How to Test a 7 Segment Display with a Multimeter

This site contains affiliate links to products. We may receive a commission for purchases made through these links.

Have you heard of seven-segment displays? These are normally utilized in different electrical applications, such as scales, timers, and alarm clocks. In today’s post, we will learn how you can test a seven-segment display.

But first, let’s dig deeper into what a seven-segment display is. 

What is a 7-Segment Display?

As you may know already, a seven-display is an electrical tool that can be utilized for showing numerals and some letters. Various numbers or letters can be signified by attaching various pins on display to the battery, turning on the LEDs in parallel. That activity introduces how to utilize a seven-segment display using only a resistor, a breadboard, a battery, and some wires. 

It comes in different colors and sizes and has numerous forward bias voltages based on how many LEDs make up every segment. You will find two types of display accessible: common anode and common cathode. 

In short, it’s an arrangement of seven LEDs and a separate LED for the decimal place. The display could create the digits zero to nine to show decimal numbers and could create the letters A to F, permitting hexadecimal to be displayed as well. 

The seven elements are organized in the form of a square-shaped “8” that is a bit leaned to the right. A slight inclination to the right is provided to enhance its readability. The other seven segment displays have an extra dot that can be utilized for showing decimal points.

Further, the segments might be based on incandescent bulbs, LED, LCD, or fluorescent lamps. 

How Does It Work?

As the name signifies, the seven segments plus the dotted segment are based on LEDs. It illuminates when the power is presented to a specific segment, and the desired light could be shown by powering the appropriate combination of LEDs.

The particular set of LEDs is lit depending upon the decimal digit to be shown. For example, to display the numerical digit four, you need to light up four of the LED segments, which correspond to B, C, F, and G. 

Hence, the different digits from “0 to 9” and characters from “A to F” could be shown using a seven-segment display. 

Common Cathode versus Common Anode 

Keep in mind that LED seven segment displays are of two types: common anode and common cathode.

  • Common cathode – The cathode of every LED segment is connected together as one common cathode. The anode terminals are left as input pins. In this scheme, it’s always tied to the ground, and the control signals are applied to the inputs.
  • Common anode – The anodes of LED segments are connected together as one common anode, while the cathode terminals are left as input. The configuration of the common anode is often linked to an ideal positive voltage, and the control signals are used to the inputs. 

The Internal Structure of 7 Segment Display

The simple LEDs in the seven-segment display are used to show the decimal character. All the LEDs are positioned at a 90-angle from a minimum of two LEDs. One pin of all the LEDs is typical. That pin chooses when the anode is cathode or common.

All the other pins come out of the package as a single pin for every LED. Every time a pin gets the power input of particular voltages, it then begins glowing. The particular dark color case is utilized to regulate the LED light to itself.

The light from one LED will not impact the other and offers a clean and clear output. The power limit of the LED is based on the other simple LED lights. It also utilizes the resistor for power protection. 

What about the decimal point? 

The decimal point is also accessible in some seven-segment displays. However, it’s not accessible in all displays. Keep in mind that the decimal point only raises the one number in the pins. The other circuit of the decimal point stays the same as the other LEDs.

The accessibility of the decimal point is to signify the decimal values. 

How Can You Use a 7 Segment Display?

The use of a seven segment display is quite straightforward with each type of board and device. Hence, it only needs to receive the input signal at input pins for every LED. It also needs a particular component and circuit to make the seven-segment safe.

You can add the resistor of 220 ohms at every input pin. The resistor will then lower down the voltages, but the overall value of 220 ohms is only for 5 volts output devices. The rise in voltage will result in an increase in the resistor.

For you to use the LED, you will find two ways: one is an integrated circuit (IC) that will take the four inputs and will produce the output data from zero to nine. Further, it can display some alphabets on the seven segments. 

How To Test 7 Segment Display?

A simple way to test a seven-segment display is through a digital multimeter. If you like any segment to glow, you need to supply VCC. However, the seven-segment display is nothing more than a group of LEDs organized in a particular order and of a specific shape.

Hence, like any order LEDs, it will surely burn if the current goes beyond the rated value. That’s why you use current limiting sensors. However, testing using that setup is time-consuming. That’s why you need to test the segments first with the help of a multimeter.

Remember that the printed code on the 7-segment display will have an A mark for the common anode and a CC mark for the common cathode. 

Here are the steps you need to follow in testing the seven-segment display:

  1. Get your digital multimeter and set it to diode mode. 
  1. Depending on which variant you will have, you need to make the necessary connections. 
  1. For common anode: Put the positive test lead of your multimeter on the center pin. Put the negative test lead on the segment pin you like to test.

For common cathode: Put the negative test lead of your digital multimeter on the center pin and put the positive lead on the segment pin you like to test. 

We hope you find the answer to your questions with our guide.

About The Author