Introducing Seven Segment Display

Numerous applications require may an electronic system to display certain information on the control panel. Example can be frequency or voltage of an electric generator or RPM of an engine. The most widely used display in use at commercial, industrial and on residential applications is a “Seven Segment Display”. A seven segment display is a type of display that uses specially placed LED to show numbers and digits. Each digits consist of minimum of 8 LED. By selectively turning ON & OFF the specific segment LED, we can create both numbers (0-9) and some English alphabets. These displays are made of 7 LED. Each of these LED is called segment. As there are 7 LED , there are 7 segments and the display is therefore called Seven Segment Display.

In reality, there are 8 LED and 8 segments. Seven segment display has a dot on the lower right corner of the display. This dot can be used to display numbers with decimal. The dot is also made of LED. However, the dot is not always used and the 7 segments can be used to display any number from 0 to 9. So dot segment is not considered a segment itself..

For 8 segments/LED, there should be total of 8×2 pins i.e. total of 16 pins. To reduce the number of physical pin, during manufacturing, either all Anode or all cathode of the segments/LED are tied together to form one physical pin. Therefore, these displays are manufactured as two variants.

i. Common Anode (all LED anode tied together)

ii. Common Cathode (all LED cathode tied together)

Seven segment display are sold in multiple form. The display can have 1 digit or multiple digits. For a single digit display, each display has 10 pins. 7 pins for 7 segments, 1 pin for the dot segment and 2 common COM pin. The common COM pins are electrically connected to each other. Segments of the display is named a,b,c,d,e,f,g and dot. Every single segment has an input pin. By applying a voltage on the input pin, that specific segment is turned ON. The user can apply voltage on specific segments by themselves to light up the specific segment(s).