keep getting gate resistor of SCR burn out

[nitinjndal]

Hi,

I am trying to control a CFL light through a Micro-controller but the gate resistor of SCR is burning out. I have tried many things but could not solve it. I have also tried by cut short the circuit by just giving supply at the input of opto-isolator but still the gate resistor R1 burning out. Can you tell where I am making mistake? I have attached snapshot of the schematic. Thanks in advance.

 

[rudr_p]

https://www.eetimes.com/document.asp?doc_id=1272528
I hope this helps.
There are dimmable and non dimmable lamps see if you have the right one.

 

[schmitt trigger]

The circuit as drawn appears to be OK.
Test it first with an incandescent lamp.

 

[nitinjndal]

Hi. Thanks for the advice. I have tried it by using incandescent bulb, but still I the resistor burnt. Any other thing which I can check?

 

[Anna Conda]

swap pins 1 & 2 on Triac.

 

[nitinjndal]

I have tried by swapping connections but the triac does not even switch ON if I swap the connections of it.

 

[chuckey]

mains via the MOC then 100 ohms to gate of triac, Err that is a lot of current. I would think 10 mA would be enough, so R = 230V/.01 ~ 22K?
Frank

 

[mtwieg]

mains via the MOC then 100 ohms to gate of triac, Err that is a lot of current. I would think 10 mA would be enough, so R = 230V/.01 ~ 22K?
Frank

Well that would give 10mA at peak line voltage, you probably want to fire earlier. But yeah that resistor should be at least 1k.

 

[FvM]

BT136 trigger current can be as high as 35 mA. So 1k would be a quite high value. A better solution, which is explicitely required for inductive loads, is a RCR circuit where the peak trigger current is supplied by the capacitor.

 

[chuckey]

FvM has hit it on the head, power in a 1K, 230^2/1K ~ 50W!! :-(
Frank

 

[nitinjndal]

Hi,

Can you please tell me how to implement this RCR circuit which you are telling.

Thanks.

 

[FvM]

See https://www.edaboard.com/threads/162207/#post686270