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Topic: How to catch 7 segment signal? (Read 1 time) previous topic - next topic


Jun 20, 2013, 09:33 am Last Edit: Jun 20, 2013, 12:18 pm by matsuo Reason: 1
Hello !.

             I need to read 7 segment signal of  9 digits then sent print to serial port
*7 segment , common Anode.

my circuit ****** I just test 1 digit only
1. A-G legs of  7 segment connect to  (-)  of Opto , ( +) leg of Opto to +5V
2. common Anode  leg of  7 segment (Digit)  connect to (+) of Opto ,( +) leg of Opto to Gnd
3. Output of Opto connect to 6-12  (A-G) legs of  Arduino  and Pull-up with +5V
4. Output of Opto (Common Cathod ) connect to D2 of Arduino.
This is my code but it don't work.
Code: [Select]
#include <LiquidCrystal.h>
#include <EEPROM.h>
//#include <EEPROMAnything.h>

LiquidCrystal lcd(22, 24, 26, 28, 30, 32);
int buttonPins[] = {6,7,8,9,10,11,12} ;
int buttonStates[7];      
int i;
int A=0;
int B=0;
int C=0;
int D=0;
int E=0;
int F=0;
int G=0;
String total="";

void setup() {
for (i=0; i<7; i++)
  pinMode(buttonPins[i], INPUT);    
 pinMode(4, INPUT);
 pinMode(5, INPUT);
 lcd.begin(16, 2);


void loop() {
 val1 = digitalRead(2);  // read input value
if (val1 == LOW )

 buttonStates[0] = digitalRead(buttonPins[0]);
 buttonStates[1] = digitalRead(buttonPins[1]);
 buttonStates[2] = digitalRead(buttonPins[2]);
 buttonStates[3] = digitalRead(buttonPins[3]);
 buttonStates[4] = digitalRead(buttonPins[4]);
 buttonStates[5] = digitalRead(buttonPins[5]);
 buttonStates[6] = digitalRead(buttonPins[6]);                          
if (val1 == HIGH )
    A= EEPROM.read(6);
    B= EEPROM.read(5);
    C= EEPROM.read(4);
    D= EEPROM.read(3);
    E= EEPROM.read(2);
    F= EEPROM.read(1);
    G= EEPROM.read(0);
    lcd.setCursor(0, 1);


* I tried to sent "9"  to 7 segment but my program show as below.


What is the refresh rate on the display?

Are the optoisolators fast enough to catch the pulses?

I suspect that the digitalReads() might be too slow to catch all of the bits before they change.  You might want to use Direct Register Access so you can grab all 8 pins at once.

You probably shouldn't use EEPROM cells for variables since they have a limited lifetime (100,000 writes?).

Your wiring will allow you to capture one digit at a time but gives you no indication of which digit you are getting.  You should probably have a separate  input pin for one of the digits so you can synchronize your (to be implemented) digit counter.
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Jul 15, 2013, 12:22 pm Last Edit: Jul 15, 2013, 12:24 pm by matsuo Reason: 1
Thanks you johnwasser for advise to me. Now I can chatch signal 7 segment to display on my app (Visual basic)
but sometime my program wrong display as my photo, I think have noise in circuit .

This is my circuit ,Could you modify something for reduce noise ?

This is my app


Hello Matsuo!,

This issue is really interesting, I have the same problem when reading data from a 7 segments.
How did you fix it?
Could you share your code?

Thank you!!


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