for displaying numerals or other information using glow discharge.
The glass tube contains a wire-mesh anode and multiple cathodes, shaped like numerals or other symbols ...
display
*
Vacuum fluorescent display
A vacuum fluorescent display (VFD) is a display device once commonly used on consumer electronics equipment such as video cassette recorders, car radios, and microwave ovens.
A VFD operates on the principle of cathodoluminescence, roughly s ...
References
External links
Interactive Demonstration of a Seven Segment DisplayInterfacing 7 Segment Display with AVR Microcontroller
{{Display technology
Display technology