Introduction
Seven-segment displays are a widely used electronic display technology
that presents numerical information. They are found in digital clocks,
calculators, electronic meters, and many other devices requiring a simple
numeric display. This blog post delves into the types of seven-segment displays
and their detailed working.
What is a Seven-Segment Display?
A seven-segment display consists of seven LEDs (light-emitting diodes)
arranged in a rectangular fashion. Each LED segment can be lit up individually
to represent numbers from 0 to 9 and some alphabetic characters. The seven
segments are labelled from 'a' to 'g'.
Types of Seven-Segment Displays
1. Common Anode (CA):
o In a common anode
display, all the anodes (positive terminals) of the LED segments are connected
together and to a high voltage (usually 5V).
o To illuminate a segment, you apply a low voltage (0V) to the cathode (negative terminal) of that segment.
2. Common Cathode (CC):
o In a common cathode
display, all the cathodes (negative terminals) of the LED segments are
connected together and to ground (0V).
o To illuminate a
segment, you apply a high voltage (usually 5V) to the anode (positive terminal)
of that segment.
Pin Configuration
A standard seven-segment display has 10 pins: one for each of the seven
segments, a pin for the common anode/cathode, and sometimes additional pins for
the decimal point and other functionalities.
Working of Seven-Segment Displays
Common Anode Display
1. Connecting the
Display:
o Connect the common
anode to the positive supply voltage.
o Connect each segment
to a microcontroller or any control circuit through current-limiting resistors
to avoid burning out the LEDs.
2. Controlling the
Segments:
o To light up a
segment, you need to pull its corresponding pin to ground (0V).
o For example, to
display the number "8", you would pull all segment pins (a to g) to
ground.
Common Cathode Display
1. Connecting the
Display:
o Connect the common
cathode to ground (0V).
o Connect each segment
to a microcontroller or any control circuit through current-limiting resistors.
2. Controlling the
Segments:
o To light up a
segment, you need to apply a high voltage to its corresponding pin.
o For example, to
display the number "8", you would apply a high voltage to all segment
pins (a to g).
Practical Example: Displaying Numbers
To illustrate, let's consider how to display different numbers on a
seven-segment display:
- Number 0: Segments a, b,
c, d, e, and f are lit.
- Number 1: Segments b and
c are lit.
- Number 2: Segments a, b,
d, e, and g are lit.
- Number 3: Segments a, b,
c, d, and g are lit.
- Number 4: Segments b, c,
f, and g are lit.
- Number 5: Segments a, c,
d, f, and g are lit.
- Number 6: Segments a, c,
d, e, f, and g are lit.
- Number 7: Segments a, b,
and c are lit.
- Number 8: All segments
are lit.
- Number 9: Segments a, b,
c, d, f, and g are lit.
Applications
Seven-segment displays are versatile and can be used in various
applications:
- Digital Clocks: Displaying
hours, minutes, and seconds.
- Calculators: Displaying
digits and basic mathematical symbols.
- Meters: Voltage,
current, and frequency meters often use seven-segment displays.
- Home
Appliances: Microwaves, washing machines, and other appliances to display time,
temperature, or settings.
Final Remarks
Seven-segment displays are fundamental components in digital electronics,
providing a simple and effective way to display numerical information.
Understanding the types (common anode and common cathode) and how to control
each segment is crucial for effectively integrating them into your projects.
Whether you're building a digital clock, a calculator, or any device requiring
numeric display, seven-segment displays are an excellent choice.