I have used this as AC dimmer and it worked fine. Only issue is missing heat sink on the TRIAC.

I tried to make it work just as a dimmer and I couldn't

Seems to be working.

#define DETECT 2 //zero cross detect
#define GATE 9 //TRIAC gate
#define PULSE 500 //trigger pulse width (counts)
int brightness = 0;
#include
void setup(void)
{
pinMode(DETECT, INPUT); //zero cross detect
digitalWrite(DETECT, HIGH); //enable pull-up resistor
pinMode(GATE, OUTPUT); //TRIAC gate control
attachInterrupt(0, zeroCrossingInterrupt, RISING);
Timer1.attachInterrupt(timer1_interrupt); // blinkLED to run every 0.15 seconds
Serial.begin(9600);
}
void loop(void)
{
int variable_value = analogRead(A0);
brightness = map(variable_value, 0, 1023, 0, 9000);
if (brightness > 7500) detachInterrupt(0); // disconnect interrrupt
else attachInterrupt(0, zeroCrossingInterrupt, RISING); // connect interrupt
Serial.println(brightness);
delay(100);
}
//////////////////////////
void zeroCrossingInterrupt() { //zero cross detect interrupt
Timer1.initialize(brightness);
}
///////////////////////////////////////
int state = 0;
void timer1_interrupt(void) // timer interrupt to triger gate
{
if (state == 0) {
state = 1; // turn on gate
Timer1.initialize(PULSE);
digitalWrite(GATE, HIGH);
}
else {
state = 0; // turn off gate
Timer1.stop();
digitalWrite(GATE, LOW);
}
}

Kindly attach the heat sink in it .... it is causing noise