Dimmer AC Circuit Resistor burns

if we change the terminals and when I start dimming then the resistor connected to MT2 is getting burnt whether its 1k,10k,10k1/2W anything

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andre_teprom said:

Are you using any strongly reactive load, such as a motor ?
If yes, it is missing a snubber on your circuit.

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FvM said:

Resistors > 2k will probably been overloaded and shouldn't been used. If 1k resistor burns, you have either a problem with non-triggering triac (defective or different type than BT138 with high trigger threshold) or a shorted capacitor. The capacitor must be rated for 250 VAC or at least 630 VDC.

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KlausST said:

We don't see how you drive the MOC's LED.

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int AC_LOAD = 3; // Output to Opto Triac pin
int dimming = 128; // Dimming level (0-128) 0 = ON, 128 = OFF
void setup()
{
Serial.begin(9600);
pinMode(AC_LOAD, OUTPUT); // Set the AC Load as output
attachInterrupt(digitalPinToInterrupt(2), zero_crosss_int, RISING); // Choose the zero cross interrupt
}
void zero_crosss_int() // function to be fired at the zero crossing to dim the light
{
// Firing angle calculation :: 50Hz-> 10ms (1/2 Cycle)
// (10000us - 10us) / 128 = 75 (Approx)
int dimtime = (75*dimming);
delayMicroseconds(dimtime); // Off cycle
digitalWrite(AC_LOAD, HIGH); // triac firing
delayMicroseconds(10); // triac On propogation delay
digitalWrite(AC_LOAD, LOW); // triac Off
}
void loop()
{
dimming = 90;
delay(7000);
dimming = 50;
delay(7000);
dimming = 20;
delay(7000);
}

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MOCs LED is driven from the controller using program

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hey @FvM, the cap 0.1uF should be 275VAC one?

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KlausST said:

Hi,

--> use a scope.
In cas eyou don´t have one, then buy one or lend one.


Klaus

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