fade LEDs

Forum 2005-2010 (read only) Software Syntax & Programs
1

Hi,

Sorry for opening a new thread. I think in my old thread my problem description was a bit confusing.

I have two LEDs and want to fade them out. But want the 2nd LED to start fading out when the first is about half way faded out.

I really don't know how to do this.

Any help please..........

2

Look in the tutorials for the "blink without delay" example, and "fade", instead of "blink".

3

I know how to fade them, but not how to start fading the 2nd one while the first one is still fading.

4

Maybe you can post some code you're using to fade one LED.
That way we can help you fade the second one in the most similar method.

5

#define NUMLEDS 2
#define BUTTON 13

int val = 0;
int oldVal = 0;
int state = 0;
int led[NUMLEDS]={11,10};

void setup(){

for(int i = 0; i<NUMLEDS; i++){
pinMode(led*,OUTPUT);*

  • }*
  • pinMode(BUTTON,INPUT);*
  • Serial.begin(9600);*
    }
    void loop(){
  • val = digitalRead(BUTTON);*
  • Serial.println(val);*
  • if((val==HIGH)&&(oldVal==LOW)){*
  • state=1-state;*
  • delay(10);*
  • }*
  • oldVal=val;*
  • if(state==1){*
  • for(int i = 0; i<NUMLEDS; i++){*
    _ digitalWrite(led*,HIGH);*_

* }*
* delay(3000);*
_ for(int i = 2*255; i>=0; i--){_

* fading1(i);*
* //Serial.println(i);*
* }*
* state=0;*
* }*
* else{*
* for(int i = 0; i<6; i++){*
_ digitalWrite(led*,LOW);
 }
 }
}*
void fading1(int i){_

* int value1 = i-255;*
* int value2 = i;*

* analogWrite(led[0],value1);*
* Serial.println(value1);*

* if (value1 < 128){*
* analogWrite(led[1],value2);*
* }*
* if (value1<1){*
* value1=0;*
* } *

* delay(10);*
}

6 
for (int light = 255; light <=0; --light) {
  analogWrite (LED1_PIN, light);
  if (light < 128) {
    analogWrite (LED2_PIN, light * 2);
  }
  delay (100);
}
7

thanks.

now the 2nd LED starts fading when the 1st LED reaches 128 but unfortunately they reach 0 at the same time.

When the 1st LED is at 0 I want the 2nd to be at 128 fading down to 0.

8

I've copied the essential parts of your code and used it as a base for this code that seems to do what you requested.

int led[]={5,6};

void setup() {
  Serial.begin(9600);
  pinMode(led[0], OUTPUT);
  pinMode(led[1], OUTPUT);
}

void loop() {
  for(int i=255 + 127; i>=0; i--) {
    fading1(i);
  }
}

void fading1(int i) {
  int value1 = min(255, max(0, i));
  int value2 = min(255, max(0, i - 127));
  
  analogWrite(led[0], value1);
  Serial.println(value1);
  
  analogWrite(led[1], value2);
  Serial.println(value2);
  
  delay(10);
}

P.S. if you put your code between [ code ] and [ /code ] it's easier read

9

hey thank you so much. that did it.
min() and max() just wonderful.

10

Just be aware when using min/max that it might seem reversed in some cases.

This one is straight forward:
int c = max(a, b); // c becomes the greater of a and b

But in this case, it's a bit odd:
int c = min(255, a); // c becomes a, with a maximum of 255
int d = max(0, b); // d becomes b, with a minimum of 0