I got myself a cheap 4 digits 7-led display and I thought I would spend a few mns playing with it and documenting it.
12 pins : 8 for the segments (including the dots), 4 for each digit
Top row : 1, a, f, 2, 3, b
Bottomw row: e, d, dp, c, g, 4
I decided to use the Sevseg arduino library.
More about this library here.
The wiring is then as is :
Arduino pins -> 4digits display pins
2->1
6->a
11->f
3->2
4->3
7->b
10->e
9->d
13->dp
8->c
12->g
5->4
Below the schema
Note that this is a lot of digital IO’s used. A future article could focus on reducing the number of IO’s needed.
Below the arduino sketch (from the example provided with the sevseg library)
/*Written by Dean Reading, 2012. deanreading@hotmail.com
This example is a centi-second counter to demonstrate the
use of my SevSeg library.
*/
#include "SevSeg.h"
//Create an instance of the object.
SevSeg sevseg;
//Create global variables
unsigned long timer;
int CentSec=0;
void setup() {
//I am using a common anode display, with the digit pins connected
//from 2-5 and the segment pins connected from 6-13
sevseg.Begin(1,2,3,4,5,6,7,8,9,10,11,12,13);
//Set the desired brightness (0 to 100);
sevseg.Brightness(50);
timer=millis();
}
void loop() {
//Produce an output on the display
sevseg.PrintOutput();
//Check if 10ms has elapsed
unsigned long mils=millis();
if (mils-timer>=10) {
timer=mils;
CentSec++;
if (CentSec==10000) { // Reset to 0 after counting for 100 seconds.
CentSec=0;
}
//Update the number to be displayed, with a decimal
//place in the correct position.
sevseg.NewNum(CentSec,(byte) 2);
}
}
9 Responses to “Arduino : 4 digits 7-led display”
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Hi !!!
Be so kind to explain how to reduce the number of I / O pins?
Greetings and thanks in advance.
I am planning on using a shift register (74hc595) as used in that article.
OK
Thanks for the reply, when you have it, Could you post how to do?
Regards and thanks again.
will do !
I would love to use the SevSeg Library with a shift register for the 7 segments plus decimal point. I think you would have to modify SevSeg.cpp
Any luck?
I dont understand : the example already provide an example with with a dot ?
//Update the number to be displayed, with a decimal
//place in the correct position.
sevseg.NewNum(CentSec,(byte) 2);
Yes it has a decimal. But what about using a Shift Register with the SevSeg Library and 7 segment display.
I think you would have to modify SevSeg.cpp
In the code we can see that you use common anode display. I found that with common anode the resistor should be on the cathode. Can you explain/justify why you put resistors on anode. How did you calculate resistor value (330ohms) ?
You are probably right about the anode and to be fair i did not calculate the resistor value but just put one in to be safe.
I know…i Know… not very clean 🙂