Summary of New version of MAX7219 based 4-digit serial seven segment LED display
This article introduces the SPI7SEGDISP4.40-1R, a revised 4-digit seven-segment LED display board featuring an upgraded LTC-4727JS chip with three extra colon segments for time displays. The module uses a MAX7219 driver chip connected to Arduino pins via the LedControl library to control digit selection and segment activation, including specific handling for the additional colon LEDs.
Parts used in the SPI7SEGDISP4.40-1R Project:
- SPI7SEGDISP4.40-1R Board
- LTC-4727JS Seven Segment LED Display
- MAX7219 Driver Chip
- Arduino Board
- LedControl Library
This (SPI7SEGDISP4.40-1R) is a revised version of the previous SPI seven segment LED display (4 digit) board that displayed numerals and decimal points. The new version has a better quality seven segment LED display (LTC-4727JS) with three extra LED segments, as shown below. The additional colon segments are useful in projects where you need to display time (HH:MM or MM:SS).
The common cathode terminals (Digit 1, Digit 2, Digit 3, and Digit 4) of the four seven segment digits are connected to D3, D2, D1, and D0 pins of MAX7219 driver chip. The common cathode pin 4 of LTC-4727 goes to D4 pin of MAX7219. So, in order to turn on L1, L2, and L3 segments, D4 digit select pin of MAX7219 should be active. Here’s an example that shows how to interface this module with an Arduino board usinf the LedControl library.
#include "LedControl.h"
// Arduino Pin 7 to DIN, 6 to Clk, 5 to LOAD, no.of devices is 1
LedControl lc=LedControl(7,6,5,1);
void setup()
{
// Initialize the MAX7219 device
lc.shutdown(0,false); // Enable display
lc.setIntensity(0,10); // Set brightness level (0 is min, 15 is max)
lc.clearDisplay(0); // Clear display register
}
void loop()
{
lc.setDigit(0,0,4,true); // Display 4 to Digit 4, and turn DP on
lc.setDigit(0,1,3,true); // Display 3 to Digit 3, " "
lc.setDigit(0,2,2,true); // Display 2 to Digit 2, " "
lc.setDigit(0,3,1,true); // Display 1 to Digit 1, " "
lc.setDigit(0,4,7,true); // Turns L1, L2, and L3 on
delay(1000);
}
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Note that the DIN, CLK, and LOAD pins of the display are connected to Arduino pins 7, 6, and 5, respectively. For more details on MAX7219 device, see the original article.
For more detail: New version of MAX7219 based 4-digit serial seven segment LED display
- What is the main difference between the new SPI7SEGDISP4.40-1R and the previous version?
The new version features a better quality LTC-4727JS display with three extra LED segments useful for displaying time. - How are the common cathode terminals connected on the board?
Digit 1 through Digit 4 connect to D3, D2, D1, and D0 pins of the MAX7219, while the common cathode pin 4 connects to D4. - Which Arduino pins are used for DIN, CLK, and LOAD connections?
DIN connects to pin 7, CLK to pin 6, and LOAD to pin 5. - Can this module be used to display time formats like HH:MM or MM:SS?
Yes, the additional colon segments allow for displaying time in these formats. - What library is recommended for interfacing this module with an Arduino?
The LedControl library is used to interface the module with the Arduino board. - How do you activate the L1, L2, and L3 segments on this display?
You must make the D4 digit select pin of the MAX7219 active. - What is the range for setting brightness levels using the setIntensity function?
Brightness levels range from 0 (minimum) to 15 (maximum).
