Segment Displays
Inside Segment Displays
Segment Displays contain LEDs arranged in a specific fashion such that, various characters or shapes can be displayed, by turning ON selective segments in different combinations. Shape of the LED is rectangular (to appear as a segment).Generally, these are used to display numbers. As of now, alpha-numeric characters can also be displayed using 16-Segment display.
Basically, there are two types of displays based on common node of LEDs inside the display. The configurations shown below are for Seven segment displays, which contain seven segments and a dot point (decimal point) to show floating values.
1. Common Cathode Segment Display
2. Common Anode Segment display
Segment Identification
Each segment is assigned with an alphabet for identification with respect to the pin-out in the available packages depending on the size and number of segments of the display. This segment identification is same for both common anode and common cathode displays.
Based on number of segments, there are :
1. 7-segment displays
2. 14-segment displays
3. 16-segment displays
Moving from lower to higher number of segments, the readability and number of
characters that can be framed using the display increases.
Segment Displays Available in Proteus
Proteus contain all the segment displays mentioned above i.e., seven, fourteen,
sixteen Segment displays. Lower versions (version 7.0) contain only seven segment displays.
Whereas, higher version 7.7 and above contain all the three types. It has displays of
different colors which gives spectacular real-time appearance and this feature comes into
handy while presenting the projects or finalizing the circuits.
There are multiplexed displays available, which are formed by multiplexing several single digit
displays(the segment pins of multiple single digit displays are combined, leaving the common node pins separately). This technique reduces the number of pins required by the control circuit IC to interface with the display. Multiplexed packages reduces the PCB layout complexity and soldering work. These multiplexed displays are generally named after their number of digits. For example, 2 Digit display contains two single digits multiplexed.
Segment displays are found in components under the category of ‘Optoelectronics’. The description of the display gives information about its common node, i.e., whether it is common cathode or common anode, number of digits, color of the LEDs.
To select segment displays,
Step 1: Select component mode
Step 2: Click on Pick devices ‘P’ .
Step 3: Type Segment in the Keyword textbox and select the required display.
Using Segment Displays
The technical parameters of LEDs of the segments like Forward Voltage Drop and Forward current are available in the datasheets. Using those parameters and depending on the voltage level of the IC that is used to drive the segment, a series resistance has to be connected to each LED segment for its safe operation while implementing in hardware. Generally, as a thumb rule 330Ω resistance is sufficient when the voltage level of the driver IC or the microcontroller is 5V.This value is obtained from the formula used in the previous chapter (Chapter 2 on LEDs).
Rs = (Vsource – Voltage drop of LED)/Maximum Forward Current
The pin configurations of the displays in Proteus for various displays are as follows:
The following circuit shows the usage of seven segment display with common anode and
common cathode.
Step 1: Select component mode
Step 2: Click on Pick devices ‘P’ .
Step 3: Type Segment in the Keyword textbox and select the 1 Digit seven segment display with common anode and common cathode.
Step 4: Select 8-element DIP Switches with common terminal.
Step 5:Select power and ground terminals from terminals tab.
Step 6: Connect the circuit as per the circuit diagram.
Screenshot 3.7
Circuit diagram for seven segment display usage
Step 7: Run the simulation.
Simulation of Seven Segment Display Usage
Simulation of Sixteen Segment Display Usage
Character Generation Through Microcontroller in 16-Segment Display
Similarly, other segment displays can also be used.
Basics of using Multiple Digit Displays
Using multiplexed displays require microcontrollers. But, the technique can be explained with discrete components similar to previous examples. Using microcontrollers will be explained after covering few basic chapters.
Step 1: Select component mode
Step 2: Click on Pick devices ‘P’ .
Step 3: Type Segment displays in the Keyword textbox and select the 4 digit 7 segment common
Cathode display, 8- Element DIP Switch.
Step 4: Select power and ground terminals from terminals tab.
Step 5: Connect the circuit as per the circuit diagram.
Multiplexed Displays Usage
The switching actions done manually are performed by the microcontrollers at a speed (refresh
rate) that is not recognized by the naked eye. This technique is applicable for all the displays.
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