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About triac BT139

Question asked by Shivani Umredkar on Aug 21, 2019

Hi, I am working on home automation based product. for switching i have designed small circuit using BT139 triac and driver IC MOC3021. circuit works well, I mean normal switching but currently I facing some issue in my circuit. this is the situation when I am ringing my door bell lights start to blink. I tried different test cases to resolve this issue. My design is the combination of mechanical relay and BT139 switching. and the common terminal is load where mechanical relay NC terminal connected and triac T2 terminal connected. 

Test cases I tried with door bell. (Door bell not connected with my kit but the same switch board)

- I tried with snubber circuit in triac reccomended according to datasheet (39Ohm 1W and 0.01uF capacitor) but no effect.

- I tried with snubber circuit for MOC3021 480ohm in series with 330ohm on T2 terminal and in between 0.05uf capacitor x rated.

- I read about hybrid relay I thought these problem happening due to emi interference because on cro i am actually getting spikes whenever circuit restart (I mean when I switch off and  on) my applience get blink ones. so according to this i connect 10uH inductor on output. second to remove  spikes I tried with MOV of 440K.

- In my circuit on T2 - load connected and on T1 - line connected even i tried to interchange it.

- without triac with only mechanical relay this problem not occure.


These all are the test cases I performed but didnt get any specific solution and come to the point there may be leakage current in triac. please provide me the technical support how can i remove these spikes which are coming on load end. All the required details I have attached.


Thanks looking for your support