Hi.
I want to add a start button to this project, so the stopwatch don't start on power up.:
https://www.sunfounder.com/learn/RFID_kit_V1_for_Arduino/lesson-17-stopwatch-4-digit-7-segment-display-rfid-v1-0-for-arduino.html
i would like to use pin 9 as a input, to start the stopwatch (instead of the decimal point), and then set a timer - and then stop the display after 10 minutes.
Is there anybody, who can help me ?
Thanks.
I just had a look at the Sunfounder code and bad news on the adding a button front, the code is loaded with calls to delay() that make any chance the code will see the button pressed, it will be late.
I wonder if Sunfounder put that code up to cause the least confusion for beginners but can't be sure. Perhaps arrays and loops and using byte instead of int to hold small numbers would only confuse beginners?
A byte takes 1 byte of RAM and an int takes 2. Arduino Uno only has 2048 bytes of RAM. It won't kill this sketch to waste RAM but the habit usually leads to a thread asking why a sketch keeps resetting itself.
FYI, a byte can hold from 0 to 255 while an int can hold from -32768 to 32767. Arduino pin numbers tend to be less than 100.
There are other 7-segment libraries around but I don't know for sure which will not block an added button/sensor.
Sunfounder has a forum, maybe the forum has better display code for that. Or maybe they'd trade hardware for a fix?
Give this mod a go, untested, wire a pushbutton between GND and pin A0:
/***************************************
name:Stopwatch
function: you can see the number increases by one per second on the 4-digit 7-segment display.
***********************************/
//Email:support@sunfounder.com
//Website:www.sunfounder.com
/**************************************/
#include <TimerOne.h>
//the pins of 4-digit 7-segment display attach to pin2-13 respectively
int a = 2;
int b = 3;
int c = 4;
int d = 5;
int e = 6;
int f = 7;
int g = 8;
int p = 9;
int d4 = 10;
int d3 = 11;
int d2 = 12;
int d1 = 13;
long n = 0;// n represents the value displayed on the LED display. For example, when n=0, 0000 is displayed. The maximum value is 9999.
int x = 100;
int del = 5;//Set del as 5; the value is the degree of fine tuning for the clock
int count = 0;//Set count=0. Here count is a count value that increases by 1 every 0.1 second, which means 1 second is counted when the value is 10
void setup()
{
//set all the pins of the LED display as output
pinMode(A0,INPUT_PULLUP); //<<<<<< inserted new line
pinMode(d1, OUTPUT);
pinMode(d2, OUTPUT);
pinMode(d3, OUTPUT);
pinMode(d4, OUTPUT);
pinMode(a, OUTPUT);
pinMode(b, OUTPUT);
pinMode(c, OUTPUT);
pinMode(d, OUTPUT);
pinMode(e, OUTPUT);
pinMode(f, OUTPUT);
pinMode(g, OUTPUT);
pinMode(p, OUTPUT);
Timer1.initialize(100000); // set a timer of length 100000 microseconds (or 0.1 sec - or 10Hz => the led will blink 5 times, 5 cycles of on-and-off, per second)
Timer1.attachInterrupt( add ); // attach the service routine here
while(digitalRead(A0) == true); //<<<<<< inserted new line
}
/***************************************/
void loop()
{
clearLEDs();//clear the 7-segment display screen
pickDigit(0);//Light up 7-segment display d1
pickNumber((n/1000));// get the value of thousand
delay(del);//delay 5ms
clearLEDs();//clear the 7-segment display screen
pickDigit(1);//Light up 7-segment display d2
pickNumber((n%1000)/100);// get the value of hundred
delay(del);//delay 5ms
clearLEDs();//clear the 7-segment display screen
pickDigit(2);//Light up 7-segment display d3
pickNumber(n%100/10);//get the value of ten
delay(del);//delay 5ms
clearLEDs();//clear the 7-segment display screen
pickDigit(3);//Light up 7-segment display d4
pickNumber(n%10);//Get the value of single digit
delay(del);//delay 5ms
if(millis > 600000UL) //<<<<<< inserted new lines (2)
while(true); loop here forever, press reset button to continue
}
/**************************************/
void pickDigit(int x) //light up a 7-segment display
{
//The 7-segment LED display is a common-cathode one. So also use digitalWrite to set d1 as high and the LED will go out
digitalWrite(d1, HIGH);
digitalWrite(d2, HIGH);
digitalWrite(d3, HIGH);
digitalWrite(d4, HIGH);
switch(x)
{
case 0:
digitalWrite(d1, LOW);//Light d1 up
break;
case 1:
digitalWrite(d2, LOW); //Light d2 up
break;
case 2:
digitalWrite(d3, LOW); //Light d3 up
break;
default:
digitalWrite(d4, LOW); //Light d4 up
break;
}
}
//The function is to control the 7-segment LED display to display numbers. Here x is the number to be displayed. It is an integer from 0 to 9
void pickNumber(int x)
{
switch(x)
{
default:
zero();
break;
case 1:
one();
break;
case 2:
two();
break;
case 3:
three();
break;
case 4:
four();
break;
case 5:
five();
break;
case 6:
six();
break;
case 7:
seven();
break;
case 8:
eight();
break;
case 9:
nine();
break;
}
}
void clearLEDs() //clear the 7-segment display screen
{
digitalWrite(a, LOW);
digitalWrite(b, LOW);
digitalWrite(c, LOW);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, LOW);
digitalWrite(p, LOW);
}
void zero() //the 7-segment led display 0
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, HIGH);
digitalWrite(g, LOW);
}
void one() //the 7-segment led display 1
{
digitalWrite(a, LOW);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, LOW);
}
void two() //the 7-segment led display 2
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, LOW);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, LOW);
digitalWrite(g, HIGH);
}
void three() //the 7-segment led display 3
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, HIGH);
}
void four() //the 7-segment led display 4
{
digitalWrite(a, LOW);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
}
void five() //the 7-segment led display 5
{
digitalWrite(a, HIGH);
digitalWrite(b, LOW);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, LOW);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
}
void six() //the 7-segment led display 6
{
digitalWrite(a, HIGH);
digitalWrite(b, LOW);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
}
void seven() //the 7-segment led display 7
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, LOW);
}
void eight() //the 7-segment led display 8
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
}
void nine() //the 7-segment led display 9
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, LOW);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
}
/*******************************************/
void add()
{
// Toggle LED
count ++;
if(count == 10)
{
count = 0;
n++;
if(n == 10000)
{
n = 0;
}
}
}
Thanks for the code - I get a error on that:
error: 'here' was not declared in this scope
while(true); loop; here forever, press reset button to continue
I think, that I will install a off-delay timer in front of the power supply, then I wont have to change the code 
loop here forever, press reset button to continue
Make this line a comment
UKHeliBob:
loop here forever, press reset button to continueMake this line a comment
This kind of works - the display is cleared (8888), until I make the start - but the count-up timer counts in the backgrund, so when I make the start, it starts on ex. 00:32, not on zero.
Thanks for the help - I'll just make a start relay with a off-delay on the power supply.