How to make led fade out in 5s using PWM in arduino - arduino

Question

How to make a led fade out in 5s using PWM in arduino. I wrote this function, it didn't work. I try to call this function.
const int minPWM = 0;
const int maxPWM = 255;
int fadeValue = 255;
int fadeIncrement = 5;
unsigned long previousFadeMillis;
int fadeInterval = 50;
void setLightPWM(unsigned long thisMillis) {
if (thisMillis - previousFadeMillis >= fadeInterval) {
fadeValue = fadeValue - fadeIncrement;
if (fadeValue <= minPWM) {
// At min, limit and change direction
fadeValue = minPWM;
}
analogWrite(garageLED, fadeValue);
previousFadeMillis = thisMillis;
}
return;
}
Also, I wrote this line in loop()
unsigned long currentMillis = millis();
setLightPWM(currentMillis);

Answer 1

boolean initFade;
long startTime;
void setup(){
startTime=0;
initFade=false;
}
void loop(){
if(initFade){
startTime = millis();
initFade=false;
}
initFade = customizedFade;
}
boolean customizedFade(long fadeTime){
long timePassed = millis()-startTime;
if(timePassed < fadeTime ){
analogWrite(LEDPIN, map(timePassed,0,5000,255,0));
return false;
}
else{
return true;
}
}

Answer 2

I assumed that this code is complete (along with a pinMode(garageLED, OUTPUT) call and the definition of garageLED), and that the idea is to make an LED fade in and out (as you wrote in a comment "at min [...] change direction".
If my assumptions are right, then your code is missing the ability to invert the fade change. When it goes below the minimum it is set to the minimum value, but then nothing happens. At each further call it is set again to the minimum value.
So if the idea was to fade in and out you need to change the "fading direction":
if (fadeValue <= minPWM) {
// At min, limit and change direction
fadeValue = minPWM;
fadeIncrement = - fadeIncrement; //<-- Invert the value of "fadeIncrement"
}
and then the same thing when hitting the maximum value:
if (fadeValue >= maxPWM) {
// At max, limit and change direction
fadeValue = maxPWM;
fadeIncrement = - fadeIncrement; //<-- Invert the value of "fadeIncrement"
}
If the idea is to fade out, then suddenly fully turn on and fade out again, then you only need to set to maximum value when hitting the minimum:
if (fadeValue <= minPWM) {
// At min, limit and change direction
fadeValue = maxPWM;
}
Here is a working sketch whit your code plus some extra lines and my changes. All what I added or modified is marked with a // <-- symbol.
const int garageLED = 5; // <-- added to make the sketch work
const int minPWM = 0;
const int maxPWM = 255;
int fadeValue = 255;
int fadeIncrement = 1; // <-- why not use the smallest increment value?
unsigned long previousFadeMillis;
int fadeInterval = 20; // <-- 20ms interval to get a 5s fade time with (fadeIncrement == 1)
// (fadeInterval = fadeTime/fadeSteps), where fadeTime = 5000 ms
// and fadeSteps = (maxPWM - minPWM)/fadeIncrement.
// So in this case fadeInterval = 5000/((255 - 0)/1) = 5000/255 =~ 19,6
void setLightPWM(unsigned long thisMillis) {
if (thisMillis - previousFadeMillis >= fadeInterval) {
fadeValue = fadeValue - fadeIncrement;
if (fadeValue <= minPWM) {
// At min, limit and change direction
fadeValue = minPWM;
fadeIncrement = - fadeIncrement; //<-- Invert the value of "fadeIncrement"
}
if (fadeValue >= maxPWM) { //<-- Added if block
// At max, limit and change direction
fadeValue = maxPWM;
fadeIncrement = - fadeIncrement; //<-- Invert the value of "fadeIncrement"
}
analogWrite(garageLED, fadeValue);
previousFadeMillis = thisMillis;
}
return;
}
void setup() { // <-- added to make the sketch work
pinMode(garageLED, OUTPUT); // <--
} // <--
void loop() {
unsigned long currentMillis = millis();
setLightPWM(currentMillis);
}