Seven Segment Display

A seven-segment display, also written as 7-segment display, is an optoelectronic device used for displaying numerals. It consists of seven individually controlled LED segments that provide a numeric display for digital electronic systems. It usually consists of seven segments labelled a, b, c, d, e, f, g, and an eighth LED for the decimal point DP. Applications include interfacing with digital systems where a numerical display is required. GCSE Students use it for digital gate projects involving shift registers, and decoder circuits, and even interfacing to a Raspberry Pi.

The 0.36 inch (9.14 mm) size is the standard size used in school and hobby projects. Other sizes available are as follows.

  • 0.56 inch
  • 0.8 inch
  • 1 inch
  • 1.5 inch
  • 2.3 inch
  • 4 inches

These displays are available in single digit, double digits, three digits, and four digits modules, and they all have dedicated pinout arrangements. A quad display provides a four-digit display.

Although the more widely used displays are numeric types, you can also get alphanumeric displays, which displays the letters of the alphabet and numerals, because they consist of more segments.

Forward Current and Voltage

If you are planning to interface this display to a microcontroller, then you will need to calculate the value of the series resistors from the forward current of the segment in the display. The colours available are red, blue, green, yellow, and white, and the forward current is different for different colours. For example, a typical 0.36-inch digit size display has the typical forward currents, and forward voltages shown in the table below.

Display Colour Forward Current Vf - Typical
Red 30 mA 1.8 V
Green 25 mA 1.9 V
Blue 30 mA 3.3 V
Amber 30 mA 1.8 V
White 20 mA 3.3 V

Please use my LED Resistor Calculator page for calculating the resistor values.

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Seven Segment Display
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