Arduino Uno zero crossing strange behavior

Projects Programming
1

Hi,

I'm currently trying to replace a defect dimmer motherboard by an Arduino Uno.
i've done a very simple program, to start :

int pin=10;


void setup()
{
  pinMode(pin, OUTPUT);
  attachInterrupt(0, zerocross, RISING);
}
void loop()
  {
  }

void zerocross()
  {
  delayMicroseconds(7000);
  digitalWrite(pin, HIGH);
  delayMicroseconds(8.33);
  digitalWrite(pin, LOW);  
}

I live in France so delay must be between 1/60s (full) and 1/whatever dimming range you want second (60Hz).

the program works fine except that the light blinks ramdomly. What is strange is that I have the same trouble if I replace the arduino by a correctly programmed PC paralell port.

Is there something I don't understand or the electronic part is probably involved ?

Thank you very much,

Best regards

GrAaL

2

60Hz in france? strange indeed.. all EU has 50Hz.

Also you should brace the intrerrupt routine with nointerrupts() interrupts() statements.
This makes no sense:

delayMicroseconds(8.33)

delayMicroseconds takes an integer as argument, not a floating point value. The floating point value i converted to integer, a waste of time (unless the compiler handles it)

3

Hi,

I've added noInterrupts() and Interrupts() and change 8.33 to 10 :

 noInterrupts();
   delayMicroseconds(7000);
   digitalWrite(pin, HIGH);
   delayMicroseconds(10);
   digitalWrite(pin, LOW);
   interrupts();

but I have exactly the same issue : dimming seems fine but the lamp flashes 3-5 times ni 10 seconds. As long as I can see, it's completely random.
The PC version using the paralell port was doing the same but I was thinking that it was due to other system paralell tasks.

thank you for your help !

Best regards,

GrAaL

4

Do not do delays in an interrupt!
If the zero crossing occurs, set a global flag and get out.
Use loop() to toggle the LED.

5

Hi,

I'ave already try that first in fact but without disabling interrupt during the "if".
It works fine now, thank you very much !

Here is that code if anyone needs it :

int pin=10;
volatile int dimmer_trigger=0;
void setup()
{
  pinMode(pin, OUTPUT);
  attachInterrupt(0, zerocross, RISING);
}
void loop()
  {
   noInterrupts();
   delayMicroseconds(80);
   dimmer_trigger++;
   if ( dimmer_trigger == 75 )
     {
     digitalWrite(pin, HIGH);
     }
   else
     {
     digitalWrite(pin, LOW);
     }
   interrupts();   

  }

void zerocross()
  {
  dimmer_trigger=0;
  }

Best regards,

GrAaL