Drive the multiplexed 4 digit 7-segment display

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Seven segment displays are widely used in clocks, meters and other devices that need to display numerical information. The elements of the display, which are usually made from LEDs, are lit in different combinations to represent Arabic numerals. They have a limited ability to display some characters because there are only 7 elements that compose the shape of the displayed figure. Seven segment displays are very easy to find and are the cheapest display type.

In the previous post I talked about the electrical connections of such displays and how they should be interfaced to a microcontroller (MCU). A 7-segment display requires current limiting resistors on each segment and transistor drivers for each digit. This time I will identify the pins of an unmarked display device, I will wire it on the breadboard to an Arduino Nano compatible board and I’ll attempt to write the software to drive it.

Drive the multiplexed 4 digit 7-segment display

Proper wiring of a 4 digit 7-segment display

 Author:   Posted on:    No comments
Seven segment displays are widely used in clocks, meters and other devices that need to display numerical information. The elements of the display, which are usually made from LEDs, are lit in different combinations to represent Arabic numerals. They have a limited ability to display some characters because there are only 7 elements that compose the shape of the displayed figure.

Seven segment displays are very easy to find and are the cheapest display type. Nowadays, modules with such displays do exist, where a display of 4, 8 and even more digits are driven by an integrated circuit. This driver gets the digits to be displayed from a microcontroller (MCU) via a serial bus. This saves a lot of pins and makes programming easy since all modern MCUs have support for the common serial protocols. Examples of such ICs are MAX7219, TM1637 and TM1638. The latter two come with support for keypad, therefore you can build front panels with buttons and display using such ICs.

Proper wiring of a 4 digit 7-segment display