What Is a 7-Segment Display?
A 7-segment display is a simple display component that shows the digits 0-9 and some letters by lighting seven bar-shaped LEDs (plus usually a dot) in the right combinations.
How Does It Work?
Each segment is an LED, named with the letters a-g. To form the desired digit the correct segments are lit at once; for example, for "7" the top and the right three segments light up.
Common Anode and Common Cathode
One terminal of all the segment LEDs is common. In the common-cathode type the common terminal connects to ground and the segments are driven from positive; in the common-anode type it's the reverse. If the wrong type is chosen the display won't work.
| Property | Explanation |
|---|---|
| Segment count | 7 + dot (DP) |
| Types | Common anode / cathode |
| Multi-digit | Multiplexing |
Multiplexing (Multi-Digit)
For multiple digits, instead of driving each digit separately, the digits are lit and blanked very quickly in sequence. The eye perceives this as continuously lit; this saves pins.
Where Is It Used?
Digital clocks, counters, oven/microwave panels, measurement instruments and simple numeric displays.
Common Mistakes
- Current limit: a series resistor is needed for each segment LED.
- Wrong type: if common anode/cathode is mixed up, it won't light at all.
- Multiplex speed: if the refresh is slow, the display flickers.
Frequently Asked Questions
Does it show letters?+
Is a driver chip needed?+
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