Triac Switching Circuit Problem

HI to all,



I had attached the Triac switching circuit here, I removed entire DC supply in the connector(CON2) and also a signal pins (CON9). Only AC supply is connected in the board. While Im Switching AC supply ON and OFF, during that time i getting the flickering in power ON led and output led (ie., LD9 and LD2 respectively). So i suspected with MOC3021 IC and I removed it and checked, now LD9 IS FLICKERING and LD2 IS NOT FLICKERING. I dont know how the LED is flickering during switch ON and OFF the AC supply.

Please let me know the reason for this flickering..

Thanks in advance,
anboli.c

There is no power source to the LEDs while the connectors is removed so you must have leakage from the AC side of the circuit. Are you sure you have the MOC3021 wired correctly and the Earth/Neutral are not crossed over?

Brian.

Also check that you didn't accidentally switch the terminals of your TRIAC, this also caused me a lot of trouble in a previous project... and very hard to pinpoint the problem.

Switching the triac terminals wouldn't power up the DC side of the MOC3021 but there is one other thing to check that I should have mentioned - if the triac mounting tab isn't isolated, make sure you haven't shorted it through it's mounting screw to something else.

Brian.

betwixt said:

There is no power source to the LEDs while the connectors is removed so you must have leakage from the AC side of the circuit. Are you sure you have the MOC3021 wired correctly and the Earth/Neutral are not crossed over?

Brian.

Click to expand...

Thanks Brian,
Here AC Earth is idle only. there is no interference between earth and neutral.

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betwixt said:

Switching the triac terminals wouldn't power up the DC side of the MOC3021 but there is one other thing to check that I should have mentioned - if the triac mounting tab isn't isolated, make sure you haven't shorted it through it's mounting screw to something else.

Brian.

Click to expand...

Yeah i mounted the TRIAC through Mounting screw in the board. Whether i need to check the Board, after removing the mounting screw of the triac.

On many triacs the tab is joined to the center pin so perhaps that is where the power leakage path is.

Brian.

I removed the Heat Sink from the board and tested it, problem coming but not like previous condition. And i removed the 230V Actuator from the board, there is no flickering in the board, while connecting the Actuator its get flicker. what shall i have do now? how can i protect the circuit? Already i used the snubber's in the circuit. Please help me to find out the problem specifically.

The only remaining causes I can think of are capacitive coupling or inductive coupling. You must have a very bad board board layout to be able to flash LEDs on an isolated supply though. Can you post a photograph of what you have built so we can see.

Brian.